On the different processing of wholes and parts: a psychophysiological analysis

The global precedence hypothesis (Navon, 1977) assumes that the processing of the global level of a hierarchical pattern precedes that of the local level. To explore further the nature of global and local processing of compound stimuli, we recorded the event-related brain potentials (ERPs) associated with ident@ing the global and local levels of nonlinguistic compound stimuli in a selective attention task. Wile subjects' behavioral responses were similar to those observed by Navon (1977), the analyses of ERP data showed that identification of the local level elicited longer N2 and P3 peak latencies with enhanced N2 and decreased P3 amplitudes relative to the identification of the global level. The inconsistency between the global and local levels made N2 and P3 amplitudes more negative with longer peak latencies. This interference effect on N2 and P3 amplitude and P3 latency was stronger on the local level than on the global level. The modulation of N2 by the consistency of the global and local levels observed in this and the previous (Heinze, Muente, et al., 1994) study suggests that the interference effect may be mediated by the early perceptual processing. Moreover, we found that the amplitude of an early posterior P1 component was modulated by attention to the global and local levels, being larger to the local target than to the global one. This PI effect gives no support to the notion that the variation of attentional spotlight determines the global precedence effect.