Littérature scientifique sur le sujet « Social stimili »

Using a Pavlovian procedure, human subjects were conditioned to pictures of angry faces with a mild electric shock as the unconditioned stimulus. They were then tested with backward masking conditions preventing conscious recognition of the facial stimuli. In the first experiment a shock followed a particular nonmasked angry face which was exposed among many other faces. Although the subjects did not rate this face as familiar in a subsequent test when is was presented masked among other masked and nonmasked faces, it elicited larger skin conductance responses than did nonshocked control faces. This dissociation between explicit recognition and implicit skin conductance differentiation was replicated in the second experiment, in which the subjects rated their shock expectancy. Although conditioning resulted in much better differentiation between conditioned and control faces during nonmasked than masked test-trials, skin conductance differentiation did not differ between the two masking conditions.

Although the presence of social-support figures (e.g., close friends and family members) is known to increase feelings of safety, reduce threat responses, and improve health, the route by which these effects occur is not well understood. One explanation is that social-support figures are members of a powerful category of safety signals—prepared safety stimuli. Here, we review research demonstrating that social-support figures act as prepared safety stimuli and explore the impact that these unique safety stimuli have on fear-learning processes. According to recent work, the presence of social-support figures both reduces fear acquisition and enhances fear extinction, ultimately decreasing perceptions of threat. These findings shed light on the route by which social support buffers against threat and illustrate the unique properties of prepared safety stimuli and how they might be used to improve mental and physical health outcomes.

Abstract Background Placebo analgesia can be induced by social observational learning. The aim of this study was to determine whether this effect can be influenced by the social status of a model. Methods Healthy volunteers were randomly assigned to three groups: a group that observed a video featuring a high-status model (introduced as a professor), a group that observed a video featuring a low-status model (introduced as a janitor), and a control group. Participants observed videos showing a model (of high or low status) undergoing the experimental procedure, during which he received pain stimuli. In each group, half of participants watched a video in which the model rated blue stimuli as more painful (6–8 on the numeric rating scale) and orange stimuli as less painful (1–3 on the numeric rating scale), whereas the other half of participants watched a video in which the model rated orange stimuli as more painful and blue stimuli as less painful. Participants in the control group did not watch any video. Then, all participants received 16 electrocutaneous pain stimuli of the same intensity, preceded by either blue or orange colors. The perceived social status of the model and the trait empathy of participants were measured. Results Placebo analgesia was induced in both experimental groups, yet no difference in the magnitude of the effect was found. However, we found that the participants’ individual ratings of the model’s social status predicted the magnitude of placebo analgesia. Conclusion This is the first study to show that the perception of a model’s social status is related to the magnitude of placebo analgesia induced by observational learning.

Qualia, the individual instances of subjective conscious experience, are private events. However, in everyday life, we assume qualia of others and their perceptual worlds, to be similar to ours. One way this similarity is possible is if qualia of others somehow contribute to the production of qualia by our own brain and vice versa. To test this hypothesis, we focused on the mean voltages of event-related brain potentials (ERPs) in the time-window of the P600 component, whose amplitude correlates positively with conscious awareness. These ERPs were elicited by stimuli of the international affective picture system in 16 pairs of friends, siblings or couples going side by side through hyperscanning without having to interact. Each member of each pair faced one half of the screen and could not see what the other member was presented with on the other half. One stimulus occurred on each half simultaneously. The sameness of these two stimuli was manipulated as well as the participants’ belief in that sameness. ERPs were more negative over left frontal sites and P600 amplitudes were minimal at midline sites when the two stimuli were, and were believed to be, different, suggesting that this belief could filter others’ qualia. ERPs were less negative over left frontal sites and midline P600s were a bit larger when the two stimuli were, and were believed to be, the same, suggesting some mutual enrichment of the content of awareness in conditions of real and assumed similarity. When stimuli were believed to be the same but actually differed, P600s were greater over a large number of sites, suggesting greater enrichment in conditions of qualia difference and assumed similarity. P600s were also larger over many sites, when stimuli were believed to differ but were identical, suggesting that qualia similar to ours could pass the “believed-different filter”.

Secondo il filosofo greco Aristotele "L'uomo è per natura un animale sociale". Dopo 2350 anni, oggi sappiamo che questa affermazione è solo parzialmente vera. Sebbene le evidenze sperimentali abbiano messo in luce una preferenza per gli stimoli e le interazioni sociali negli esseri umani, questa conclusione non sembra applicabile a tutti gli individui e contesti. L'elaborazione degli stimoli sociali può infatti essere influenzata da caratteristiche degli stimoli sociali e non sociali, presentati in competizione, nonché da caratteristiche inter-individuali. Tra quest'ultime, il Disturbo dello Spettro Autistico è sicuramente un esempio prototipico di atipicità nei comportamenti sociali e nella cognizione sociale. Il presente lavoro di tesi era rivolta a: i. indagare se gli stimoli sociali esercitano una priorità di elaborazione negli individui a sviluppo tipico (TD), anche quando presentati in competizione con altri stimoli non sociali fortemente rilevanti (denaro); ii. Indagare se e come gli individui con ASD rispondono a stimoli sociali vs non sociali rispetto agli individui TD, prendendo in esame un duplice livello di elaborazione, cognitivo e fisiologico; iii. Indagare se le differenze tra individui TD e ASD nell'elaborazione degli stimoli sociali e non sociali possano considerarsi l'espressione di un fenotipo familiare allargato; iv. Indagare la possibilità di modificare la salienza degli stimoli sociali negli individui con ASD attraverso una metodologia di apprendimento implicito ABMT (Attention Bias Modification Treatment). La presente tesi presenta tre implicazioni: teorica, metodologica e clinica. Per quanto riguarda le implicazioni teoriche, il presente lavoro supporta solo parzialmente l'affermazione di Aristotele. I risultati infatti hanno evidenziato chiaramente che, sebbene gli stimoli sociali abbiano solitamente un accesso prioritario agli step di elaborazione, la loro valenza può essere influenzata da una varietà di variabili come le differenze individuali (e.g., tratti autistici) o caratteristiche degli stimoli non sociali presentati in competizione quelli sociali (e.g., stimoli di alto interesse autistico per l'autismo). Altresì, i risultati sottolineano la necessità di considerare le diverse fasi dell'elaborazione dello stimolo (cognitivo vs fisiologico) nell'esame delle risposte cognitive e fisologiche a diverse tipologie di stimoli. Per quanto riguarda le implicazioni metodologiche, il presente lavoro suggerisce l'integrazione di tecniche tradizionali con tecniche computazionali più avanzate (es: Machine Learning o Deep Learning). Per quanto riguarda le implicazioni cliniche, questo lavoro ha fornito un esame circa le modalità di elaborazione degli stimoli sociali in bambini e adulti ASD, sia a livello attentivo che fisiologico. In secondo luogo, ha contribuito a far ulteriormente luce sul concetto di fenotipo autistico allargato, mostrando i limiti di questo concetto e l'ipotetico ruolo di variabili ambientali nel modulare il comportamento sociale nell'autismo.
According to the Greek philosopher Aristotle “Man is by nature a social animal”. After 2350 years, we know that this statement is partially true. Although experimental evidence has reported a preference for social stimuli and social interactions in human beings, this conclusion does not apply to every individuals and contexts. Social stimuli processing can indeed be affected by stimuli and competitive non-social stimuli features as well as by inter-individual characteristics. Among the clinical conditions characterized by atypicality in social behaviours and social cognition (e.g., schizophrenia, personality disorders etc.), Autism Spectrum Disorder (ASD) is the most prototypical example. The present dissertation was aimed at: i. investigating whether social stimuli are prioritized by typically developed individuals (TD) even when they attentively compete with other relevant non-social stimuli (money); ii. Investigating whether and how individuals with ASD differently respond to social vs non-social stimuli compared to TD individuals, by considering both a cognitive and a physiological level of processing; iii. Investigating whether the differences between TD and ASD individuals in social vs nonsocial stimuli processing are the expression of a familiar phenotype; iv. Investigating whether it is possible to modify the salience of social stimuli in ASD individuals through an Attention Bias Modification Treatment (ABMT) methodology. The present dissertation is expected to provide three main implications: theoretical, methodological and clinical. As concerns the theoretical implications, the present work only partially supports Aristotle statement mentioned in the introduction. Indeed, the reported findings have clearly highlighted that, although social stimuli are usually prioritized, their valence may be affected by a variety of variables such as individual differences (e.g., autistic traits) or characteristics of the non-social stimuli presented in competition with the social ones (e.g., High Autism Interest stimuli). Finally, results stress the importance of considering the different stages of stimulus processing (i.e., cognitive vs physiological) when examining human responses to social vs non-social stimuli. As regards the methodological implications, the present work provides important hints for future research on social vs non-social stimuli processing with TD and atypical development populations, by suggesting the integration of traditional techniques with more advanced computational techniques (i.e., Machine Learning). As concern the clinical implications, this work has provided a rich examination of how children and adults of ASD children process social and non-social stimuli both at an attentional level and at a physiological level. Secondly, it has contributed to further shedding light on the concept of BAP, by showing its limitations and the role played by environmental variables in shaping the parents of ASD children’s behavioral responses.

