Segui questo link per vedere altri tipi di pubblicazioni sul tema: Visual perception.
Tesi sul tema "Visual perception"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Visual perception".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Deplancke, Antoine. "Approche psychophysique des dissociations perception-action : effet de la détection de distracteurs au seuil sur l’atteinte de cibles visuelles". Thesis, Lille 3, 2012. http://www.theses.fr/2012LIL30033/document.
Testo completoAbstract (sommario):
La théorie dominante suggérant une séparation entre une vision consciente pour la perception et une vision non consciente pour l'action au sein du système visuel fut particulièrement discutée au cours des dernières décennies. La thèse défendue ici se positionne dans le cadre d'une approche alternative reposant sur une évaluation conjointe des réponses motrice et perceptive en présence de stimuli au seuil perceptif. Les travaux réalisés dans ce contexte ont initialement porté sur les temps de réaction et ont contribué au développement d'un modèle psychophysique postulant que les réponses perceptives et motrices dépendraient d'un signal sensoriel unique mais de seuils de décision spécifiques. Les trois études réalisées au cours de cette thèse ont permis de tester ces propositions à partir de travaux portant sur le contrôle moteur manuel. Tout en confirmant une forte association entre les traitements visuels pour la perception et pour l'action, ces travaux ont permis de mettre en évidence un rôle important des conditions expérimentales (par exemple le contraste des stimuli et la présence ou non d'un masque visuel) dans les résultats obtenus. Les résultats se sont révélés compatibles avec les modèles neurophysiologiques du masquage visuel qui postulent que la réponse neurale à une stimulation visuelle est constituée d'une vague d'activation feedforward associée à la présence physique de la stimulation et de boucles de rétroaction liées à la perception consciente de celle-ci. Nos travaux ont également permis d'adapter au contrôle moteur manuel le modèle de décision à signal unique initialement développé dans le cadre des études portant sur les temps de réactionThe dominant position of a separation between a conscious vision for perception and an unconscious vision for action within the visual system has been particularly discussed in the last decades. The present dissertation is to be placed in the context of an alternative approach consisting in evaluating jointly both perceptual and motor responses in the presence of near-treshold visual stimuli. Previous work within this framework, which have mainly concerned reaction times, have contributed to develop a psychophysical model in which perceptual and motor decision are taken relatively to the same single incoming signal but are based on different tresholds. The three studies conducting during this PhD aimed to testing these proposals in experiments involving manual motor control. While confirming the strong link between perceptual and motor processing within the visual system, the results obtained in these studies underlined the importance of experimental parameters such as the contrast of the stimuli and the presence of visual masks. These results are congruent with neurophysiological models of visual masking, which postulate that the neural response to a visual stimulus is composed of a transient feedforward sweep of activation related to the presence of as stimulus and recurrent feedback loops linked to the conscious perception of this stimulus. Our work also led to the adaptation to manual motor control of the single signal decisional model initially developed on the basis of reaction time studies
2
Porporino, Mafalda. "Developmental differences in global and local perception : is global perception more attention demanding than local perception". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30796.
Testo completoAbstract (sommario):
The primary purpose of the present study was to examine various aspects of local and global perception in groups of children and young adults with average ages of 6, 8, 10, 12, and 22 years. The aspects examined included developmental differences in RT for local and global visual information, the influence of filtering on global and local perception, and role of distracter congruency and compatibility on processing local and global stimuli. At a general level, the findings revealed that participants processed global faster than local stimuli. With the presence of distracters, 6 and 8-year-old participants demonstrated slower RTs for global targets relative to local targets. Distracter congruency or compatibility did not differentially affect global and local processing. However, congruency did appear to be related to differential performance for 6-year old males versus females. These results indicate that the underlying processes involved in global and local perception may be separate, with global perception relying on attentional mechanisms to a greater extent than local perception.
3
Shin, Myoung Ju. "Visual orienting and conscious perception". Thesis, University of Auckland, 2012. http://hdl.handle.net/2292/19397.
Testo completoAbstract (sommario):
Much research supports the dichotomy model of visual covert orienting which suggests that attention shifting occurs either exogenously or endogenously. The present study attempts to suggest an alternative model that can accommodate evidence of endogenously cued orienting that may not necessarily involve consciousness. The first part of the present study (Experiment 1-3) examined whether or not the perceptual awareness of visual cue stimuli is essential in Posner���s cue-target orienting paradigm. Lowering the cue luminance had differential effects in orienting and cue identification tasks, in that the performance in the orienting task was relatively unimpaired in comparison with the performance in the cue identification task which was greatly affected by the decrease in the cue luminance. It was suggested that the orienting system uses the dorsal visual pathway, which is resilient to luminance decrease. In Experiment 4, a flicker adaptation procedure was included before the orienting task trials in order to over stimulate the M pathway which has been suggested to be important in luminance contrast processing and in orienting. The flicker adaptation affected the orienting process suggesting the involvement of the M pathway in the attentional mechanism, but contrary to hypothesis the effect was facilitatory rather than inhibitory. Lastly, the effects of the eccentricity (peripheral or central, Experiment 5), number (single or double, Experiment 5) and the size (big or small, Experiment 6) of visually symmetric cues on visual orienting were investigated. The results showed that neither the eccentricity nor the size of the cues interacted with cue validity. It was suggested that the attentional system first uses the spatial correspondence between cue and target in visual orienting. This hypothesis was further explained in terms of the visual orienting system exploiting both space-based and symbolic-meaning-based attention strategies depending on the efficiency of each strategy in a given task. The findings in the current study show evidence against the endogenous-exogenous dichotomy attentional model and suggest the necessity of an attentional model that accommodates a form of orienting that is neither purely exogenous nor purely endogenous.
4
Michel, Rachel Keyes. "Visual perception, search, and attention". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/29580.
Testo completo
5
Niall, Keith. "Projective invariance and visual perception". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75782.
Testo completoAbstract (sommario):
Six experiments tested the assumption that, in visual perception, observers have reliable and direct access to the equivalence of shapes in projective geometry (I call this "the invariance hypothesis in the theory of shape constancy"). This assumption has been made in the study of vision since Helmholtz's time. Two experiments tested recognition of the projective equivalence of planar shapes. In another four experiments, subjects estimated the apparent shape of a solid object from different perspectives. Departure from projective equivalence was assessed in each study by measuring the cross ratio for the plane. This measure of projective invariance is new to perceptual research. Projective equivalence was not found to be perceived uniformly in any of the studies. A significant effect of change in perspective was found in each study. These results were construed as supporting the classical theory of depth cues against the invariance hypothesis.
6
Chan, Y. M. "Depth perception in visual images". Thesis, University of Brighton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380238.
Testo completo
7
Sorensen, Robyn Elizabeth. "The perception of visual symmetry". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624479.
Testo completo
8
Carlin, Patricia. "On symmetry in visual perception". Thesis, University of Stirling, 1996. http://hdl.handle.net/1893/1777.
Testo completoAbstract (sommario):
This thesis is concerned with the role of symmetry in low-level image segmentation. Early detection of local image properties that could indicate the presence of an object would be useful in segmentation, and it is proposed here that approximate bilateral symmetry, which is common to many natural and man made objects, is a candidate local property. To be useful in low-level image segmentation the representation of symmetry must be relatively robust to noise interference, and the symmetry must be detectable without prior knowledge of the location and orientation of the pattern axis. The experiments reported here investigated whether bilateral symmetry can be detected with and without knowledge of the axis of symmetry, in several different types of pattern. The pattern properties found to aid symmetry detection in random dot patterns were the presence of compound features, formed from locally dense clusters of dots, and contrast uniformity across the axis. In the second group of experiments, stimuli were designed to enhance the features found to be important for global symmetry detection. The pattern elements were enlarged, and grey level was varied between matched pairs, thereby making each pair distinctive. Symmetry detection was found to be robust to variation in the size of matched elements, but was disrupted by contrast variation within pairs. It was concluded that the global pattern structure is contained in the parallelism between extended, cross axis regions of uniform contrast. In the third group of experiments, detection performance was found to improve when the parallel structure was strengthened by the presence of matched strings, rather than pairs of elements. It is argued that elongation, parallelism, and approximate alignment between pattern constituents are visual properties that are both presegmentally detectable, and sufficient for the representation of global symmetric structure. A simple computational property of these patterns is described.
