Michael Ewbank

Background: Autism Spectrum Conditions (ASC) are associated with a range of perceptual atypicalities, including abnormalities in gaze processing. Pellicano and Burr (Trends Cogn Sci 16(10):504-10, 2012) have argued that these atypicalities might be explained within a Bayesian framework, in which perception represents the combination of sensory information with prior knowledge. They propose that the Bayesian priors of individuals with ASC might be attenuated, such that their perception is less reliant on prior knowledge than neurotypical individuals. An important tenet of Bayesian decision theory is that increased uncertainty about incoming sensory information will lead to a greater influence of the prior on perception. Consistent with this, Mareschal et al. (Curr Biol 23(8):717-21, 2013) showed that when noise is added to the eyes of a face (increasing uncertainty about gaze direction), gaze is more likely to be perceived as direct. Methods: We adopted the same paradigm as Mareschal et al. to determine whether the influence of a prior on gaze perception is reduced in neurotypical participants with high numbers of autistic traits (experiment 1) and in individuals with a clinical diagnosis of ASC (experiment 2). Participants were presented with synthetic faces and asked to make a judgement about the relative gaze directions of the faces. Uncertainty about gaze direction was manipulated by adding noise to the eyes of a face. Results: Consistent with previous work, in both experiment 1 and experiment 2, participants showed a bias towards perceiving gaze as direct under conditions of uncertainty. However, there was no evidence that the magnitude of this bias was reduced either in the ASC group or in neurotypical controls with a high number of autistic traits.

Repeated viewing of a stimulus causes a change in perceptual sensitivity, known as a visual aftereffect. Similarly, in neuroimaging, repetitions of the same stimulus result in a reduction in the neural response, known as repetition suppression (RS). Previous research shows that aftereffects for faces are reduced in both children with autism and in first-degree relatives. With functional magnetic resonance imaging, we found that the magnitude of RS to faces in neurotypical participants was negatively correlated with individual differences in autistic traits. We replicated this finding in a second experiment, while additional experiments showed that autistic traits also negatively predicted RS to images of scenes and simple geometric shapes. These findings suggest that a core aspect of neural function-the brain's response to repetition-is modulated by autistic traits.

Autism spectrum conditions (ASC) are associated with a number of atypicalities in face processing, including difficulties in face memory. However, the neural mechanisms underlying this difficulty are unclear. In neurotypical individuals, repeated presentation of the same face is associated with a reduction in activity, known as repetition suppression (RS), in the fusiform face area (FFA). However, to date, no studies have investigated RS to faces in individuals with ASC, or the relationship between RS and face memory. Here, we measured RS to faces and geometric shapes in individuals with a clinical diagnosis of an ASC and in age and IQ matched controls. Relative to controls, the ASC group showed reduced RS to faces in bilateral FFA and reduced performance on a standardized test of face memory. By contrast, RS to shapes in object-selective regions and object memory did not differ between groups. Individual variation in face-memory performance was positively correlated with RS in regions of left parietal and prefrontal cortex. These findings suggest difficulties in face memory in ASC may be a consequence of differences in the way faces are stored and/or maintained across a network of regions involved in both visual perception and short-term/working memory.

Background: Autism Spectrum Conditions (ASC) are associated with a range of perceptual atypicalities, including abnormalities in gaze processing. Pellicano and Burr (Trends Cogn Sci 16(10):504-10, 2012) have argued that these atypicalities might be explained within a Bayesian framework, in which perception represents the combination of sensory information with prior knowledge. They propose that the Bayesian priors of individuals with ASC might be attenuated, such that their perception is less reliant on prior knowledge than neurotypical individuals. An important tenet of Bayesian decision theory is that increased uncertainty about incoming sensory information will lead to a greater influence of the prior on perception. Consistent with this, Mareschal et al. (Curr Biol 23(8):717-21, 2013) showed that when noise is added to the eyes of a face (increasing uncertainty about gaze direction), gaze is more likely to be perceived as direct. Methods: We adopted the same paradigm as Mareschal et al. to determine whether the influence of a prior on gaze perception is reduced in neurotypical participants with high numbers of autistic traits (experiment 1) and in individuals with a clinical diagnosis of ASC (experiment 2). Participants were presented with synthetic faces and asked to make a judgement about the relative gaze directions of the faces. Uncertainty about gaze direction was manipulated by adding noise to the eyes of a face. Results: Consistent with previous work, in both experiment 1 and experiment 2, participants showed a bias towards perceiving gaze as direct under conditions of uncertainty. However, there was no evidence that the magnitude of this bias was reduced either in the ASC group or in neurotypical controls with a high number of autistic traits.

Abstract. People sometimes appear to represent graphical information by analogy to space. In this paper we consider the extent to which the tendency to represent information by analogy to space calls on spatial resources. We also examine whether people who represent ...

Autism Spectrum Conditions (ASC) are characterized by a range of perceptual atypicalities, including abnormalities in gaze processing. Pellicano and Burr (2012) recently proposed that perceptual atypicalities might be a consequence of attenuated priors in ASC (i.e. reduced influence of prior knowledge on the perception of sensory information). Evidence from neurotypical populations indicates that under conditions of uncertainty (created by adding noise to the eyes of face stimuli), gaze is more likely to be perceived as direct (Mareschal et al., 2013), suggesting that humans have a prior expectation that other people's gaze is directed toward them. Here we adopted the same paradigm to address two questions: 1) Is the influence of priors on gaze perception reduced as a function of autistic traits within a neurotypical population (Experiment 1)? 2) Do individuals with diagnosis of ASC show evidence for reduced influence of gaze priors (Experiment 2)? Each experiment began with a staircase procedure designed to tailor the noise contrast required for each participant to perform a left/right gaze discrimination at 80% correct. Participants were then required to judge the relative gaze directions of two faces when noise was added to the eyes of one face only. In Experiment 1, participants showed a significant bias towards perceiving uncertain gaze as direct, however this bias was not related to increasing autistic traits. In Experiment 2, individuals with ASC showed a robust direct gaze prior comparable to that of IQ matched controls. Given that noise-thresholds did not differ across groups, this finding is unlikely to reflect a combination of attenuated priors and increased sensory noise in ASC. These results pose a challenge to the hypoprior Bayesian model of ASC and suggest that if ASC is characterized by atypicalities in the use of prior information this is not reflected in their performance on a gaze task