Los trastornos de ansiedad constituyen un reto para la psiquiatría y la psicología clínica. Cerca de un 30% de la población sufre, o ha sufrido, uno o más trastornos de ansiedad a lo largo de su vida, siendo dicho grupo de trastornos el más frecuente dentro del DSM-IV. Las aproximaciones teóricas basadas en los modelos de aprendizaje aversivo han ocupado un lugar muy importante entre los modelos etiológicos de dichos trastornos. A pesar de que el condicionamiento del miedo es un proceso adaptativo y de gran importancia para la supervivencia, puede acabar convirtiéndose en clínicamente relevante cuando la reactividad al Estímulo Condicionado (EC) persiste en ausencia de contingencia entre el EC y el Estímulo Incondicionado (EI). Mediante procesos de condicionamiento clásico aversivo pueda aparecer un trastorno de ansiedad durante o después de un acontecimiento traumático o en un período de estrés significativo. Sin embargo, no todas las personas expuestas a este tipo de sucesos acaban desarrollando un trastorno. Algunos estudios han demostrado un mayor condicionamiento y una mayor resistencia a la extinción en pacientes ansiosos comparados con controles sanos sugiriendo que pacientes con trastornos de ansiedad se caracterizan por una elevada condicionabilidad y que ésta es una de las razones por las que, en situaciones de exposición a incidentes aversivos, sólo algunos individuos desarrollan miedos patológicos, mientras que otros muestran una respuesta adaptativa de miedo. La mayoría de estudios han utilizado el reflejo de sobresalto como índice de procesamiento afectivo. Consiste en una respuesta defensiva súbita que presentan muchas especies animales ante un estímulo intenso e inesperado. En humanos, puede ser medido de forma bastante sencilla registrando la respuesta electromiográfica en el músculo orbicularis oculi. El incremento del reflejo de sobresalto cuando un individuo está experimentando un estado de miedo o ansiedad se denomina reflejo de sobresalto potenciado por miedo. Durante los últimos años, éste se ha convertido en una herramienta de gran utilidad para la investigación traslacional de los trastornos de ansiedad. La mayor parte de los trabajos han utilizado estímulos evolutivamente poco “preparados” y algunos no han demostrado mayor condicionabilidad en pacientes con trastornos de ansiedad. Esto nos alerta de la necesidad de emplear paradigmas que contemplen estímulos incondicionados más relevantes para el trastorno objeto de estudio. Por tanto, el objetivo general del presente proyecto fue investigar el papel del condicionamiento aversivo de estímulos socialmente relevantes como factor específico de vulnerabilidad a la fobia social, utilizando el reflejo de sobresalto en pacientes con fobia social respecto a pacientes con trastorno de pánico con agorafobia y controles sanos. Para llevarlo a cabo, se empleó un paradigma de condicionamiento diferencial desarrollado por Lissek et al. (2008) en el que imágenes de personas con una expresión facial neutra (EC) se aparearon con tres tipos de estímulos visuales/auditivos: insultos y expresiones faciales de crítica (EIneg); comentarios y expresiones faciales neutras (EIneu); y cumplidos y expresiones faciales positivas (EIpos). Los resultados del presente trabajo no demostraron una mayor condicionabilidad en pacientes con fobia social respecto a pacientes con trastorno de pánico con agorafobia y controles sanos. Es posible que otros procesos tanto asociativos (por ejemplo, extinción del miedo) como no asociativos (por ejemplo, procesos cognitivos y atencionales) tengan un papel más importante en la fobia social que un mayor condicionamiento.
Anxiety disorders represent a challenge for psychiatry and clinical psychology. Near 30 % of the population suffers, or has suffered, one or more anxiety disorder along his life, being this disorder the most frequent group of them inside the DSM-IV. The theoretical approximations based on aversive learning models have occupied traditionally a very important place among the etiological models of these disorders. Despite the fact that fear conditioning is an adaptative process of great importance for survival, it can turn into clinical relevant when the reactivity to the Conditioned Stimulus (CS) persists in absence of contingency between the CS and the Unconditioned Stimulus (US). By means of classical fear conditioning processes, an anxiety disorder could appear during or after a traumatic event or in a period of significant stress. Nevertheless, not all the persons exposed to this type of events end up developing a disorder. Some studies have demonstrated that patients with anxiety disorders are characterized by a high conditionability and resistance to extinction in anxiety patients compared to healthy controls suggesting that patients are characterized by en enhanced conditioning and that this is one of the reasons for which, in situations of exhibition to aversive incidents, only some individuals go on to develop pathological fears, whereas others show an adaptative response of fear. Many of these studies have use the startle reflex as an index of emotional activation. It consists of a defensive sudden response that many animal species present in presence of an intense and unexpected stimulus. In humans, it can be measured very simply by registering the electromyographic response in the orbicularis oculi muscle. The increase of the startle reflex when an individual is experiencing fear or anxiety is named fear potentiated startle. During the last years, it has been converted into a very useful tool for traslational investigation of anxiety disorders. Up to recent dates, most of the published studies with humans using classical conditioning paradigms have used evolutionarily “unprepared” stimuli to be conditioned, and many have not demonstrated an enhanced conditioning in anxiety patients. This alerts us of the importance to use paradigms that take into account unconditioned stimuli relevant to the disorder object of study. The overall goal of the present dissertation was to investigate fear conditioning processes in social anxiety using the fear potentiated startle in patients with social anxiety compared to patients with panic disorder with agoraphobia and healthy controls. To address this goal, we used a novel paradigm developed by Lissek et al. (2008) in which neutral facial expressions from three female actors served as the CS and were paired with one of three types audiovisual stimuli: insults and critical facial expressions (USneg); comments and neutral facial expressions (USneu); and compliments and positive facial expressions (USpos). Our results did not demonstrate an enhanced conditioning among patients with social anxiety compared to patients with panic disorder with agoraphobia and healthy controls. It is plausible that other associative (e.g. fear extinction) and non-associative processes (e.g cognitive and attentional processes) play a greater role in explaining social anxiety rather than enhanced fear conditioning.