9
RAHMAN, SHAHNUR. "Visual Perception in Autonomous Vehicles". Thesis, KTH, Hållbarhet och industriell dynamik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189346.
Testo completoAbstract (sommario):
The human factor accounts for nine out of ten out of all traffic accidents, and because more vehicles are being deployed on the roads, the number of accidents will increase. Because of this, various automated functions have been implemented in vehicles in order to minimize the human factor in driving. In recent year, this development has accelerated and vehicles able to perform the complete driving task without any human assistance have begun to emerge from different projects around the world. However, the autonomous vehicle still has many barriers to overcome before safe driving in traffic becomes a reality. One of these barriers is the difficulty to visually perceive the surrounding. This is partly because of the fact that something can cover the camera sensors, but it is also problematic to translate the perceived data, that the sensors are collecting, into something valuable for the passenger. The situation could be improved if wireless communications were available to the autonomous vehicle. Instead of trying to understand the surrounding by the use of camera sensors, the autonomous vehicle could obtain the necessary data via wireless communication, which was the subject of this study. The study showed that wireless communication will be significant for the autonomous vehicle in the future. The conclusion is based on the fact that wireless communication was a solution in other transport systems that have had the similar barrier as for the autonomous vehicle. There are also plans on managing the barrier via wireless communication in pilot projects related to autonomous vehicles.Den mänskliga faktorn står för nio av tio utav alla trafikolyckor, och eftersom att allt fler fordon kommer ut på vägarna så leder det till att olycksantalet ökar. På grund av detta så har olika automatiserade funktioner applicerats i fordonet för att undvika den mänskliga faktorn i körningen. Denna utveckling har accelererat och fordon som ska kunna utföra hela det dynamiska framförandet utan mänsklig assistans har börjat utvecklas i olika projekt runt om i världen. Dock så har det autonoma fordonet många barriärer kvar att övervinna, för säkert framförande, varav en av dessa barriärer är fordonets förmåga att visuellt uppfatta omgivningen. Dels genom att något kan täcka kamerasensorerna men även att kunna omsätta det sensorerna uppfattar till något värdefullt för passageraren. Situationen skulle dock kunna förbättras om trådlös kommunikation gjordes tillgänglig för det autonoma fordonet. Istället för att försöka uppfatta omgivningen via kamerasensorer, skulle det autonoma fordonet kunna få den information som behövs via trådlös kommunikation, vilket är vad denna studie behandlade. Studien visade att trådlös kommunikation kommer att ha en betydelse för det autonoma fordonet i framtiden. Slutsatsen grundar sig på att trådlös kommunikation varit en lösning inom andra transportsystem som haft en liknande barriär som för det autonoma fordonet. Man planerar dessutom på att hantera det autonoma fordonets barriär via trådlös kommunikation i pilotprojekt i dagsläget
10
Genin, Terry. "Perception of the visual image". Thesis, University College London (University of London), 1987. http://discovery.ucl.ac.uk/10006547/.
Testo completoAbstract (sommario):
Many scholars tacitly or overtly support the position that the image is becoming the primary means of communication. It is therefore necessary to become visually 'literate' which propensity, it seems, is (unlike 'numeracy' and 'articulacy/literacy') partially innate. During early maturation a complicated set of interactions occur between the physical and psychological aspects of the observer, forming the visually perceptive individual. It is proposed in this thesis that an image comes about as the result of technological, historical, geographic and social forces, an understanding of which, it is suggested, can contextualise the image and aid an understanding of its meaning. Problems seem to occur when fostering visual/spatial understanding through a linguistic medium. Visual/spatial memory is, it seems, capable of being trained, and through that training enhanced. A range of visual image forms can be listed which is shown to be growing while media continue to be developed which can record that range with increasing fidelity. These media appear to be moving towards a standard. This simultaneous growth and containment suggests that a taxonomy of visual images is both possible and educationally desirable. A syllabus is here put forward which consists of an interwoven structure, made up of a database comprising a chronological grouping of image categories, a set of skills and a teaching strategy. The outcomes are evaluated. It was found that the response of the pupils involved could be evaluated in terms of (a) a largely quantitative interpretation of meaning; and (b) a qualitative or critical, idiosyncratic understanding of meaning. It was observed that continuity and sequence were important factors in teaching the syllabus. Test results showed marked positive learning curves when the experimental group was tested against a control group. The a priori claim that si gnificant growth could be shown to occur in a group 's visual understanding of images if the y were sublected to a period of sustained teachin g was substantiated, with the caveat that continuity and sequence needed more attention. A framework for diagnostic evalu- - ation was proposed which recognised the need for evaluating the pupil as critic as well as interpreter.
11
Wiesemann, Elizabeth Y. "The Visual Perception of Elasticity". TopSCHOLAR®, 2008. http://digitalcommons.wku.edu/theses/75.
Testo completo
12
Wardle, Susan G. "Stereopsis in human visual perception". Thesis, The University of Sydney, 2012. https://hdl.handle.net/2123/28933.
Testo completoAbstract (sommario):
The perception of a three-dimensional world is a challenge for the visual
system because the retinal image is only two-dimensional. Stereopsis is
the ability to detect depth from small differences in perspective between
each eye’s two—dimensional view. In this thesis I examine three aspects
of stereoscopic vision in human observers using psychophysical methods.
In part 1, the role of stereopsis in image segmentation and ”camouflage
breaking” is investigated using a contrast masking paradigm. Binocular
disparity is found to reduce contrast masking, and threshold elevation decreases
monotonically with increasing disparity until i8 arcmin of disparity
between the target and a natural image mask. An orientation discrimination
task is used as a control to rule out sensitivity to interocular
decorrelation as an alternative explanation for the effect. The results indicate
that stereopsis facilitates image segmentation as a target can be seen
at a lower contrast when it is in depth defined by disparity. Part 2 examines
the reason for the decline in stereoacuity across the visual field using
equivalent noise analysis. Stereoacuity thresholds are measured in a depth
discrimination task at foveal and peripheral locations (up to 9° eccentricity)
under increasing levels of disparity noise. The equivalent noise model
reveals that internal noise limits peripheral stereoacuity, with no contribution
from a reduction in sampling efficiency. This indicates that a loss
of precision of local disparity estimates early in visual processing limits
peripheral stereoacuity. Part 3 compares speed sensitivity to motion in
depth from two binocular cues: changing disparity over time and interocular
velocity difference. Motion discrimination contours in space-time are
measured for motion-in-depth stimuli of different speeds, containing ei—
ther one or both binocular cue(s). Evidence for speed sensitivity is found
only for slow speeds containing both binocular cues. This suggests that
interocular velocity difference is the critical cue for speed perception of
objects moving in depth. Together, the experimental results are consistent
with the high spatial precision and low temporal resolution of stereoscopic
vision. In the final chapter, the results of the three sections are discussed together
in the context of the role of stereopsis in visual processing. The use
of ’natural’ versus ’artificial’ stimuli in vision research is examined in the
context of the experimental results, and some novel suggestions for future
research in stereopsis are proposed.
13
Wilkie, Sonia. "Auditory manipulation of visual perception". Thesis, View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/39802.
Testo completoAbstract (sommario):
Psychological research on cross-modal auditory-visual perception has focused predominantly on the manipulation of sensory information by visual information. There are relatively few studies of the way auditory stimuli may affect other sensory information. The Sound-induced Illusory Flash is one illusory paradigm that involves the auditory system biasing visual information. However, little is known about this cross-modal illusion. More research is needed into the structure of the illusion that investigates the different conditions under which the Sound induced Illusory Flash manifests and is enhanced or reduced. The research conducted for this thesis investigates the effect of new auditory stimulus variables on the Sound-induced Illusory Flash. The variables to be discussed concern the formation of a contrast in the auditory stimuli, with the contrast creating a rhythm that emphasises the discontinuous nature of the auditory stimuli, and therefore emphasises the illusory percept. The auditory stimulus contrasts include pitch separation with the octave interval, using the frequencies of 261.5 and 523Hz; and spatial separation in the auditory stimuli, presenting the monophonic auditory stimuli binaurally so that individual tones alternate between the left and right channels. I furthered this concept of auditory stimuli separation biasing an illusory percept, by investigating pitch and spatial presentation and localisation of the visual stimuli presentation, when multiple dots were presented. I also conducted analyses to determine if factors other than the auditory stimuli biased the illusory percept. These included the use of non-illusory trials and determining if their inclusion biased the illusory trial percept; and the impact of physical factors such as handedness, eye dominance, corrected vision, and musical experience on the illusory percept. My ultimate aim is to develop the illusory effect as a basis for new intermedia techniques to create the perceptual synchronisation of sound with images. These would be perceived as visually spliced according to the rhythm of the music on the micro time scale.
