A preliminary study of implicit statistical learning in non-clinical young adults exposed to early adversity.

Background: Early adversity is associated with long-term alterations in learning and decision-making under uncertainty, yet its impact on implicit predictive processing remains insufficiently characterized. This study investigated implicit statistical learning (ISL) in relation to exposure to adverse childhood experiences, operationalized using Childhood Trauma Questionnaire (CTQ) scores, in a non-clinical sample of young adults. Methods: Fifty-four participants were classified into High-CTQ and Low-CTQ groups and completed a visual ISL task in which stimulus predictability varied across conditions. Behavioral indices included reaction time and response accuracy as measures of sensitivity to probabilistic structure. Results: Both groups exhibited an implicit learning effect, indicated by faster responses in high- versus low-predictability conditions. However, this effect was attenuated in the High-CTQ group, suggesting reduced behavioral differentiation across probabilistic contingencies. Although the group × condition interaction for reaction time was not statistically significant, a significant main effect of group emerged for accuracy, with lower performance in the High-CTQ group, particularly in the low-predictability condition. In addition, individuals with higher CTQ scores subjectively reported perceiving stimulus sequences as more random despite equivalent task engagement across groups. Conclusions: These findings suggest that early adversity is associated with altered utilization of probabilistic environmental structure during statistical learning. Rather than reflecting a generalized deficit in learning or processing speed, the observed pattern indicates moderately reduced sensitivity to weaker predictive signals and a biased subjective representation of environmental randomness in the High-CTQ group.