The mesolimbic dopaminergic pathway plays an important role in the genesis of emotional arousal and behavioral activation in response to stimuli that provide a reward. This neural circuitry is also active in the early stages of learning and stabilization of addictive behavior due to substances abuse. Isolated animals have a different sensitivity to natural or artificial reinforcers. Accordingly, experimental evidences suggest that exposure to stress can deeply modify eating behavior. In light of these evidences the aim of this study was to investigate the influence of a chronic stress, like social isolation at weaning, on the sensitivity of mesocorticolimbic dopaminergic neurons to anticipation and consumption of food. Rats have been food restricted using a protocol that consists in training the animals to consume their meal for only two hours for day. Using vertical microdialysis, extracellular concentrations of dopamine in response to anticipation and consumption of food were measured both in the mPFC and the NAC. In PFC of GH rats extracellular DA increased (+180%) 80 minutes before food presentation showing the maximal increase (+350%) during food intake. On the contrary, in the NAc of GH rats no significant changes were observed. In SI animals trained to food restriction the increase in mPFC DA output observed in GH animals was completely blunted, while, in the NAc, 40 min before the presentation of the food, a significant increase in extracellular concentrations of DA was observed. Our results show that exposure to chronic stress modified the response of mesocortico-limbic dopaminergic neurons to an enjoyable stimulus and suggest that these changes might be important to explain the greater sensitivity to abuse that is observed in individuals subjected to stressful stimuli. This underlying alteration in brain function might be a crucial mechanism that predisposes individuals to impulsive behavior and increases the risk of developing addiction.

This thesis investigated with regard to the perception of abstract and social stimuli: (1) What constitutes a visual pattern? (2) Whether people possess a proclivity towards one particular pattern type. (3) When is patterning imposed or detected by the visual system? The abstract stimuli consisted of checkerboard patterns and the social stimuli consisted of faces or social groups. Initially the term "pattern" was defined as an image that contains redundant information. This was illustrated by a bias when defining patterns by members of the public towards images that contain both repeated and reflective symmetry, or a low number of possible variants and therefore reduced information content, i. e. more redundancy. Similarly reflective symmetry was identified as a key property in defining faces. The effect of symmetry type on early visual processing was investigated further in a series of backward masking experiments on both abstract and facial stimuli (Chapters 6& 7). The results of the masking experiments suggest a bias during early visual processing for patterns that contain symmetry (i. e. repetition or reflection), or share common fate compared with randomly generated patterns or distorted faces. A top-hemifield and LVF bias was observed in the early detection of patterns. Patterns that take advantage of these properties such as the eyes within the face were suggested as having a perceptual advantage. Patterning appears to be imposed at all stages of visual processing. At early stages of visual processing, repetition (and in the face the eyes) was observed as having an early perceptual advantage over reflection (and in the face the mouth). However at later stages of processing repetition appeared to be processed serially and no longer had a perceptual advantage over reflection (ISIs >42ms). Reflection was suggested as having a perceptual advantage post V1 (ISIs >96ms). Patterning continues throughout a visual scene from the local level to the global level, as such both the human face and human social groups can be perceived as patterns. This was illustrated by a series of experiments investigating the effect of patterning on the perception of images presented in the periphery of a scene (Chapter 8).

