Individual Differences in Implicit Learning Abilities: Implications for Identifying Treatment Predictors

Background: Implicit associative learning is an individual’s ability to form connections between objects or stimuli without conscious awareness. These skills are critical for navigating the environment as well as higher order cognitive abilities and social communication and language skills.

Objectives: There is inconsistency in the literature as to whether individuals with ASD have difficulties with such learning. Some suggest that there is impairment, while others report no differences compared to typically developing individuals. It is likely that the discrepancy is not simply explained by methodological differences across studies, but reflects variability within ASD for implicit learning. We hypothesize that the children who do not respond to classic behavioral intervention have difficulties with implicit learning.

Methods: Building upon the extensive implicit learning literature, we designed a child-friendly task that measures differences in reaction time (RT) behavior and accuracy to a target stimulus predicted by two cues at differing probabilities. In each trial, children were instructed to touch a target image presented on an iPad but to refrain from touching the cues and distractor image. Unbeknownst to the participants, one of the cues predicted the target image at a high probability (75%), while the other cue preceded the target at a low probability (25%); the distractor appeared when the target was not presented. Trials were divided into thirds (early, middle and late) in order to assess learning differences.

Results: Preliminary results (N = 9; 2F; 3-6 years of age) are reported in typically developing (TD) children, typically developing children who have a sibling with ASD, and children with ASD. TD children demonstrated an increase in false alarms (incorrectly pressing the distractor) when presented with the high probability cue versus the low probability cue. TD children who have a sibling with ASD, and children with ASD, make an equal number of false alarms after the two cues. Regardless of diagnosis or sibling affiliation, all children show speeding in reaction times by the late trials to the target when preceded by the 75% cue compared to the 25% cue. Some children, regardless of age, demonstrate this pattern during early trials, suggesting individual differences in implicit learning.

Conclusions: Preliminary data suggest the ability to form associations during an implicit probabilistic learning task is variable in young children and may differ in the broader autism phenotype. Individual differences in how quickly children learn the patterns may be important for predicting intervention success in young children with ASD. Future testing in the three groups will further categorize individual variability in implicit learning abilities both within and across groups of children.