Better Visual Search in Infants At Risk for ASD

Background: Superior attention to details has frequently been described as a characteristic of ASD (Happe, 1999) and has been explained in terms of a diminished bias to attend to global structures or the semantic content of visual scenes (Happe & Frith, 2006). More recently it has become clear that superior perceptual abilities are not only measured in a situation of competition between local and global information processing. For example, children and toddlers with ASD were shown to be faster at detecting targets in visual search tasks (O’Riordan et al, 2001; Kaldy et al. 2011). However, these abilities may still be only a consequence of underdeveloped abilities to process or attend to higher-level information rather than their cause.  

Objectives: To investigate visual search abilities during the first year of life in children at-risk for ASD (owing to having an older sibling with this disorder). We want to determine whether superior visual search is measurable before a bias to attend to attend to global versus local information is established.  

Methods: Twenty-five low-risk participants (LR) and 35 high-risk participants (HR) took part in an eye-tracking (Tobii) study at 8 and 14 months of age. Participants saw circular displays of 1 target and 7 distractors, all letters (app. 9^ofrom the centre of the screen). Targets were either visually Similar to the distractors (a “V” or “+” target was presented together with 7 “X” distractors) or Dissimilar (an “S” or an “O”).  Stimuli were presented for 1.5 seconds. We measured the percentage of trials in which a fixation on a target was made. At 24 months we measured the ability to integrate local information into a global percept, by measuring recognition of textured silhouettes. 

Results: At 8 months only an effect of Trial type was observed, participants performing better in the Dissimilar target condition. At 14 months the high-risk group performed better than the low-risk group for both Trial types (no significant interaction between Group and Target type). The ten highest scores belonged to HR infants. Number of fixations before reaching the target and fixation duration on the target will also be analysed, as well as the relationship between visual search abilities and silhouette recognition. 

Conclusions: Better visual search (measured as a greater proportion of trials with target fixations) was observed in high-risk infants at 14 months of age. This replicates findings in toddlers with ASD (Kaldy et al, 2011) and extends those findings by demonstrating an earlier onset of perceptual differences. This is consistent with perceptual differences preceding and possibly driving later difficulties with global-level information processing (Happe, 2012). The lack of a differential effect of Trial type suggests that HR are not necessarily better at discriminating targets from distractors but that they are more willing to orient to these odd-one-out stimuli. This is in line with previous talks in this symposium showing faster orienting in high-risk infants.