Converging evidence from several different species has led to the proposal that some newborn vertebrates, including humans and domestic chicks, have visual predispositions to attend to the head region of conspecifics (or of animals of other species that share similar characteristics) (Johnson and Horn 1988; Morton and Johnson, 1991; Sugita 2008). More specifically it has been claimed that these newborn preferences are (i) domain-relevant to the extent that other naturally occurring stimuli do not draw attention in the same way, (ii) are not based on rapid early learning, but are present from birth/hatching, and (iii) may be mediated by phylogenetically ancient brain routes common to many vertebrates. One of the most common criticisms of the work supporting domain-relevant face biases in human newborns is that the majority of the studies conducted (with some notable exceptions) regard newborns of more than a few hours old. Thus, it remains possible that very rapid early learning contributes to the specificity of some of the effects observed (Nelson, 2001). This criticisms of the data from human newborns can be addressed by testing newly hatched visually-deprived chicks whose preference for visual stimuli can be assessed prior to any other visual experience with faces, a procedure obviously not viable with human newborns for ethical reasons. The main aim of present study is thus to investigate from a new perspective and employing an animal model (the domestic chick) a long-debated issue: the specificity vs. non-specificity of the perceptual factors involved in face preferences. One central issue in cognitive science is how brain processes knowledge of specific domains, as for example the visual information regarding faces. Some existing evidences seem to indicate that faces are processed by anatomically and/or functionally dedicated domain-specific brain circuits, in humans and possibly also in animals. This idea seems also to be consistent with the striking processing abilities that human beings have demonstrated in face perception. It seems plausible that, because of the relevance of faces for social life, natural selection led to the evolution of innate face-specific devices that are available prior to any postnatal experience. In fact, a number of studies have demonstrated that, even from a few hours or minutes after birth, a schematic pattern representing an upright face elicits greater visual attention in human newborns than do similar stimuli presenting the same internal face-features in scrambled positions or arranged upside-down (see Morton and Johnson, 1991 for a review). According to Morton & Johnson (1991) this evidence would indicate that human newborns respond to the unique structural configuration of the face (i.e. to facedness) due to a face-detecting mechanism (CONSPEC) that contains a configural representation of the structure of the face’s inner features (three darker areas in an upside-down triangular configuration). Similarly, domestic chicks have been shown to posses an unlearned representation for the appearance of a social object. Such a representation would guide the imprinting process ensuring that chicks would imprint on an animate object instead of on an inanimate feature of the environment. In particular, this unlearned representation of the appearance of a social object would include a very broad structural description of the features contained in the head region of a vertebrate creature (e.g. Johnson & Horn, 1988). It has thus been hypothesised that the same mechanism described to explain face preferences in newborn babies (CONSPEC) would underlie also spontaneous preferences of visually naïve chicks (Morton and Johnson, 1991). However, in the human developmental literature it has often been debated whether newborns’ preference for faces would not be simply the secondary effect of some more general and not domain-specific visual preference displayed by newborn vertebrates. This kind of domain-general preference would direct the organism’s attention toward any stimulus presenting a certain physical attribute, regardless of whether this stimulus is a face or a non-face object (Acerra, Burnod and de Schonen, 2002; Kleiner, 1987; Macchi Cassia et al., 2008; Simion et al., 2002; Turati et al., 2002). In my thesis I will thus assess the role of three perceptual properties (that are considered influential in the developmental literature) in determining face preferences in visually naïve domestic chicks. The role of the vertical asymmetry of inner elements Recently, in the developmental literature, it has been argued that newborn infants’ preferences for faces could be a secondary effect determined by non-specific biases due to constraints imposed by the immature visual system of the child. In particular, Turati et al. (2002) provided evidence that the preference for face-like stimuli could be determined by an “up-down bias” (Simion et al., 2002) that directs the babies’ attention toward any configuration presenting more elements in its upper part (a “top-heavy configuration”, as opposed to a “bottom-heavy configuration”, presenting more elements in its lower part). Thus, we decided to investigate whether visually naive domestic chicks spontaneously prefer schematic faces or other top-heavy stimuli and whether such a preference is determined by an up-down bias, as suggested by some literature on newborn babies (Turati et al., 2002). Eggs were incubated and hatched in the darkness and after hatching, for about 24 h, chicks were placed in an uniform white cage whose walls and floor were made of opaque white paper. The only stimulus available to chicks during this rearing period was an artificial orange cardboard imprinting object that presented an identical outline with respect to stimuli that will be employed at test (the outline of a schematic face and neck), but no inner feature. Thus, the imprinting object could not provide chicks with any bias for one of the test stimuli or with any information regarding faces’ inner features. During the second day of life chicks underwent a spontaneous preference test, in which each chick had to choose between one of two stimuli that were simultaneously presented at the two opposite ends of a longitudinal runway. The runway was divided into three virtual sectors. At the beginning of the test each chick was placed in the central sector of the apparatus. In order to approach one of the two stimuli the chick had to leave the central sector of the apparatus and enter one of the two lateral sectors adjacent to the stimuli. Thus, entrance and residence of the chick in one of the side compartments indicated a preference for the adjacent object. The test lasted for 6 minutes. Stimuli employed at test were identical to the imprinting object in size, shape and colour, but presented three inner features (three black squares) that were absent in the imprinting object. The two stimuli in each test-pair differed from one another only in the configuration created by the three black squares (in line with standard stimuli used in the developmental literature). Changing the disposition of the three inner elements it was thus possible to test chicks preferences for face-like vs. non-face like objects controlling also for the role of the up-down bias. Each chick was tested only once and was thus exposed to only one pair of stimuli. With this procedure we demonstrated that chicks prefer to approach a schematic face-like configuration similar to those used in newborn studies with respect to another equally top-heavy, but non-face-like, stimulus (Exp. 1). In line with this result, in a second experiment chicks did not show any evidence of a preference for a top-heavy stimulus over a bottom-heavy stimulus, if none of them represents a face (Exp. 2). Moreover, chicks preferred to stay near a bottom-heavy and face-like stimulus over a top-heavy non-face-like one (Exp. 4). Thus, results obtained in this first cycle of experiments demonstrated that domestic chicks, that are visually naïve with respect to faces’ inner structure, show a spontaneous preference for schematic face-like stimuli that resemble the representation of a face as theorised by Morton and Johnson (1991). Moreover, the vertical asymmetry of inner elements (i.e. the up-down bias, Simion et al., 2002; Turati et al., 2002) does not seem to have a crucial role in the expression of this preference in the animal species that we tested. The role of the spatial frequencies composing stimuli During the past decades another alternative interpretation, based on the so called linear system model (LSM, e.g. Kleiner, 1987), has been proposed to explain face preferences in newborn babies, as opposed to the CONSPEC model proposed by Morton and Johnson (1991). According to this interpretation (confirmed also by the results of a recent neural network model by Acerra, Burnod and de Schonen, 2002) faces would elicit preferential attention in newborn babies simply because they happen to be composed of the range of spatial frequencies more visible to newborns. In previous studies existing in the literature, stimuli were controlled for properties such as vertical symmetry or for the presence of structure (Morton and Johnson, 1991; Farroni et al., 2005; Rosa Salva, Regolin and Vallortigara, 2009). The research conducted in similar studies already generated a good amount of evidence for the role of the above mentioned properties. We thus decided to concentrate our efforts on the role of another potentially relevant perceptual property, namely, spatial frequency composing stimuli. The use of stimuli that exactly match spatial frequencies between face-stimuli and control-stimuli, comparing faces to frequency matched visual noise, is already a common standard in works investigating neural correlates of face perception (Csibra et al., 2004; Blasi et al., 2007). However, to the best of our knowledge, this approach has not yet been systematically applied to the investigation of behavioural preferences in newborn babies and domestic chicks. We thus decided to fill this gap between behavioural and neuroimaging studies. In a recent study (Rosa Salva et al., submitted) we were able to demonstrate that newborn babies show a preference for looking at faces with respect to visual noise stimuli that were matched in terms of their component spatial frequencies. In Expt. 5 of my thesis we thus decided to run a comparative study in order to be able to directly compare data obtained in newborn babies and visually naïve domestic chicks, tested with comparable procedures and identical stimuli. The experimental procedures were the same as those described in the previous session, with the exception that no imprinting stimulus was provided to the chicks. Stimuli consisted in a colour photographic image of a human face and in a frequency matched noise stimulus. Domestic chicks displayed a clear preference for the face-like stimulus. The strength of this preference was comparable to that displayed by newborn human babies. The results of the present research demonstrated that analogue effects can be obtained in both visually deprived domestic chicks and human newborn babies, in that both species show a preference for images of faces. Moreover, such a preference is, in both species, independent from component spatial frequencies. Thus, the present study extends the existing analogy between results obtained in newborn babies and domestic chicks (Johnson and Horn, 1988; Morton and Johnson, 1991; Rosa Salva, Regolin and Vallortigara, 2009), confirming the validity of use of the domestic chick as an animal experimental model to investigate issues connected with the developmental literature. Finally, results obtained showed that the preference for faces observed in domestic chicks is not species-specific (in fact chicks’ preferences could be elicited by a human face). This confirms previous evidence suggesting the presence of a very broad template for the detection of faces in this species (Johnson and Horn, 1988). Effects originated by contrast reversal In recent years it has been demonstrated that contrast reversal eliminates the preference of newborn babies for schematic faces. The normal preference for faces can however be made to remerge by adding a pupil-like dot within the schematic face features (Farroni et al., 2005). These results have been interpreted as due to the fact that the mechanisms underling face preference have been selected to identify faces under natural (top-down) illumination. Such mechanisms are thus sensitive to the light-shadow pattern generated on faces by such conditions (the eye and mouth regions are recessed on a face and therefore appear to be darker than other parts of the face). As a consequence, infants should show no preference for face-like patterns where the elements within the face are lighter than the background, because those elements would indicate protrusions rather than recesses for their visual system (Farroni et al., 2005). We decided to investigate the effect of contrast reversal on the preference for schematic face-like configurations displayed by chicks. The experimental procedure was the same as that described for experiments 1-4. Stimuli employed were obtained from those used in Expt. 1 (where a preference for the face-like stimulus was observed), and consisted in two top-heavy configurations, of which only one represented a face. Stimuli employed in Expt. 6 were identical to those used in Expt. 1, with the relevant exception that they presented a reversed contrast (they were made of lighter inner features on a darker face background). No preference for one of the two stimuli was observed. In Expt. 7, after Farroni et al. (2005), we introduced a pupil-like dot within the lighter inner features of both stimuli. This was done in order to try to restore the initial preference for the face-like stimulus observed in Expt. 1 using stimuli with “normal” contrast polarity. On the contrary, if anything, a preference for the non-face-like stimulus was observed in the present experiment. We interpreted this result as due to the fact that chicks are innately scared of stimuli resembling a pair of eyes. This is especially true for stimuli having a darker pupil within a lighter iris, because such stimuli look predator-like to them (Gagliardi, Gallup and Boren, 1976). Chicks, would thus avoid the face-like stimulus because its two upper features would resemble a pair of predators’ eyes. We tested this hypothesis in Expt. 8, by increasing the pupil-to-iris ratio of our stimuli in order to reach the ratio that is most effective in determining a fear reaction in chicks. With this manipulation results obtained in the previous experiment were confirmed and extended, showing again a preference for the non-face-like stimulus. Moreover, in Expt. 9, we investigated brain lateralization using the same stimuli as in Expt. 8, but testing chicks in monocular vision condition (in chicks this is an effective way for limiting visual processing to the hemisphere contralateral to the eye in use). We hypothesised that the fear reaction elicited by the face-like stimulus should be more pronounced in chicks using their right hemisphere (specialized for fear reactions to the eye-gaze of predators, Rosa Salva, Regolin and Vallortigara, 2007). Some of the results obtained in Expt. 9 were in favour of this hypothesis. As a final control (Expt. 10) we presented chicks with a pair of stimuli that had the normal direction of contrast polarity for a face (i.e. presented darker inner features on a lighter background), but had also an eye-like appearance of their inner features. No preference whatsoever was observed, this was possibly interpreted as a consequence of the simultaneous presence of two opposite tendencies: a social preference for the face-like configuration, now emerged again thanks to the normal direction of contrast polarity, and a fear reaction elicited by its eye-like features. Finally, in Expt. 11 we tested monocular chicks using identical stimuli to those of Expt. 10, in order to investigate brain lateralization. In this final experiment, an opposite tendency was observed for chicks using their right hemisphere with respect to what observed in Expt. 9. In fact, chicks using their right hemisphere tended to prefer again the face-like configuration. This is not completely unexpected if two things are taken in consideration. First of all, the right hemisphere is not only dominant for fear reactions to eye gaze, but also for recognition of social partners (e.g. Daisley et al., 2009, for a review). Moreover, the face stimulus used in the present experiment was conspicuously “more social” than that used in Expt. 9, because it presented the normal direction of contrast polarity for a face. This probably caused the right hemisphere to be driven by the social nature of the stimulus rather than by its aversive predator-eye-like inner features. Results of this last cycle of experiments show that, in line with the evidence available in developmental literature, contrast reversal is effective in suppressing chicks’ preferences for schematic faces. However, adding a pupil-like eye dot on inner face features had an opposite effect in chicks with respect to newborn babies. In fact, in chicks this manipulation elicited a preference for the non-face-like stimulus, possibly due to an anti-predator fear reaction. Overall, my results are consistent with the presence in chicks of an unlearned mechanism for the detection of faces based on a very broad template representing the structure of a face (i.e. CONSPEC, Morton and Johnson, 1991). Moreover, contrary to evidence obtained in newborn babies (Turati et al., 2002), it seems that chicks’ preferences for faces are not influenced by the vertical asymmetry of inner elements. On the other hand, both chicks and human babies (Rosa Salva et al., submitted) seem to prefer faces regardless of their component spatial frequencies. Similarly, contrast reversal effectively abolishes the preference for faces in both human newborns (Farroni et al., 2005) and domestic chicks.