14
Wilkie, Sonia. "Auditory manipulation of visual perception". View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/39802.
Testo completoAbstract (sommario):
Thesis (M.A. (Hons.))--University of Western Sydney, 2008.Thesis accompanied by CD-ROM with demonstration of possible creative applications. A thesis presented to the University of Western Sydney, College of Arts, MARCS Auditory Laboratories, in fulfilment of the requirements for the degree of Master of Arts (Honours). Includes bibliographies. Thesis minus demonstration CD-ROM also available online at: http://handle.uws.edu.au:8081/1959.7/39849.
15
Tamekue, Cyprien. "Controllability, Visual Illusions and Perception". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST105.
Testo completoAbstract (sommario):
Cette thèse explore deux applications distinctes de la théorie du contrôle dans différents domaines scientifiques : la physique et les neurosciences. La première application se concentre sur la contrôlabilité nulle de l'équation parabolique associée à l'opérateur de Baouendi-Grushin sur la sphère de dimension 2. En revanche, la deuxième application concerne la description mathématique des illusions visuelles du type MacKay, et se focalise sur l'effet MacKay et les expériences psychophysiques de Billock et Tsou, via le contrôle de l'équation des champs neuronaux à une seule couche du type Amari. De plus, pour le besoin d'application à la stabilité entrée-état et la stabilisation robuste, la thèse examine l'existence d'un équilibre dans un modèle de population de champs neuronaux à plusieurs couches de Wilson-Cowan, plus précisément lorsque l'entrée sensorielle est un retour d'état proportionnelle agissant uniquement sur l'état des populations de neurones excitateurs.Dans la première partie, nous étudions les propriétés de contrôlabilité nulle de l'équation parabolique associée à l'opérateur de Baouendi-Grushin défini par la structure presque-riemannienne canonique sur la sphère bidimensionnelle. Cet opérateur présente une dégénérescence à l'équateur de la sphère. Nous fournissons certaines propriétés de contrôlabilité nulle de cette équation dans ce cadre courbé, ce qui généralise celles de l'équation parabolique de Baouendi-Grushin définie sur le plan.Concernant les neurosciences, dans un premier temps, on s'intéresse à la description des illusions visuelles pour lesquelles les outils de la théorie du contrôle et même de l'analyse multiéchelle semblent inappropriés.Dans notre discussion, nous utilisons l'équation des champs neuronaux de type Amari, dans laquelle l'entrée sensorielle est interprétée comme une représentation corticale du stimulus visuel utilisé dans chaque expérience. Elle contient une fonction de contrôle distribuée localisée qui modélise la spécificité du stimulus, par exemple, l'information redondante au centre du motif en entonnoir de MacKay (``rayons de MacKay'') ou le fait que les stimuli visuels dans les expériences de Billock et Tsou sont localisés dans le champ visuel.Toujours dans le cadre des neurosciences, nous étudions l'existence d'un équilibre dans un modèle de population de champs neuronaux à plusieurs couches de Wilson-Cowan lorsque l'entrée sensorielle est un retour d'état proportionnelle agissant uniquement sur l'état du système des populations de neurones excitateurs. Nous proposons une condition suffisante modérée sur les fonctions de réponse garantissant l'existence d'un tel point d'équilibre. L'intérêt de ce travail réside dans son application lors de l'étude de la pertubation des oscillations cérébrales pathologiques associées à la maladie de Parkinson lorsqu'on stimule et mesure uniquement la population de neurones excitateursThis thesis explores two distinct control theory applications in different scientific domains: physics and neuroscience. The first application focuses on the null controllability of the parabolic, spherical Baouendi-Grushin equation. In contrast, the second application involves the mathematical description of the MacKay-type visual illusions, focusing on the MacKay effect and Billock and Tsou's psychophysical experiments by controlling the one-layer Amari-type neural fields equation. Additionally, intending to study input-to-state stability and robust stabilization, the thesis investigates the existence of equilibrium in a multi-layer neural fields population model of Wilson-Cowan, specifically when the sensory input is a proportional feedback acting only on the system's state of the populations of excitatory neurons.In the first part, we investigate the null controllability properties of the parabolic equation associated with the Baouendi-Grushin operator defined by the canonical almost-Riemannian structure on the 2-dimensional sphere. It presents a degeneracy at the equator of the sphere. We provide some null controllability properties of this equation to this curved setting, which generalize that of the parabolic Baouendi-Grushin equation defined on the plane.Regarding neuroscience, initially, the focus lies on the description of visual illusions for which the tools of bifurcation theory and even multiscale analysis appear unsuitable. In our study, we use the neural fields equation of Amari-type in which the sensory input is interpreted as a cortical representation of the visual stimulus used in each experiment. It contains a localised distributed control function that models the stimulus's specificity, e.g., the redundant information in the centre of MacKay's funnel pattern (``MacKay rays'') or the fact that visual stimuli in Billock and Tsou's experiments are localized in the visual field.Always within the framework of neurosciences, we investigate the existence of equilibrium in a multi-layers neural fields population model of Wilson-Cowan when the sensory input is a proportional feedback that acts only on the system's state of the population of excitatory neurons. There, we provide a mild condition on the response functions under which such an equilibrium exists. The interest of this work lies in its application in studying the disruption of pathological brain oscillations associated with Parkinson's disease when stimulating and measuring only the population of excitatory neurons
16
Sanderson, Mariana Welly. "Effects of visual degradation on audio-visual speech perception". Thesis, Birkbeck (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404941.
Testo completoAbstract (sommario):
Audio-visual speech recognition is considered to be a dynamic process that uses auditory and complementary visual speech cues. These are the products of the stream of timed and targeted movements of the articulators in the vocal tract used to produce speech. If the visual aspect of speech is absent or degraded, speech recognition in noise may deteriorate; this was used as a tool to investigate the visual aspect of speech recognition in the following experiments. A series of shadowing and recall experiments assessed the effects of frame rate (temporal) and greyscale level (spatial) variations to the visual aspect of audio-visual presentations of sentences spoken in noisy backgrounds by three, evenly illuminated, speakers. There was a significant decline in shadowing accuracy as the frame rate of presentation fell that was related to the importance of temporal synchrony in audiovisual speech. Shadowing and recall experiments, with recordings from one speaker in two illumination conditions and two greyscale levels, revealed that performance accuracy depended on level of illumination in both tasks, for the audio-visual experimental condition and the audio-alone control condition. Moreover in poor illumination, there was significantly less accurate recall performance at the lower greyscale level. This was related to level of spatial facial information that may be used in speech recognition. Shadowing and recall accuracy of sentence's keywords was related to their degree of visible speech-related movement. Audio-visual shadowing accuracy varied little across the range of movements, but audio-alone shadowing accuracy declined significantly as the degree of movement increased. Visual and auditory target characteristics of words associated with differing audio-visual advantage and degrees of visual movement were determined. The findings were considered in the context of a dynamic model of speech processing, which is dependent on patterns of the timings and targets of the auditory and visual speech signals.
17
Hunt, David Francis. "Perceptions and aversions : does disease avoidance influence tactile and visual perception?" Thesis, University of Bristol, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752740.
Testo completo
18
Hawes, Robin J. "Art and visual perception : what value do contemporary theories of visual perception have for art practice?" Thesis, Cardiff Metropolitan University, 2014. http://hdl.handle.net/10369/6524.
Testo completo
19
Franz, Volker. "The relationship between visually guided motor behavior and visual perception". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961452811.
