An Investigation of Social-Perception Strategies in the Broad Autism Phenotype: Integrating Eye Tracking and Behavioral Methodologies

Background: The Broad Autism Phenotype (BAP) is a cluster of social, language, and personality features representing subtle expressions of autism characteristics, found in non-autistic relatives of individuals with autism (Pickles et al., 2000).  Social features of the BAP are related to deficits in social-cognition (Losh & Piven, 2007), though the neurocognitive mechanisms underlying these traits are not fully understood.  Investigation of perceptual strategies during social-cognitive tasks may further clarify underlying neurocognitive mechanisms. Existing eye tracking studies of individuals with autism describe atypical fixation patterns when processing social stimuli. In contrast to controls, who focus mainly on the eyes, individuals with autism fixate on less salient regions, such as mouths, bodies, and objects (Klin et al., 2000). Similar patterns have been noted in the BAP (Adolphs et al., 2008); however, investigation of fixation patterns during a variety of social-cognitive tasks is needed to clarify these patterns and detect links to underlying neurocognitive mechanisms.   
Objectives: This study employs eye tracking to investigate the relationship between face scanning strategies and behavioral responses during a social-cognitive task with established ties to discrete brain regions, and the amygdala in particular.  For this study, a sample of BAP+ parents was selected from a previous study based on severely aberrant social-cognitive performance, with the goal of investigating further the underlying features of their unique profile.
Methods: Five BAP+ parents of children with autism were tested [with additional data collection underway (target BAP+  n=15, Control n= 15)]. Clinical characteristics of the BAP were assessed using established, valid and reliable tools for discriminating parents of individuals with autism from controls.  Behavioral data were collected using the social-cognitive task, ‘Trustworthiness of Faces’, which requires evaluation of 42 faces varying in hedonic tone for trustworthiness cues. Tobii 1750 equipment captured eye tracking data during this task to discern processing strategies through comparison of fixation patterns to behavioral responses.
Results: In contrast to typical scan patterns described in the literature, showing primary fixation on the eyes (Walker-Smith et al., 1977), BAP+ participants focused preferentially on the nose, with only slightly greater fixation on the right eye. In positively-normed (i.e., “friendly”) slides, subjects looked substantially more at noses than mouths, despite the informative nature of smiles in these slides. Analyses of fixation patterns in relation to ratings of trustworthiness revealed that BAP+  participants assigned negative ratings to both positive (i.e. trustworthy) and negative (i.e. not trustworthy) faces, compared to norms.  
Conclusions: Preliminary eye tracking data implicate perceptual processing strategies that may elucidate the basis of the mild social-cognitive impairments previously documented among autism parents who demonstrate the social features of the BAP.  In particular, the tendency of the BAP group to rate all faces, both positive and negative, as untrustworthy, coupled with the atypical fixation on non-salient facial features (i.e., noses), suggests that aberrant facial scanning strategies affect interpretation and judgment of social information.