Sulla base di evidenze sperimentali ottenute in diverse specie animali è stato teorizzato che i piccoli di alcuni vertebrati possano avere predisposizioni precoci o innate per prestare attenzione alla regione della testa e del volto dei conspecifici (o di altri animali che ne condividano la struttura generale) (Johnson e Horn 1988; Morton e Johnson, 1991; Sugita 2008). In particolare è stato teorizzato che tali predisposizioni siano (i) di natura dominio-specifica in quanto altri stimoli presenti in ambiente naturale non attraggono l’attenzione con la stessa efficacia dei volti, (ii) non siano basate su fenomeni di apprendimento precoce, ma piuttosto siano presenti sin dal momento della nascita/schiusa, e (iii) siano mediate da sistemi neurali filogeneticamente antichi comuni a diverse specie di vertebrati. Una delle principali critiche ai lavori che hanno dimostrato la presenza di preferenze dominio-specifiche per i volti nei neonati della specie umana è legata al fatto che, per lo più, tali lavori abbiano testato neonati di alcune ore di vita. Per tale ragione non è mai stato possibile escludere il fatto che le preferenze per i volti riscontrate nei neonati fossero dovute in realtà ad effetti di apprendimento legati all’esperienza avuta dai neonati stessi con i volti (Nelson, 2001). Tale critica può essere tuttavia aggirata da studi che impieghino pulcini di pollo domestico, deprivati di esperienza visiva riguardo ai volti, come modello animale per investigare la presenza di preferenze spontanee per i volti. Lo scopo del mio lavoro di tesi è perciò quello di investigare da una nuova prospettiva ed usando un modello animale (il pulcino domestico) un problema a lungo dibattuto in letteratura: ovvero la specificità o non specificità dei fattori percettivi coinvolti nelle preferenze per i volti. Un tema centrale nelle scienze cognitive è rappresentato dalle modalità con le quali il cervello elabora la conoscenza relativa a degli specifici domini, come ad esempio l’informazione visiva riguardante i volti. Alcune evidenze presenti in letteratura sembrano indicare che i volti siano processati da circuiti cerebrali specificamente dedicati sia nell’uomo, che probabilmente negli animali. Questa idea è anche coerente con le incredibili capacità di elaborazione che la nostra specie dimostra per le informazioni relative ai volti. Sembra perciò plausibile che, a casa della rilevanza dei volti per la vita sociale, la selezione naturale abbia portato all’evoluzione di meccanismi specifici deputati all’elaborazione dei volti e disponibili in modo non appreso. Infatti, numerosi studi hanno dimostrato che neonati umani di poche ore o minuti di vita preferiscono guardare uno stimolo schematico rappresentante un volto rispetto ad uno stimolo simile in cui i medesimi elementi interni componenti il volto sono presentati in posizioni scrambled o capovolte (Morton e Johnson, 1991). Secondo il modello proposto da Morton e Johnson (1991), questi risultati indicherebbero che i neonati umani preferiscono osservare qualsiasi stimolo che presenti la peculiare struttura di un volto, grazie ad un meccanismo innato per la detezione dei volti (CONSPEC), il quale conterrebbe una rappresentazione della struttura di un volto e della disposizione spaziale delle sue componenti interne. Tale rappresentazione potrebbe semplicemente comprendere la presenza di tre aree più scure su fondo chiaro poste in corrispondenza dei vertici di un invisibile triangolo rovesciato, ovvero in posizioni corrispondenti ad occhi e bocca di un volto. In linea con il modello proposto da Morton e Johnson (1991) anche i pulcini di pollo domestico sembrano possedere una rappresentazione innata dell’aspetto di un con specifico o di un oggetto sociale in generale. Tale rappresentazione guiderebbe il processo di apprendimento noto come imprinting, assicurando che l’animale sviluppi attaccamento per un appropriato compagno sociale e non per un qualsiasi oggetto inanimato presente nell’ambiente. In particolare la rappresentazione di oggetto sociale in possesso dei pulcini includerebbe una generica e schematica descrizione strutturale relativa alla configurazione formata dagli elementi presenti nella regione della testa e del collo di un vertebrato (Johnson e Horn, 1988). E’ stato perciò teorizzato che lo stesso meccanismo descritto per spiegare le preferenze per i volti nei neonati umani (CONSPEC) stia alla base delle preferenze dimostrate dai pulcini privi di esperienza visiva (Morton e Johnson, 1991). Tuttavia, nella letteratura relativa alla psicologia dello sviluppo è stato spesso dibattuto se le preferenze per i volti riscontrate nei neonati della specie umana non siano semplicemente un effetto secondario di un qualche generico bias aspecifico, invece che essere determinate da una preferenza di tipo dominio-specifico per i volti. Questo tipo di preferenza dominio generale dirigerebbe l’attenzione del bambino verso qualsiasi stimolo che presenti un certo attributo fisico, a prescindere dal fatto che tale stimolo sia un volto oppure no (Acerra, Burnod e de Schonen, 2002; Kleiner, 1987; Macchi Cassia et al., 2008; Simion et al., 2002; Turati et al., 2002). Nel mio lavoro di tesi ho perciò deciso di investigare il ruolo di tre proprietà percettive (considerate influenti nella letteratura sulle preferenze per i volti nel neonati umano) nel determinare le preferenze espresse da pulcini di pollo domestico privi di esperienza visiva relativamente a dei volti. Ruolo dell’asimmetria verticale nella distribuzione degli elementi interni Recentemente, in psicologia dello sviluppo, è stato teorizzato che le preferenze dimostrate dai neonati umani per i volti potrebbero essere un effetto secondario determinato da dei bias attentivi di tipo non specifico, dovuti alle limitate capacità del sistema visivo immaturo. In particolare, Turati ed altri (2002) hanno prodotto dati a favore della teoria secondo la quale le preferenze per i volti sarebbero determinate dal cosiddetto “bias up-down” (Simion et al., 2002). Tale bias dirige l’attenzione del neonato verso qualsiasi configurazione che presenti più elementi nella metà superiore dello stimolo (ovvero verso qualsiasi configurazione di tipo “top-heavy”, in opposizione alle configurazioni “bottom-heavy” che presentano più elementi nella parte inferiore). Abbiamo perciò deciso di verificare se pulcini di pollo domestico privi di esperienza visiva relativa ai volti avessero una preferenza spontanea per stimoli rappresentanti volti schematici o per configurazioni di tipo “top-heavy” e se una eventuale preferenza per i volti fosse determinata dal “bias up-down”, come suggerito dalle evidenze relative al neonato umano (Turati et al., 2002). Sono stati testati pulcini nati all’interno del laboratorio da uova incubate e schiuse al buio. Durante le 24 ore successive alle schiusa i pulcini erano allevati in delle gabbie foderate di carta bianca opaca. L’unico stimolo fornito ai pulcini durante tale periodo di allevamento era un oggetto di imprinting artificiale, una sagoma di cartoncino arancione che aveva la stessa forma generale degli stimoli sperimentali poi usati in fase di test (la sagoma schematica di una testa su di un collo, creata da una forma ovoidale posta in cima ad una rettangolare), ma era privo di caratteristiche interne. L’oggetto di imprinting non poteva perciò fornire ai pulcini alcuna fonte di informazione relativa alla struttura interna di un volto. Al secondo giorno di vita i pulcini venivano testati tramite un compito di scelta spontanea nel quale ciascun pulcino doveva scegliere tra una di due configurazioni (stimoli di test) simultaneamente presenti alle due estremità di un apparato longitudinale. L’apparato di scelta era virtualmente diviso in tre settori, e all’inizio del test il pulcino veniva posto in quello centrale. Per avvicinare uno dei due stimoli sperimentali l’animale doveva lasciare il settore centrale dell’apparato ed entrare in uno dei due settori laterali, adiacenti agli stimoli. Per questa ragione l’ingresso e la permanenza del pulcino in uno dei due settori laterali era considerato un indice di preferenza per lo stimolo adiacente. Il test aveva una durata di 6 minuti. Gli stimoli impiegati erano identici all’oggetto di imprinting per forma, colore e dimensioni e differivano da esso per la presenza di tre blob neri che rappresentavano le caratteristiche interne di ciascuno stimolo. I due stimoli in ogni coppia oggetto del test differivano tra loro solo nella disposizione di tali elementi interni (in accordo con gli standard relativi agli stimoli usati in psicologia dello sviluppo per testare le preferenze per i volti). Cambiando la disposizione degli elementi interni era perciò possibile testare le preferenze dei pulcini per stimoli rappresentanti dei volti schematici rispetto a stimoli che non avevano la struttura di un volto, controllando al contempo il ruolo del “bias up-down”. Ciascun pulcino era testato soltanto una volta (partecipava perciò soltanto ad un esperimento ed era esposto solo ad una coppia di stimoli). Tramite questa procedura è stato possibile dimostrare che i pulcini preferiscono approcciare uno stimolo schematico rappresentante un volto (simile a quelli impiegati negli studi sui neonati della specie umana) rispetto ad un altro stimolo egualmente “top-heavy” ma non rappresentante un volto (Exp 1). Coerentemente con questo risultato, in un secondo esperimento i pulcini non hanno dimostrato alcun segno di preferenza per uno stimolo “top-heavy” rispetto ad uno “bottom-heavy”, quando nessuno dei due rappresentava un volto (Exp 2). Inoltre, in un ulteriore esperimento i pulcini hanno preferito stare vicino ad uno stimolo“bottom-heavy” rapprsentante un volto rispetto ad uno “top-heavy”, ma non avente la struttura di un volto (Exp 4). I risultati ottenuti in questo primo ciclo di esperimenti hanno perciò permesso di dimostrare che pulcini domestici privi di esperienza visiva al riguardo hanno una preferenza spontanea per stimoli schematici che ricordano la rappresentazione di volto teorizzata da Morton e Johnson (1991). Inoltre, la asimmetria verticale nella disposizione degli elementi interni (cioè il “bias up-down”, Simion et al., 2002; Turati et al., 2002) non sembra avere un ruolo cruciale nell’espressione di tale preferenza, almeno nella specie da noi testata. Ruolo delle frequenze spaziali componenti gli stimoli Negli ultimi decenni è stata tuttavia proposta anche un’altra interpretazione alternativa per spiegare le preferenze per i volti in opposizione al modello proposto da Morton e Johnson (1991). Tale interpretazione è basata sul cosiddetto linear system model (LSM, Kleiner, 1987). Secondo questa teoria (recentemente avvalorata dai risultati ottenuti tramite un modello neurale da Acerra, Burnod e de Schonen, 2002), i volti sarebbero osservati preferenzialmente dai neonati umani semplicemente perché composti dal range di frequenze spaziali più visibili per i neonati. In precedenti lavori esistenti in letteratura, sono stati impiegati stimoli controllati per proprietà quali la simmetria verticale o la presenza di struttura (Morton e Johnson, 1991; Farroni et al., 2005; Rosa Salva, Regolin e Vallortigara, 2009). Tali studi hanno generato sufficienti evidenze a proposito del ruolo di tali proprietà. Nella presente ricerca abbiamo perciò deciso di investigare il ruolo di un’altra proprietà potenzialmente rilevante, quale le frequenze spaziali componenti gli stimoli. L’uso di stimoli che equiparino le frequenze spaziali tra volti e stimoli di controllo è già uno standard accettato in lavori di neuroimmagine (Csibra et al., 2004; Blasi et al., 2007). Tuttavia, questo approccio non è stato ancora sistematicamente impiegato per l’investigazione di preferenze comportamentali in neonati umani e pulcini domestici. Abbiamo perciò deciso di colmare questo divario presente tra studi comportamentali e di neuroimmagine. In uno studio recente (Rosa Salva et al., sottomesso) siamo stati infatti in grado di dimostrare che neonati umani preferiscono guardare immagini di volti rispetto a stimoli che abbiano il medesimo contenuto in termini di frequenze spaziali. Nel Exp. 5 della mia tesi abbiamo perciò deciso di svolgere uno studio comparativo al fine di paragonare direttamente dati ottenuti in neonati umani e in pulcini privi di esperienza visiva, testati con procedure analoghe e stimoli identici. La procedura sperimentale era la medesima descritta nel paragrafo precedente, con l’eccezione che non veniva fornito alcun oggetto di imprinting ai pulcini. Gli stimoli consistevano in una fotografia a colori di un volto umano ed uno stimolo noise composto dalle medesime frequenze spaziali dello stimolo rappresentante un volto. In tale esperimento pulcini hanno dimostrato una chiara preferenza per lo stimolo rappresentante un volto. L’entità di tale preferenza era inoltre comparabile a quella precedentemente riscontrata nei neonati umani. Il risultato della presente ricerca dimostra che effetti analoghi possono essere ottenuti in pulcini domestici privi di esperienza relativa a dei volti, e neonati umani di pochi giorni di vita, poiché entrambe le specie hanno una preferenza per immagini rappresentanti dei volti. Inoltre, tale preferenza è in entrambe le specie indipendente dalle frequenze spaziali componenti gli stimoli. Perciò, questo studio estende ulteriormente le analogie esistenti tra risultati ottenuti nel neonato umano e nel pulcino domestico (Johnson e Horn, 1988; Morton e Johnson, 1991; Rosa Salva, Regolin e Vallortigara, 2009), confermando inoltre la validità del pulcino come modello animale per lo studio di problematiche originate nell’ambito della psicologia dello sviluppo. Infine, i risultati ottenuti mostrano che la preferenza per i volti osservata nei pulcini di pollo domestico è di tipo non specie specifico (infatti le preferenze dei pulcini potevano essere elicitate anche da un volto umano). Ciò conferma le evidenze precedenti che avevano suggerito la presenza di un template estremamente generico per la detezione dei volti in questa specie (Johnson e Horn, 1988). Effetti dell’inversione della polarità di contrasto Recentemente, è stato dimostrato che invertire la polarità di contrasto elimina le preferenze dei neonati umani per i volti schematici. La normale preferenza per i volti riemerge tuttavia aggiungendo un pupil-like-dot entro gli elementi schematici interni al volto (Farroni et al., 2005). Questi risultati sono stati interpretati come dovuti al fatto che il meccanismo responsabile delle preferenze per i volti è stato selezionato durante l’evoluzione al fine di identificare i volti come essi appaiono in condizioni di illuminazione naturale (ovvero dall’alto). Un simile meccanismo dovrebbe perciò essere sensibile al pattern di luci ed ombre che viene creato sui volti da tale tipo di illuminazione. In particolare, le aree degli occhi e della bocca sono rientranze ed appaiono perciò più scure delle aree circostanti. Per tale ragione i neonati non dovrebbero preferire stimoli rappresentanti dei volti ma aventi polarità di contrasto invertita, perché gli elementi interni del volto sarebbero in tale caso più chiari e non più scuri dello sfondo del volto stesso (Farroni et al., 2005). Abbiamo perciò deciso di studiare l’effetto dell’inversione della polarità di contrasto sulle preferenze per volti schematici che avevamo precedentemente dimostrato in pulcini di pollo domestico (Exp. 1). La procedura sperimentale era la stessa descritta per gli Exp. 1-4. Gli stimoli impiegati erano stati ottenuti manipolando quelli usati nell’Exp. 1 (nel quale era stata dimostrata una preferenza per lo stimolo rappresentante un volto) e consistevano in due configurazioni “top-heavy”, delle quali solo una rappresentante un volto. Nell’Exp. 6 sono state impiegate configurazioni identiche a quelle usate nel’Exp. 1, ma aventi opposta polarità di contrasto (tali configurazioni presentavano infatti tre blob più chiari, le caratteristiche interne del volto, disposti su di uno sfondo più scuro). In questo caso non veniva osservata alcuna preferenza. Nell’Exp. 7, seguendo la procedura di Farroni ed altri (2005), abbiamo introdotto un pupil-like-dot più scuro all’interno dei blob più chiari rappresentanti le caratteristiche interne dei due stimolo. Tale manipolazione era volta a far riemergere l’originaria preferenza per lo stimolo rappresentante il volto (che era stata osservata nell’Exp. 1 usando stimoli aventi “normale” polarità di contrasto). Al contrario, una preferenza per lo stimolo non rappresentante un volto sembrava essere presente nell’Exp. 7. Abbiamo interpretato tale risultato come dovuto al fatto che i pulcini sono spaventati in modo innato da stimoli che rassomiglino ad un paio di occhi di un potenziale predatore. Ciò è particolarmente vero per occhi aventi una pupilla scura su di un iride più chiaro, perché tali stimoli rassomigliano in modo particolare agli occhi di alcuni predatori (Gagliardi, Gallus e Boren, 1976). I pulcini da noi testati nell’Exp. 7 tenderebbero perciò ad evitare lo stimolo volto perché i suoi due elementi interni superiori rassomiglierebbero ad un paio di occhi di predatore. Tale ipotesi è stata testata nell’Exp. 8 accrescendo il rapporto tra le dimensioni di “iride” e “pupilla” fino a raggiungere il rapporto che risulta essere il più efficace nell’elicitare una risposta di paura nei pulcini (Gagliardi, Gallus e Boren, 1976). Tramite tale manipolazione sono stati ottenuti risultati che hanno confermato ed esteso quelli dell’esperimento precedente, dimostrando nuovamente una preferenza per lo stimolo non rappresentante un volto. Inoltre, nell’Exp. 9, è stata indagata la lateralizzazione cerebrale associata a tali effetti. A tal fine sono stati impiegati stimoli identici all’esperimento precedente, ma i pulcini sono stati testati in condizioni di visione monoculare (tale procedura è nella specie da noi impiegata efficace nel limitare l’elaborazione delle informazioni all’emisfero contralaterale all’occhio in uso). La nostra ipotesi era che la reazione di paura indotta dallo stimolo rappresentante un volto avrebbe dovuto essere più pronunciata nei pulcini aventi in uso l’emisfero destro (dominate nelle risposte di paura elicitate dallo sguardo di un potenziale predatore, Rosa Salva, Regolin e Vallortigara, 2007). Alcuni dei risultati ottenuti nell’Exp. 9 hanno supportato tale ipotesi. Come ulteriore controllo (Exp. 10) abbiamo inoltre presentato ai pulcini una coppia di stimoli aventi la normale polarità di contrasto attesa per un volto (cioè aventi elementi interni più scuri rispetto allo sfondo del volto), ma i cui elementi interni presentavano comunque una rassomiglianza con gli occhi di un potenziale predatore. Non è stata in questo caso osservata alcuna preferenza per uno dei due stimoli. Probabilmente ciò è stato dovuto alla compresenza simultanea di due tendenze opposte: la preferenza sociale per la configurazione rappresentante un volto (ora riemersa grazie alla normale polarità di contrasto) e la reazione di paura dovuta all’aspetto simile ad occhi degli elementi interni del volto. Infine, nell’Exp. 11, abbiamo testato pulcini monoculari usando stimoli identici a quelli impiegati nell’Exp. 10, al fine di studiare eventuali effetti di lateralizzazione cerebrale. In questo ultimo esperimento è emersa una tendenza opposta a quella osservata nell’Exp. 9. Infatti, i pulcini aventi in uso l’emisfero destro sembravano avere una preferenza per lo stimolo rappresentante un volto. Questo risultato non è così inaspettato come potrebbe sembrare, se si prendono in considerazione alcuni elementi. Per prima cosa, l’emisfero destro del pulcino non è solo dominante per le risposte di paura eleicitate dallo sguardo di un potenziale predatore, ma anche dominante per il riconoscimento dei partner sociali (review in Daisley et al., 2009). Inoltre, lo stimolo volto usato nell’Exp.11 risulta decisamente più efficace come stimolo sociale di quello usato nell’Exp. 9, poiché presenta la normale polarità di contrasto attesa per un volto. Ciò probabilmente ha fatto si che l’emisfero destro rilevasse la natura sociale di tale stimolo, piuttosto che la natura predatoria data dall’aspetto dei suoi elementi interni simili ad occhi. I risultati di tale ultimo ciclo di esperimenti mostrano come, in linea con le evidenze ottenute nel neonato della specie umana, l’inversione della polarità di contrasto sia efficace nel sopprimere le preferenze per i volti schematici nel pulcino domestico. Tuttavia, l’aggiunta di un pupil-like-dot più scuro entro gli elementi interni del volto ha effetto opposto nel pulcino rispetto alla specie umana. Infatti, nei pulcini tale manipolazione suscita una preferenza per lo stimolo non rappresentante un volto, probabilmente a causa di una reazione di tipo antipredatorio. Nel complesso i risultati da me ottenuti sono coerenti con la presenza nel pulcino di pollo domestico di un meccanismo innato per la detezione dei volti, basato su di una rappresentazione estremamente generica e schematica della struttura di un volto (come quella ipotizzata per CONSPEC, Morton e Johnson, 1991). Inoltre, contrariamente alle evidenze ottenute nel neonato umano (Turati et al., 2002), sembra che le preferenze espresse dai pulcini per i volti non siano influenzate dall’asimmetria nella disposizione degli elementi interni. D’altro canto, sembra che le preferenze per i volti, riscontrate sia nei pulcini che nei neonati umani (Rosa Salva et al., sottomesso), siano indipendenti dalle frequenze spaziali componenti gli stimoli. Similmente, in entrambe le specie l’inversione della polarità di contrasto elimina tali preferenze.