Testo completo
20
Sun, Li. "Integrated visual perception architecture for robotic clothes perception and manipulation". Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7685/.
Testo completoAbstract (sommario):
This thesis proposes a generic visual perception architecture for robotic clothes perception and manipulation. This proposed architecture is fully integrated with a stereo vision system and a dual-arm robot and is able to perform a number of autonomous laundering tasks. Clothes perception and manipulation is a novel research topic in robotics and has experienced rapid development in recent years. Compared to the task of perceiving and manipulating rigid objects, clothes perception and manipulation poses a greater challenge. This can be attributed to two reasons: firstly, deformable clothing requires precise (high-acuity) visual perception and dexterous manipulation; secondly, as clothing approximates a non-rigid 2-manifold in 3-space, that can adopt a quasi-infinite configuration space, the potential variability in the appearance of clothing items makes them difficult to understand, identify uniquely, and interact with by machine. From an applications perspective, and as part of EU CloPeMa project, the integrated visual perception architecture refines a pre-existing clothing manipulation pipeline by completing pre-wash clothes (category) sorting (using single-shot or interactive perception for garment categorisation and manipulation) and post-wash dual-arm flattening. To the best of the author’s knowledge, as investigated in this thesis, the autonomous clothing perception and manipulation solutions presented here were first proposed and reported by the author. All of the reported robot demonstrations in this work follow a perception-manipulation method- ology where visual and tactile feedback (in the form of surface wrinkledness captured by the high accuracy depth sensor i.e. CloPeMa stereo head or the predictive confidence modelled by Gaussian Processing) serve as the halting criteria in the flattening and sorting tasks, respectively. From scientific perspective, the proposed visual perception architecture addresses the above challenges by parsing and grouping 3D clothing configurations hierarchically from low-level curvatures, through mid-level surface shape representations (providing topological descriptions and 3D texture representations), to high-level semantic structures and statistical descriptions. A range of visual features such as Shape Index, Surface Topologies Analysis and Local Binary Patterns have been adapted within this work to parse clothing surfaces and textures and several novel features have been devised, including B-Spline Patches with Locality-Constrained Linear coding, and Topology Spatial Distance to describe and quantify generic landmarks (wrinkles and folds). The essence of this proposed architecture comprises 3D generic surface parsing and interpretation, which is critical to underpinning a number of laundering tasks and has the potential to be extended to other rigid and non-rigid object perception and manipulation tasks. The experimental results presented in this thesis demonstrate that: firstly, the proposed grasp- ing approach achieves on-average 84.7% accuracy; secondly, the proposed flattening approach is able to flatten towels, t-shirts and pants (shorts) within 9 iterations on-average; thirdly, the proposed clothes recognition pipeline can recognise clothes categories from highly wrinkled configurations and advances the state-of-the-art by 36% in terms of classification accuracy, achieving an 83.2% true-positive classification rate when discriminating between five categories of clothes; finally the Gaussian Process based interactive perception approach exhibits a substantial improvement over single-shot perception. Accordingly, this thesis has advanced the state-of-the-art of robot clothes perception and manipulation.
21
Medwetz, Abigail. "The Effects of Color on Visual Perception and Visual Clutter". Kent State University Honors College / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1556373271322324.
Testo completo
22
Storms, Russell L. "Auditory-visual cross-modal perception phenomena". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA355474.
Testo completoAbstract (sommario):
Dissertation (Ph.D. in Computer Science) Naval Postgraduate School, September 1998.Dissertation supervisor(s): Michael J. Zyda. "September 1998." Includes bibliographical references (p. 207-222). Also Available online.
23
Kosti, Ronak. "Visual scene context in emotion perception". Doctoral thesis, Universitat Oberta de Catalunya, 2019. http://hdl.handle.net/10803/667808.
Testo completoAbstract (sommario):
Els estudis psicològics demostren que el context de l'escena, a més de l'expressió facial i la postura corporal, aporta informació important a la nostra percepció de les emocions de les persones. Tot i això, el processament del context per al reconeixement automàtic de les emocions no s'ha explorat a fons, en part per la manca de dades adequades. En aquesta tesi presentem EMOTIC, un conjunt de dades d'imatges de persones en situacions naturals i diferents anotades amb la seva aparent emoció. La base de dades EMOTIC combina dos tipus de representació d'emocions diferents: (1) un conjunt de 26 categories d'emoció i (2) les dimensions contínues valència, excitació i dominància. També presentem una anàlisi estadística i algorítmica detallada del conjunt de dades juntament amb l'anàlisi d'acords d'anotadors. Els models CNN estan formats per EMOTIC, combinant característiques de la persona amb funcions d'escena (context). Els nostres resultats mostren com el context d'escena aporta informació important per reconèixer automàticament els estats emocionals i motiven més recerca en aquesta direcció.Los estudios psicológicos muestran que el contexto de la escena, además de la expresión facial y la pose corporal, aporta información importante a nuestra percepción de las emociones de las personas. Sin embargo, el procesamiento del contexto para el reconocimiento automático de emociones no se ha explorado en profundidad, en parte debido a la falta de datos adecuados. En esta tesis presentamos EMOTIC, un conjunto de datos de imágenes de personas en situaciones naturales y diferentes anotadas con su aparente emoción. La base de datos EMOTIC combina dos tipos diferentes de representación de emociones: (1) un conjunto de 26 categorías de emociones y (2) las dimensiones continuas de valencia, excitación y dominación. También presentamos un análisis estadístico y algorítmico detallado del conjunto de datos junto con el análisis de concordancia de los anotadores. Los modelos CNN están entrenados en EMOTIC, combinando características de la persona con características de escena (contexto). Nuestros resultados muestran cómo el contexto de la escena aporta información importante para reconocer automáticamente los estados emocionales, lo cual motiva más investigaciones en esta dirección.
Psychological studies show that the context of a setting, in addition to facial expression and body language, lends important information that conditions our perception of people's emotions. However, context's processing in the case of automatic emotion recognition has not been explored in depth, partly due to the lack of sufficient data. In this thesis we present EMOTIC, a dataset of images of people in various natural scenarios annotated with their apparent emotion. The EMOTIC database combines two different types of emotion representation: (1) a set of 26 emotion categories, and (2) the continuous dimensions of valence, arousal and dominance. We also present a detailed statistical and algorithmic analysis of the dataset along with the annotators' agreement analysis. CNN models are trained using EMOTIC, combining a person's features with those of the setting (context). Our results not only show how the context of a setting contributes important information for automatically recognizing emotional states but also promote further research in this direction.
24
Wålarö, Johannes. "Detecting visual plagiarism with perception hashing". Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166771.
Testo completoAbstract (sommario):
Classifying images and deciding algorithmically whether or not they are the same image is a complex problem in com-puter science. This report looks at using perceptual hashing in order to fingerprint images so that they may be matched to one and other. The results shows that threshold match-ing images can be done with good accuracy, while a zero distance match is not reliable in most scenarios. The con-clusion is that a hybrid approach that uses a more inclu-sive perception algorithm to filter out candidates for a more thorough algorithm might be a good choice.
25
Kharbat, Mohd Fawzi. "Robust visual perception for unmanned vehicles". Thesis, Cranfield University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521418.
Testo completo
26
Choi, Changhyun. "Visual object perception in unstructured environments". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53003.
Testo completoAbstract (sommario):
As robotic systems move from well-controlled settings to increasingly unstructured environments, they are required to operate in highly dynamic and cluttered scenarios. Finding an object, estimating its pose, and tracking its pose over time within such scenarios are challenging problems. Although various approaches have been developed to tackle these problems, the scope of objects addressed and the robustness of solutions remain limited. In this thesis, we target a robust object perception using visual sensory information, which spans from the traditional monocular camera to the more recently emerged RGB-D sensor, in unstructured environments. Toward this goal, we address four critical challenges to robust 6-DOF object pose estimation and tracking that current state-of-the-art approaches have, as yet, failed to solve.
The first challenge is how to increase the scope of objects by allowing visual perception to handle both textured and textureless objects. A large number of 3D object models are widely available in online object model databases, and these object models provide significant prior information including geometric shapes and photometric appearances. We note that using both geometric and photometric attributes available from these models enables us to handle both textured and textureless objects. This thesis presents our efforts to broaden the spectrum of objects to be handled by combining geometric and photometric features.
