Emotional consistency guides social engagement in 18- to 24-month-old toddlers.

This study investigated toddlers' sensitivity to emotional consistency and its influence on social engagement. Sixty-eight toddlers of diverse ethnic backgrounds (39 females; 338-908 days old; 79.4% White; and collected in 2024) watched videos depicting adults expressing emotions toward novel objects. The expression valence was either consistent (e.g., always positive toward Object A) or inconsistent (e.g., both positive and negative toward Object A). Eighteen- to 24-month-olds exhibited distinct looking when learning the consistent versus inconsistent informants (Cohen's d = 0.42) and showed greater sustained gaze following toward the emotionally consistent informants (Hedges' g = 0.45). Twelve- to 18-month-olds did not differentiate between conditions. These data suggest that detecting and utilizing emotional consistency as a cue for social engagement develops during the second year of life.