Adolescent shoplifting has provoked limited and somewhat controversial perspectives within the sociological and psychological literature. These controversies center around the empirical variables used for analysis. A companion argument focuses on the subjective and objective measurement of these variables. This research explicated variables from the sociological literature to test their relationship, using multiple linear regression, to adolescent shoplifting behavior. These variables and situational stimuli were operationalized in a simultaneous model to demonstrate a proximate occurrence of the attitude-situation-behavior reciprocal. This reciprocal is a learning theory which suggests that direct and vicarious experiences accompanied by rewards and punishment, in one's environment, lead to the acquisition of specific beliefs, attitudes and behavior toward a situation. This research contends that beliefs and attitudes toward the situation, rather than the bonding, peer association and other factors, shape adolescent shoplifting behavior. The situational stimuli variables were perceived empirically as being the major reciprocal element that maximized and/or minimized the adolescent's attitude toward shoplifting. The reciprocals are expressed as: SF = f(B, PA, PA, PR, N, N, ATT, S, Age, Race). An anonymous self-report questionnaire was administered to N = 312 Portland adolescents ranging in ages between 13 and 17. These youths were sampled at various neighborhood youths service centers, mall stores and Fred Meyer. The S-R elicited the youths' perceptions and attitudes to the explicated dimensions of the variables. The research results confirmed the situational stimuli correlate for adolescent 'snitch' shoplifting. Statistical results validate the progressive involvement and drift propositions