The second challenge is how to dependably estimate and track the pose of an object despite the clutter in backgrounds. Difficulties in object perception rise with the degree of clutter. Background clutter is likely to lead to false measurements, and false measurements tend to result in inaccurate pose estimates. To tackle significant clutter in backgrounds, we present two multiple pose hypotheses frameworks: a particle filtering framework for tracking and a voting framework for pose estimation.
Handling of object discontinuities during tracking, such as severe occlusions, disappearances, and blurring, presents another important challenge. In an ideal scenario, a tracked object is visible throughout the entirety of tracking. However, when an object happens to be occluded by other objects or disappears due to the motions of the object or the camera, difficulties ensue. Because the continuous tracking of an object is critical to robotic manipulation, we propose to devise a method to measure tracking quality and to re-initialize tracking as necessary.
The final challenge we address is performing these tasks within real-time constraints. Our particle filtering and voting frameworks, while time-consuming, are composed of repetitive, simple and independent computations. Inspired by that observation, we propose to run massively parallelized frameworks on a GPU for those robotic perception tasks which must operate within strict time constraints.
27
Buchler, Daniela Martins. "Visual perception of the designed object". Thesis, Staffordshire University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442502.
Testo completoAbstract (sommario):
This investigation deals with the issue of visual perception of the designed object, which is relevant in the context of product differentiation particularly in the case where incremental style changes are made to the external shape design of the product. Such cases present a problem regarding the effectiveness of product differentiation, which this research claims is a matter of visual perception. The problem is that in order for product differentiation to be effective, the design changes must be perceptible. Perceptible differentiation is explained as a function of the physical change, i.e. the Oreal¹ difference, and also of the relevance for the observer of that change, i.e. Operceived¹ difference. This study therefore focuses on the comparison between these two aspects of the designed object: the physical design and the perceived design. Literature from both material culture and the so-called indirect account of perception suggest that visual perception is an interpretation of the artefacts that we see. This visual perception is a function of the physical aspect of that object and of the individual cultural background of the observer. However, it was found that between these two accounts there are theoretical incompatibilities which this study claims could be resolved through scholarly investigation of visual perception of the designed object. The thesis takes these two accounts into consideration and proposes a more comprehensive model of visual perception of the designed object that details and extends the material culture understanding of what constitutes the perceptual experience with the designed object and the role of form in that experience. Theory building was conducted across the disciplines of psychology of perception and design. A revised model was proposed for the area of designed object studies, which was informed by Gregory¹s theoretical framework and incorporated empirical explorations into the model development process. The study therefore contributes knowledge to the research area of design, more specifically to cross-disciplinary methods for theory building on visual perception of the designed object.
28
Delicato, Louise Samantha. "Psychophysical studies of visual motion perception". Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394752.
Testo completo
29
Gonzales, Maria Eunice Quilici. "A cognitive approach to visual perception". Thesis, University of Essex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328824.
Testo completo
30
Corradi, Tadeo. "Integrating visual and tactile robotic perception". Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761005.
Testo completoAbstract (sommario):
The aim of this project is to enable robots to recognise objects and object categories by combining vision and touch. In this thesis, a novel inexpensive tactile sensor design is presented, together with a complete, probabilistic sensor-fusion model. The potential of the model is demonstrated in four areas: (i) Shape Recognition, here the sensor outperforms its most similar rival, (ii) Single-touch Object Recognition, where state-of-the-art results are produced, (iii) Visuo-tactile object recognition, demonstrating the benefits of multi-sensory object representations, and (iv) Object Classification, which has not been reported in the literature to date. Both the sensor design and the novel database were made available. Tactile data collection is performed by a robot. An extensive analysis of data encodings, data processing, and classification methods is presented. The conclusions reached are: (i) the inexpensive tactile sensor can be used for basic shape and object recognition, (ii) object recognition combining vision and touch in a probabilistic manner provides an improvement in accuracy over either modality alone, (iii) when both vision and touch perform poorly independently, the sensor-fusion model proposed provides faster learning, i.e. fewer training samples are required to achieve similar accuracy, and (iv) such a sensor-fusion model is more accurate than either modality alone when attempting to classify unseen objects, as well as when attempting to recognise individual objects from amongst similar other objects of the same class. (v) The preliminary potential is identified for real-life applications: underwater object classification. (vi) The sensor fusion model providesimprovements in classification even for award-winning deep-learning basedcomputer vision models.
31
Bosten, Jenny Marie. "Contrast and constancy in visual perception". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611601.
Testo completo
32
MYERS, KYLE JEAN. "VISUAL PERCEPTION IN CORRELATED NOISE (MODELS)". Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188006.
Testo completoAbstract (sommario):
This dissertation concerns the ability of human observers to perform detection tasks in medical images that contain structured noise. We shall show that physical measures of image quality, such as signal-to-noise ratio (SNR), resolution, modulation transfer function (MTF), and contrast, do not accurately predict how well an observer can detect lesions in an image. We have found that for images with equal pixel SNR, humans can detect a low contrast object more readily in images that have a low-pass noise structure, as opposed to a high-pass noise structure. This finding is important in the comparison of images generated by a classical pinhole imaging system with images generated by a computed tomography imager. We would like to have a figure of merit that accurately predicts a physician's ability to perform perceptual tasks. That is, we want a figure of merit for imaging systems that is more than an evaluation of the physician's performance, measured using human observers and an accepted method such as receiver operating characteristic (ROC) techniques. We want a figure of merit that we can calculate without requiring lengthy observer studies. To perform this calculation, we need a model of the imaging system hardware in cascade with a verified model of the human observer. We have chosen to approach this problem by modelling the human observer as an ideal observer. Our hypothesis is that the human observer acts approximately as an ideal-observer who does not have the ability to prewhiten the noise in an image. Without this ability, the ideal observer's detection performance for even a simple task is degraded substantially in correlated noise. This is just the effect that we have found for human observers. In search of a physiological explanation for a human observer's inability to do prewhitening, we shall investigate the detection capability of the ideal observer when a frequency-selective mechanism is invoked. This mechanism corresponds to the frequency channels known to exist in the human visual system. We shall show that the presence of such a mechanism can explain the degradation of human observer performance in correlated noise.
33
Koh, Hwan Cui. "Visual perception in autism spectrum disorders". Thesis, University of Sheffield, 2009. http://etheses.whiterose.ac.uk/10348/.
Testo completoAbstract (sommario):
This thesis presents research conducted at the cognitive level, the neurophysiological level and the psycho-physical level, for examining vision in ASD. The psycho-physical findings suggest that atypical visual perception in ASD is unlikely to have a sub-cortical origin as sub-cortical magnocellular and parvocellular pathway functioning, and low/high spatial frequency detection in adolescents with ASD were found to be no different from typically-developing controls. There was, however, evidence indicating local motion direction perception deficits in the same adolescents with ASD suggesting that atypical motion perception in ASD may have a cortical origin. Electrophysiological investigation of low level visual perception in ASD revealed findings concurring with this latter interpretation. More specifically, whereas visual evoked potentials demonstrated visuo-integrative processes associated with perception of second order and hyperbolic gratings were not atypical in children with ASD, there was increased activity of the visual cortical region. A further gamma power analysis then demonstrated that there may be increased neuro-connectivity within primary visual area V1 in the children with ASD. Atypical low level visual cortical processes may result in locally-biased perceptual style previously observed in individuals with ASD. However, a cross-cultural comparison of perceptual style in children with ASD and TD children from Singapore and England, found evidence suggesting that locally-biased perceptual style in ASD may not be culturally universal. In sum, lower level visual cortical processes may be atypical in ASD, and whether these atypicalities manifest at the higher perceptual level can be determined by cultural variability in attention and response processes.
34
Shunmugam, Nagarajan. "Operational data extraction using visual perception". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-292216.
