Investigating Semantic Integration of Gestures with Nouns in Neurodiverse Individuals via Event Related Potentials

Iconic hand gestures paired with speech can enhance word comprehension and are candidates for caregiver delivered interventions in rural settings where access to language services is limited. Whether children’s brains process gestures as communicative semantic content, and whether this differs between typically developing and neurodivergent children, is not well characterized. We recorded 20 channel EEG at 500 Hz from 13 participants across four groups (typically developing four year olds, typically developing older children, older neurodivergent children with ASD, ADHD, or both, and adults) during a passive viewing trifecta paradigm in which each spoken noun appeared with a matching or mismatching animation (Time 0) or iconic gesture (Time 1). After FASTER style preprocessing and epoching time-locked to the final target stimulus of each trial, we examined the N400 response over an eight channel centro-parietal and temporal region of interest. In Gesture word last trials, match and mismatch waveforms diverged approximately 300 ms after speech onset with the expected direction in typically developing older children (d = 0.34), neurodivergent older children (d = 0.78), and typical four year olds (d = 0.36), suggesting that gesture and speech pairings yielded the most consistent semantic differentiation across groups, evidence for semantic processing and integration; the largest single effect was observed for Animation in four year olds (d = 1.80). Animation last and gesture last trials did not show the same canonical pattern. Per word amplitudes in the N400 time window identified Goat, Umbrella, and Emoji as more stable items and Lock, Flag, and Rectangle as more variable. These preliminary findings from eight participants and 251 retained epochs support the trifecta paradigm for studying gesture and speech integration across development and motivate larger studies with normed stimuli.