Perceptual load theory, together with the surround-suppression model suggest that stimulus surrounding attended stimuli is suppressed, especially if perceptual load is high. This study attempts to map surround-suppression using electroencephalography to measure neural activity related to suppression at four surrounding locations (2°, 3°, 4° and 6° from fixation). Color and orientation was used to manipulate load, and the effect of load was controlled through behavioral and neural measures using event related potentials. Our results demonstrate no statistically supported effect of load in behavioral data or SSVEP data, but unexplained increased neural amplitude of an early visual component (i.e. N1) in the (hypothesized) low load condition.

According to the DSM-IV- TR (American Psychiatric Association, 2000), one of the core deficits in autism is in the impairment of social interaction. Some have suggested that underlying these deficits is the reality that individuals with autism do not find social stimuli to be as reinforcing as other types of stimuli (Dawson, 2008). An interesting and growing body of literature supports the notion that symptoms in autism may be caused by a general reduction in social motivation (Chevallier et al., 2012). A review of the literature suggests that social orienting and social motivation are low in individuals with autism, and including social motivation as a target for therapeutic intervention should be pursued (Helt et al., 2008). Through our understanding of learning processes, researchers in behavior analysis and related fields have been able to use conditioning procedures to change the function of neutral or ineffective stimuli, including tokens (Ayllon & Azrin, 1968), facial expressions (Gewirtz & Pelaez-Nogueras, 1992) and praise (Dozier et al., 2012). The current study aimed to use operant and respondent procedures to condition social stimuli that were empirically shown to not be reinforcing prior to conditioning. Further, this study aimed to compare the two procedures in their effectiveness to condition social stimuli to function as reinforcers, and in their maintenance of effects over time. Using a multiple-baseline, multi-element design, one social stimulus was conditioned under each procedure to compare the different response rates following conditioning. Finally, the study sought to determine if conditioning social stimuli to function as reinforcers had any effect on the social functioning of young children with autism. Six children diagnosed with autism between the ages of 18 months and 3 years participated. Results show that the respondent procedure (pairing) resulted in more robust and enduring effects than the operant procedure (Sd procedure). Results of a social communication assessment (ESCS, Mundy et al., 2003) before and after conditioning demonstrate gains in all areas of social communication, particularly in the areas of initiating and responding to joint attention.