Testo completoAbstract (sommario):
The information era has led the manufacturer of trucks and logistics solution providers are inclined towards software as a service (SAAS) based solutions. With advancements in software technologies like artificial intelligence and deep learning, the domain of computer vision has achieved significant performance boosts that it competes with hardware based solutions. Firstly, data is collected from a large number of sensors which can increase production costs and carbon footprint in the environment. Secondly certain useful physical quantities/variables are impossible to measure or turns out to be very expensive solution. So in this dissertation, we are investigating the feasibility of providing the similar solution using a single sensor (dashboard- camera) to measure multiple variables. This provides a sustainable solution even when scaled up in huge fleets. The video frames that can be collected from the visual perception of the truck (i.e. the on-board camera of the truck) is processed by the deep learning techniques and operational data can be extracted. Certain techniques like the image classification and semantic segmentation outputs were experimented and shows potential to replace costly hardware counterparts like Lidar or radar based solutions.Informationstiden har lett till att tillverkare av lastbilar och logistiklösningsleve -rantörer är benägna mot mjukvara som en tjänst (SAAS) baserade lösningar. Med framsteg inom mjukvaruteknik som artificiell intelligens och djupinlärnin har domänen för datorsyn uppnått betydande prestationsförstärkningar att konkurrera med hårdvarubaserade lösningar. För det första samlas data in från ett stort antal sensorer som kan öka produktionskostnaderna och koldioxidavtry -cket i miljön. För det andra är vissa användbara fysiska kvantiteter / variabler omöjliga att mäta eller visar sig vara en mycket dyr lösning. Så i denna avhandling undersöker vi möjligheten att tillhandahålla liknande lösning med hjälp av en enda sensor (instrumentbrädkamera) för att mäta flera variabler. Detta ger en hållbar lösning även när den skalas upp i stora flottor. Videoramar som kan samlas in från truckens visuella uppfattning (dvs. lastbilens inbyggda kamera) bearbetas av djupinlärningsteknikerna och operativa data kan extraher -as. Vissa tekniker som bildklassificering och semantiska segmenteringsutgång -ar experimenterades och visar potential att ersätta dyra hårdvaruprojekt som Lidar eller radarbaserade lösningar.
35
Bayerl, Pierre. "A model of visual motion perception". [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-56293.
Testo completo
36
Fu, Huan. "Robust Dense Prediction for Visual Perception". Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20123.
Testo completoAbstract (sommario):
Dense prediction or pixel-level labeling targets at predicting labels of interest (e.g., categories, depth values, flow vectors, and edge probabilities) for each pixel of an input image. This middle-level computer vision problem plays a crucial role in establishing visual perception systems for the future intelligent world. Therefore, tremendous efforts have been made in the past decades to explore the solution for robust dense prediction, and recent studies have continuously obtained significant progress relying on deep Fully Convolutional Networks (FCNs). According to the expected label, dense prediction contains a set of subtasks. Building robust models for each task must examine the particular property, but the main intuition and motivation for the network architecture development are shared across different tasks. In the thesis, we take the well-known problems of scene parsing, monocular depth estimation, and edge detection as examples, and devise some advanced and highly extensible techniques by addressing both the individual and collective issues for robust dense prediction. Specific to scene parsing, employing hierarchical convolutional features is essential to obtain high-resolution and fine-grained predictions. Previous algorithms regularly aggregate them via concatenation or linear combination, which cannot sufficiently exploit the diversities of the contextual information and the spatial inhomogeneity of a scene. We propose some novel attention mechanisms, i.e., adaptive hierarchical feature aggregation (AHFA) and mixture-of-experts (MoE), to re-weight different levels of features at each spatial location according to the local structure and surrounding contextual information before aggregation. Existing works on depth estimation often overlook the strong inherent ordinal correlation of depth values resulting in inferior performance. Motivated by the observation, we introduce the ranking mechanism for depth estimation by proposing an effective ordinal regression constraint. For edge detection, common approaches simply predict the boundary probability for each pixel individually from the receptive fields where the pixel is centered at. Differently, we propose that modeling the boundary structures or position sensitive scores are more flexible because of the implied feature competition for the prediction of each spatial position. We also study unsupervised domain mapping which is of general applicability, enabling a consolidated solution for dense prediction. Advanced unsupervised domain mapping approaches mainly rely on Generative Adversarial Networks (GANs) to make the prediction indistinguishable from reality (e.g., generated pseudo parsing vs. truth parsing), and reduce the solution space with high-level constraints and assumptions to guarantee that an input and the corresponding output are paired up in a meaningful way in the absence of unmatched training samples. However, they overlook the special property of images that simple geometric transformations do not change the semantics of an image. With that motivation, we propose to enforce geometry consistency as a constraint and demonstrate that it can largely eliminate unreasonable mappings and produce more reliable solutions.
37
Serrano, Jose Gaston. "Visual perception of simulated conducting motions". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186593.
Testo completoAbstract (sommario):
The purpose of this investigation was to examine subject response to music conducting motions simulated on a computer screen. Forty musicians and forty non-musicians responded to a point of light moving around a computer screen simulating the tip of a conductor's baton. Subjects were asked to press a button every time they perceived a beat portrayed in the motions. The timing of subject responses to four modes of motion was recorded and analyzed. In order to produce sound from their musical instruments, musicians must undergo a process that involves developing a mental image of the upcoming sound, creating an action program, and performing the chain of physical events that will culminate in the production of the desired sound. Even though it may last a mere fraction of a second, this process of anticipation is an essential component of music making. Whereas solo musicians anticipate the music rather freely, ensemble musicians must meet an essential requirement for obtaining satisfying musical results: they must play together. Since they also need to anticipate the music, then they must anticipate together in order to play together. This coordination is accomplished by way of visual information provided by the conductor. In the present study it was hypothesized that speed and direction of conducting motions from any given beat to the next play an important role in the observers' ability to anticipate and synchronize their motor activity. The experimental design allowed the author to examine visual perception of simulated conducting motions showing distinct motion behaviors, in isolation from actual sound and other sensory cues. Results of this investigation indicate that both musicians and non-musicians respond with a high degree of uniformity to a type of conducting motion which resembles the motion produced by gravitational forces--accelerating going down, decelerating going up, following a parabolic trajectory when moving to either side. On the other hand, a motion which is inversely proportional to the motion produced by gravity yielded mixed results: non-musicians responded more uniformly than did musicians, as the latter were divided according to two distinct interpretations of where the beats occurred within the simulated conducting patterns.
38
Zamboni, Elisa. "Biases in perception of visual motion". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43287/.
