Neural entrainment to visual rules in infant and adult brain.

Visual Rule Learning (RL) is a key cognitive ability allowing the detection and generalization of repetition-based rules in a continuous stream. Most studies on visual RL focus on post-exposure behavioral tasks, missing the learning process dynamics and the individual and age-related differences. Here, for the first time, we used neural entrainment to investigate visual RL, particularly in infants. Thirty adults and 27 nine-month-old infants were exposed to triplets of shapes in an ABA structure for 2 min while recording EEG. Triplets appeared at 6 Hz, with the embedded rule frequency at 2 Hz. Behavioral tests assessed rule discrimination between familiar (ABA) and novel patterns, measuring infants' looking behavior and adults' familiarity judgments. Results revealed a striking infant advantage: infants exhibited greater neural sensitivity to the rule frequency and a faster learning trajectory than adults. Adults showed stronger neural entrainment at the base frequency, particularly in frontal regions, reflecting developmental shifts in endogenous attention and salience processing. Importantly, in infants, neural response increased with repeated ABA exposure, correlating with successful rule discrimination, whereas adults showed no such progression. These findings provide the first evidence of an infant advantage in abstracting patterns from sensory input, supporting a general RL mechanism.