Numerous studies have linked dispositional mindfulness to enhanced emotion regulation. The present research examined dispositional mindfulness as a predictor of emotion regulation in social affective contexts. Participants completed passive viewing and Emotional Go/No-Go tasks involving social affective stimuli (happy, neutral, and fearful facial expressions). Event-related potentials (ERPs) and behavioral responses were examined to discern whether dispositional mindfulness predicted differential neural and behavioral responses indexing attention to, awareness of, and inhibitory control over automatic responses to affective social stimuli. Dispositional mindfulness predicted larger (more negative) N100, N200 and No-Go N200 amplitudes during the Emotional Go/No-Go task, but was not associated with amplitude of the Late Positive Potential during the passive viewing task. Dispositional mindfulness also predicted faster response times (RT) to target stimuli that were not attributable to a speed-accuracy tradeoff. No relations were found between mindfulness and RT variability nor accuracy. Implications for understanding mindfulness and early processes of social emotion regulation are discussed.

La guerra è evento, tema, topos che più di ogni altro induce la fiction – stimolando, si direbbe, istanze superegoiche di fedeltà storica – a premere sui propri confini, inibire lo spazio dell’invenzione e confondersi con forme di scrittura non finzionali (memorialistica, diario, reportage…). Ma in che modo e in che misura la sua rappresentazione letteraria (e teatrale, cinematografica, a fumetti…) è mutata – in quanto a tono e strategie, a grado di deformazione del reale noto e condiviso – nello spazio di un secolo che ha visto trasformate anche le strategie belliche, la copertura mediatica e di conseguenza l’immaginario collettivo legato ai conflitti? Il volume pensato e curato da Nicola Turi, mentre approfondisce in relazione al tema singoli percorsi d’autore noti e meno noti, italiani e non (da Leopardi a Zanzotto, da Gadda a Calvino, da Salsa a Dessí, da Luzi e Fenoglio fino a Leavitt, Eisner e Celestini), stimola ed elabora una riflessione profonda sullo smarrimento e la naturale attrazione del gesto artistico (di volta in volta all’insegna dell’ironia feroce, della disperata incredulità, dell’elegiaca testimonianza) per il male, il dolore, il marziale stravolgimento del contesto umano, sociale e politico.

Dopamine and social cooperation describes how, in humans, dopamine-innervated brain areas or cell body regions are activated during cooperative social interactions, suggesting that social stimuli may be primary incentive stimuli. Lactating female rats lever press for access to their pups, nucleus accumbens dopamine is released during maternal behavior, and accumbens dopamine lesions decrease maternal behavior, implicating incentive learning in maternal care. Adult male Syrian hamsters learn a preference for a place associated with a female scent that increases nucleus accumbens dopamine and a dopamine receptor antagonist blocks the learning implicating dopamine in incentive learning in sexually mature males. In songbirds, striatal dopamine release is associated with directed song used to attract a mate; dopamine may influence the incentive value of the mate. Dopamine is linked to social behavior in reptiles, amphibians, fish, and insects. Dopamine-mediated incentive learning may contribute to the organization of socially cooperative behavior in many species.

AbstractIn this chapter we explore how collaborative meanings can be made as teachers and young children (six-year-olds) engage together in reading wordless picturebooks. The activity of talking about these visual texts was a central part of the DIALLS project as children joined together not only to make meaning from them, but also use them as stimuli for deeper philosophical thinking about themes around living together and social responsibility. The discussions gave children the opportunity to engage in ‘genuine dialogue’ (Buber in Between man and man, trans. R.G. Smith. Routledge, London, 1947), as they co-constructed meaning from the narratives and as they then related the themes within them to their own lives, values and identities.

AbstractChildren with autism spectrum disorder (ASD) face the challenge of social interaction and communication, leading to them often requiring significant support from others in their daily lives. This includes challenges like basic communication to convey their emotions to comprehension in early education. To aid with their early development, we propose Furekit, a wearable toolkit that encourages physical interaction via audio and tactile stimuli. Furekit can be attached to various parts of the body, can be operated wirelessly, and is equipped with both a speaker and a vibrotactile actuator. The audio and tactile stimuli are triggered when touched via a conductive pad on the surface, aiming to aid these children’s learning and social experience. From our conducted workshop with children with ASD, we found that Furekit was well-received and was able to encourage their spontaneous physical movement. In the workshop, Furekit shows its potential as an educational and communication tool for children with ASD.

Socially Assistive Robots (SARs) are a class of robots that are at an intersection between the class of assistive robots and that of interactive social robots. Besides providing some kind of assistance, SARs can provide user stimuli through interaction with the robot. SARs have been explored to assist in different healthcare therapies. This work is based on an open-source SAR called EVA. We have extended EVA’s capabilities for multimodal interaction and integration with light sensory effects. This paper presents our current research and future steps to use EVA for healthcare therapies.

A key predictor of an autism spectrum disorder (ASD) diagnosis is attenuated attention to social stimuli.1 Thus far, the reasons underlying this abnormality are unknown: some have hypothesized reduced social motivation2 while others have suggested aberrant oculomotor function in affected individuals.3