Testo completoAbstract (sommario):
Perceptual decision making refers to the process of making a choice among a series of options based on sensory information. Several studies have used visual stimuli to gain an understanding of the processes involved in encoding sensory information and its decoding, leading to a perceptual decision. One popular visual modality for studying these questions is motion and the ability to discriminate between axes of motion. Several mathematical models describing the processes of perceptual decision making have been proposed – many of them are based on data from electrophysiological experiments on macaque monkeys. By directly recording neuronal activity while monkeys were presented with different visual stimuli and making categorical choices about the perceived direction of motion, scientists have been able to study how decisions are made when enough perceptual evidence is accumulated to reach a threshold. A particularly interesting aspect of perceptual decision making is that it allows the study of situations in which the choice deviates from the physical features characterising the stimulus (e.g., a leftward motion is presented but the subject reports perceiving a rightward motion). A type of such perceptual bias is called reference repulsion: a systematic bias away from a reference when estimating the direction of motion of a stimulus. Several possible explanations of this phenomenon have been proposed: incorrect encoding of sensory information, influence of prior knowledge about the world, response-related factors such as expectations, rewards, and response history. The aim of this thesis was to shed light on when in the sequence of decision making such perceptual biases arise, as well as further address both sensory and higher-order factors that influence perceptual decisions of visual stimuli. We combined a series of psychophysical, eye-tracking, and neuroimaging studies, together with computational modelling approaches, to selectively look at the effect of: sensory information available during decision making, task-related sensory information processing, response modality, and also look for specific mechanisms involved in processing highly similar/dissimilar stimuli. The findings presented in this thesis show that perceptual biases in estimates of motion direction arise at a later stage than at the encoding of sensory representation, as previously thought. In particular, we show that information present at the time of the response is fundamental for the bias to emerge: the presence of a reference while estimating direction of motion results in reference repulsion, but this effect is not there when the same estimate is given in the absence of a reference. Moreover, the information given by the reference at the time of response – when subjects report the perceived motion, rather than at the time of stimulus presentation – plays a crucial role in the observed perceptual bias. These findings were used to develop a mathematical model able to describe the phenomena observed, as well as making a series of testable predictions. For example, the model could be used in future work to predict responses when more than one reference is present, when order of presentation of target and reference is inverted, and so on. By manipulating the modality with which subjects estimated the direction of motion of the stimuli they were presented with, it was also possible to show that a perceptual bias is observed for manual reproduction of the perceived direction, but not when the response is given by a saccadic eye movement. Finally, by looking at the brain activity recorded when performing a coarse / fine discrimination task in a functional magnetic resonance imaging (fMRI) study, we aimed at distinguishing between activity patterns encoding highly dissimilar / similar stimuli. For these analyses, we used both conventional, univariate analysis techniques, as well as a more advanced and relatively more recent multivariate approaches to the data. First, the retinotopic mapping of areas in early visual cortex and area MT was obtained through phase-encoded methods. Second, a version of the Generalised Linear Model was applied to the data measured while subjects were performing a fine / coarse discrimination task. This allowed to ensure the adequacy of tasks and stimuli used in the imaging study. I also applied the population Receptive Field methodology to fit a more explicit, physiologically relevant model of visual responses to the voxel-wise fMRI time series. Third, given that the spatial scale of the question we addressed in this study required aggregating sub-voxel differences in the fMRI responses during a fine versus coarse visual motion discrimination task, we employed a multivariate approach. This consisted in implementing a forward encoding model aimed at reducing the number of dimensions from several hundreds (given by the number of voxels) to a much smaller set of hypothetical channels. By considering the responses in these channels as a weighted combination from many hundred voxels we re-cast the activity patterns in a physiologically relevant space to predict responses to arbitrary visual motion directions. While there were very interesting aspects to the results from these imaging experiments, the analysis was inconclusive on any task-related shifts in stimulus encoding. Possible explanations, together with alternative paradigms that can be used in future to further address this question are discussed.
39
Nguyen, Duc Minh Chau. "Affordance learning for visual-semantic perception". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2443.
Testo completoAbstract (sommario):
Affordance Learning is linked to the study of interactions between robots and objects, including how robots perceive objects by scene understanding. This area has been popular in the Psychology, which has recently come to influence Computer Vision. In this way, Computer Vision has borrowed the concept of affordance from Psychology in order to develop Visual-Semantic recognition systems, and to develop the capabilities of robots to interact with objects, in particular. However, existing systems of Affordance Learning are still limited to detecting and segmenting object affordances, which is called Affordance Segmentation. Further, these systems are not designed to develop specific abilities to reason about affordances. For example, a Visual-Semantic system, for captioning a scene, can extract information from an image, such as “a person holds a chocolate bar and eats it”, but does not highlight the affordances: “hold” and “eat”. Indeed, these affordances and others commonly appear within all aspects of life, since affordances usually connect to actions (from a linguistic view, affordances are generally known as verbs in sentences). Due to the above mentioned limitations, this thesis aims to develop systems of Affordance Learning for Visual-Semantic Perception. These systems can be built using Deep Learning, which has been empirically shown to be efficient for performing Computer Vision tasks.
There are two goals of the thesis: (1) study what are the key factors that contribute to the performance of Affordance Segmentation and (2) reason about affordances (Affordance Reasoning) based on parts of objects for Visual-Semantic Perception. In terms of the first goal, the thesis mainly investigates the feature extraction module as this is one of the earliest steps in learning to segment affordances.
The thesis finds that the quality of feature extraction from images plays a vital role in improved performance of Affordance Segmentation. With regard to the second goal, the thesis infers affordances from object parts to reason about part-affordance relationships. Based on this approach, the thesis devises an Object Affordance Reasoning Network that can learn to construct relationships between affordances and object parts. As a result, reasoning about affordance becomes achievable in the generation of scene graphs of affordances and object parts. Empirical results, obtained from extensive experiments, show the potential of the system (that the thesis developed) towards Affordance Reasoning from Scene Graph Generation.
40
Boyle, Justin Robert. "Improving Perception From Electronic Visual Prostheses". Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16106/1/Justin_Boyle_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis explores methods for enhancing digital image-like sensations which might be similar to those experienced by blind users of electronic visual prostheses. Visual prostheses, otherwise referred to as artificial vision systems or bionic eyes, may operate at ultra low image quality and information levels as opposed to more common electronic displays such as televisions, for which our expectations of image quality are much higher. The scope of the research is limited to enhancement by digital image processing: that is, by manipulating the content of images presented to the user. The work was undertaken to improve the effectiveness of visual prostheses in representing the visible world.
Presently visual prosthesis development is limited to animal models in Australia and prototype human trials overseas. Consequently this thesis deals with simulated vision experiments using normally sighted viewers. The experiments involve an original application of existing image processing techniques to the field of low quality vision anticipated from visual prostheses.
Resulting from this work are firstly recommendations for effective image processing methods for enhancing viewer perception when using visual prosthesis prototypes. Although limited to low quality images, recognition of some objects can still be achieved, and it is useful for a viewer to be presented with several variations of the image representing different processing methods. Scene understanding can be improved by incorporating Region-of-Interest techniques that identify salient areas within images and allow a user to zoom into that area of the image. Also there is some benefit in tailoring the image processing depending on the type of scene.
Secondly the research involved the construction of a metric for basic information required for the interpretation of a visual scene at low image quality. The amount of information content within an image was quantified using inherent attributes of the image and shown to be positively correlated with the ability of the image to be recognised at low quality.
41
Boyle, Justin Robert. "Improving Perception From Electronic Visual Prostheses". Queensland University of Technology, 2005. http://eprints.qut.edu.au/16106/.
Testo completoAbstract (sommario):
This thesis explores methods for enhancing digital image-like sensations which might be similar to those experienced by blind users of electronic visual prostheses. Visual prostheses, otherwise referred to as artificial vision systems or bionic eyes, may operate at ultra low image quality and information levels as opposed to more common electronic displays such as televisions, for which our expectations of image quality are much higher. The scope of the research is limited to enhancement by digital image processing: that is, by manipulating the content of images presented to the user. The work was undertaken to improve the effectiveness of visual prostheses in representing the visible world. Presently visual prosthesis development is limited to animal models in Australia and prototype human trials overseas. Consequently this thesis deals with simulated vision experiments using normally sighted viewers. The experiments involve an original application of existing image processing techniques to the field of low quality vision anticipated from visual prostheses. Resulting from this work are firstly recommendations for effective image processing methods for enhancing viewer perception when using visual prosthesis prototypes. Although limited to low quality images, recognition of some objects can still be achieved, and it is useful for a viewer to be presented with several variations of the image representing different processing methods. Scene understanding can be improved by incorporating Region-of-Interest techniques that identify salient areas within images and allow a user to zoom into that area of the image. Also there is some benefit in tailoring the image processing depending on the type of scene. Secondly the research involved the construction of a metric for basic information required for the interpretation of a visual scene at low image quality. The amount of information content within an image was quantified using inherent attributes of the image and shown to be positively correlated with the ability of the image to be recognised at low quality.
42
Kanizsar, Orsolya. "Visual Cognition In Dogs. Motion Perception". Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3421837.
Testo completoAbstract (sommario):
In the last decades several studies have been investigated the behavior and cognition of dogs (Canis familiars) especially from socio-cognitive aspects. We already gained a solid knowledge on how dogs communicate with humans and conspecific partners, how they are able recognize, interpret and rely on social-communicational cues in their everyday lives, thus continuously perceiving a flow of visual information. However, the fundaments of how they process these visual information are still missing from the literature. The current PhD project have been developed around three independent studies, all of them investigating visual cognition in dogs (and for one case, also in humans) in the domain of perceiving motion.Negli ultimi decenni sono stati studiati diversi studi sul comportamento e sulla cognizione dei cani (familiari di Canis), specialmente da aspetti socio-cognitivi. Abbiamo già acquisito una solida conoscenza su come i cani comunicano con gli umani e con i partner conspecifici, come sono in grado di riconoscere, interpretare e fare affidamento su segnali di comunicazione sociale nella loro vita quotidiana, percependo continuamente un flusso di informazioni visive. Tuttavia, i fondamenti di come elaborano queste informazioni visive sono ancora mancanti dalla letteratura. L'attuale progetto di dottorato è stato sviluppato intorno a tre studi indipendenti, tutti studiati sulla cognizione visiva nei cani (e per un caso, anche negli esseri umani) nel campo del percepire il movimento.
