Towards a Clarification of Attention to Faces in Atypical Development: Sustained Attention to the Face Is Task-Dependent in Autism Spectrum Disorder

Background: Humans present a strong face-orienting response and a visual preference for faces from birth. Consistent evidence indicates that defective attention to faces and other humans characterizes Autism Spectrum Disorder (ASD).

Objectives: In our eye-tracking study, we aimed to investigate the face-orienting response and the subsequent attentive selection, by analysing the proportion of first looks to the face and the sustained attention to faces, in a group with atypical and typical development.

Methods: 20 young adults with ASD (mean age: 22.1, standard deviation: 3.8; mean IQ: 118, standard deviation: 10) and 24 young adults with typical development (mean age: 22.4, standard deviation: 3; mean IQ: 122.4, standard deviation: 8.1) participated our eye-tracking study. Each participant received three types of instructions in random order at the beginning of each trial, and watched scenes of a social interaction between three actors on the eye-tracker screen. The instructions identified three experimental conditions: free-viewing (FV), visual-search (VS) - where participants were asked to find an object - and gaze-reading (GR) - where participants were asked to identify which actor was paying attention to the conversation. We analysed and compared the Proportion of First looks from the centre to the face and the Proportional Looking Time to faces in the two groups.

Results: We found that the Proportional Looking Time to faces differed across groups (FV: W = 87, p-value < 0.001; VS: W = 36, p-value < 0.001; GR: W = 113, p-value = 0.002), with minor proportion in the ASD group in all conditions. Furthermore, Proportional Looking Time to faces was task-dependent in the ASD group only, with maximum proportion in the GR and minimum proportion in the VS condition (FV vs VS: W = 157, p-value = 0.002, FV vs GR: W = 13, p-value < 0.001, VS vs GR: W = 13, p-value < 0.001). The same measure did not significantly vary across conditions in the typical group. The face-orienting tendency was above chance in all groups and did not differ across groups and conditions.

Conclusions: Participants with ASD varied the time allocated to faces in a social scene depending on the instruction. This result cannot be explained by a lack of an initial bias to orient to the face, since the face-orienting tendency was similar in the ASD and the control group. We interpret the results with a possible delayed disengagement of attention from the item that the task-at-hand explicitly emphasized in the scene. Our finding suggests that persons with ASD may end disregarding relevant environmental stimuli, when their attention is explicitly directed to a specific element.