Goal-based action generalization does not increase incrementally with action prevalence: Evidence from event-related...

Humans often rely on social group information to anticipate others' actions. While prior research suggests that group members' goals can be generalized to new individuals, it remains unclear whether this process scales incrementally with observed evidence or is constrained by prior beliefs. Across two experiments, we combined behavioral and EEG measures to examine whether the prevalence of observed actions enhances goal-directed actions generalization. In Experiment 1, participants observed animated groups performing goal-directed actions toward different targets while EEG was recorded. Both behavioral facilitation effects and contingent negative variation (CNV) amplitudes revealed stronger goal-based expectations for a group member when the group pursued a shared goal (i.e., high prevalence); medium and low prevalence conditions did not differ. Such a nongraded pattern indicates that statistical evidence is not the only factor shaping goal-based action generalization. In contrast, Experiment 2 showed that movement-based action generalization increases in a graded manner with action prevalence, highlighting the specific deviation from a graded pattern in goal-based action generalization. Together, these findings provide convergent behavioral and neural evidence that goal-based action generalization cannot be explained entirely by statistical evidence, but is instead constrained by shared-goal beliefs, underscoring the role of group-related beliefs in action prediction.