43
Ngo, Mary Kim. "Facilitating visual target identification using non-visual cues". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:6e05bfc4-f049-43a3-8ecc-4db38f8cbb09.
Testo completoAbstract (sommario):
The research presented in this thesis was designed to investigate whether and how the temporal synchrony and spatial congruence of non-visual cues with visual targets could work together to improve the discrimination and identification of visual targets in neurologically-healthy adult humans. The speed and accuracy of participants’ responses were compared following the presence or absence of temporally synchronous and/or spatially congruent or incongruent auditory, vibrotactile, and audiotactile cues in the context of dynamic visual search and rapidly-masked visual target identification. The understanding of the effects of auditory, vibrotactile, and audiotactile cues derived from these laboratory-based tasks was then applied to an air traffic control simulation involving the detection and resolution of potential conflicts (represented as visual targets amidst dynamic and cluttered visual stimuli). The results of the experiments reported in this thesis demonstrate that, in the laboratory-based setting, temporally synchronous and spatially informative non-visual cues both gave rise to significant improvements in participants’ performance, and the combination of temporal and spatial cuing gave rise to additional improvements in visual target identification performance. In the real-world setting, however, only the temporally synchronous unimodal auditory and bimodal audiotactile cues gave rise to a consistent facilitation of participants’ visual target detection performance. The mechanisms and accounts proposed to explain the effects of spatial and temporal cuing, namely multisensory integration and attention, are examined and discussed with respect to the observed improvements in participants’ visual target identification performance.
44
Hu, Gang. "Effect of visual and non-visual cues in the generation of reorientation illusions". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0020/MQ56182.pdf.
Testo completo
45
Becker, Mark W. "Volatile visual representations : the information represented while viewing visual scenes /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9992379.
Testo completo
46
Marini, Ludovica Orsola Adriana. "Perception and representation in the visual brain and in visual art". Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428716.
Testo completo
47
de, Haas B. "Contextual modulations of visual perception and visual cortex activity in humans". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1435556/.
Testo completoAbstract (sommario):
Visual perception and neural processing depend on more than retinal stimulation alone. They are modulated by contextual factors like cross-modal input, the current focus of attention or previous experience. In this thesis I investigate ways in which these factors affect vision. A first series of experiments investigates how co-occurring sounds modulate vision, with an emphasis on temporal aspects of visual processing. In three behavioral experiments I find that participants are unable to ignore the duration of co-occurring sounds when giving visual duration judgments. Furthermore, prolonged sound duration goes along with improved detection sensitivity for visual stimuli and thus extends beyond duration judgments per se. I go on to test a cross-modal illusion in which the perceived number of flashes in a rapid series is affected by the number of co-occurring beeps (the sound-Induced flash illusion). Combining data from structural magnetic resonance imaging (MRI) and a behavioral experiment I find that individual proneness to this illusion is linked with less grey matter volume in early visual cortex. Finally, I test how co-occurring sounds affect the cortical representation of more natural visual stimuli. A functional MRI (fMRI) experiment investigates patterns of activation evoked by short video clips in visual areas V1-3. The trial-by-trial reliability of such patterns is reduced for videos accompanied by mismatching sounds. Turning from cross-modal effects to more intrinsic sources of contextual modulation I test how attention affects visual representations in V1-3. Using fMRI and population receptive field (pRF) mapping I find that high perceptual load at fixation renders spatial tuning for the surrounding visual field coarser and goes along with pRFs being radially repelled. In a final behavioral and fMRI experiment I find that the perception of face features is modulated by retinal stimulus location. Eye and mouth stimuli are recognized better, and evoke more discriminable patterns of activation in face sensitive patches of cortex, when they are presented at canonical locations. Taken together, these experiments underscore the importance of contextual modulation for vision, reveal some previously unknown such factors and point to possible neural mechanisms underlying them. Finally, they argue for an understanding of vision as a process using all available cues to arrive at optimal estimates for the causes of sensory events.
48
Likens, Aaron D. "Hysteresis in visual search /". Read thesis online, 2010. http://library.uco.edu/UCOthesis/LikensAD2010.pdf.
Testo completo
49
Griffiths, Shaaron S., e shaaron griffiths@deakin edu au. "Spatial and temporal disparaties in aurally aided visual search". Deakin University. School of Psychology, 2001. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20061207.134032.
Testo completoAbstract (sommario):
Research over the last decade has shown that auditorily cuing the location of visual targets reduces the time taken to locate and identify targets for both free-field and virtually presented sounds. The first study conducted for this thesis confirmed these findings over an extensive region of free-field space. However, the number of sound locations that are measured and stored in the data library of most 3-D audio spatial systems is limited, so that there is often a discrepancy in position between the cued and physical location of the target. Sampling limitations in the systems also produce temporal delays in which the stored data can be conveyed to operators. To investigate the effects of spatial and temporal disparities in audio cuing of visual search, and to provide evidence to alleviate concerns that psychological research lags behind the capabilities to design and implement synthetic interfaces, experiments were conducted to examine (a) the magnitude of spatial separation, and (b) the duration of temporal delay that intervened between auditory spatial cues and visual targets to alter response times to locate targets and discriminate their shape, relative to when the stimuli were spatially aligned, and temporally synchronised, respectively. Participants listened to free-field sound localisation cues that were presented with a single, highly visible target that could appear anywhere across 360° of azimuthal space on the vertical mid-line (spatial separation), or extended to 45° above and below the vertical mid-line (temporal delay). A vertical or horizontal spatial separation of 40° between the stimuli significantly increased response times, while separations of 30° or less did not reach significance. Response times were slowed at most target locations when auditory cues occurred 770 msecs prior to the appearance of targets, but not with similar durations of temporal delay (i.e., 440 msecs or less). When sounds followed the appearance of targets, the stimulus onset asynchrony that affected response times was dependent on target location, and ranged from 440 msecs at higher elevations and rearward of participants, to 1,100 msecs on the vertical mid-line. If targets appeared in the frontal field of view, no delay of acoustical stimulation affected performance. Finally, when conditions of spatial separation and temporal delay were combined, visual search times were degraded with a shorter stimulus onset asynchrony than when only the temporal relationship between the stimuli was varied, but responses to spatial separation were unaffected. The implications of the results for the development of synthetic audio spatial systems to aid visual search tasks was discussed.
50
Kim, Sujin. "Serial dependence in higher-level visual processing". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25395.
Testo completoAbstract (sommario):
Visual perception is not always veridical from moment to moment and can be biased by the recent history of visual input: a phenomenon called serial dependence. In this thesis, I present three studies that add to the further understanding of serial dependence, particularly in relation to higher-level visual processing. Study 1 tested whether aesthetic judgments of various artworks are subject to serial dependence. The task was to rate the attractiveness of serially presented paintings. The results indicate that attractiveness ratings of artworks are positively biased toward the recent past. In Study 2, the mechanism of serial dependence was investigated by dissociating low and higher stages of visual processing using binocular rivalry. In the experiment, two orthogonal gratings were briefly presented in a rivalry trial, followed by a monocular test grating. The results showed that the perceptually dominant grating, but not the suppressed one, exerted an attractive orientation bias on the test grating. Study 3, using face attractiveness ratings and identification as tasks, investigated whether the mechanism of serial dependence established with a low-level visual task would generalise to higher-level visual processing. Sensory uncertainty was manipulated on a trial-by-trial basis by overlaying various levels of random noise masks onto the face stimuli. The results indicated that bias magnitude toward the past was modulated by both previous and current sensory uncertainty, given that the noise modulation was appropriate. In summary, these empirical findings suggest that: i) serial dependence occurs for a task that requires a higher-level visual evaluation of a complex stimulus, ii) priors on which serial dependence is based are updated at a post-perceptual stage of visual processing, and iii) the underlying mechanism of serial dependence generalises across multiple visual stages.