Hierarchical processing and level-repetition effect as indexed by early brain potentials.

Event-related potentials were recorded to investigate the mechanisms of hierarchical processing and level-repetition effect. Participants identified targets that appeared at global, local, or both levels of hierarchical patterns. Reaction times showed global precedence and level-repetition effects. An occipital P1 wave was enhanced to local relative to global targets. The P1 to local targets was also larger when preceded by global than local targets. Global and both-level target selections were indexed by two posterior negativities peaking at 130 and 190 ms poststimulus, whereas local target selection was indexed by a broad occipitotemporal negativity. A late selection positivity was observed over the left occipitotemporal site for global targets but over the central site for local targets. The findings suggest that sensory-perceptual mechanisms contribute to global precedence and level-repetition effects in hierarchical processing.