An ERP indicator of processing relevant gestalts in masked priming.

Briefly presented arrows, made indistinguishable by masks that contain arrows, inversely prime responses to following visible arrows. This inverse effect might reflect general regularities of masked priming or be either due to the task-relevant elements of the mask or to special features of arrows. Here we report a slow negative EEG potential recorded from the scalp above the visual cortex, which is evoked by masks that contain arrows. Even being evoked when arrows masks were presented in isolation, this "Nd-mask" appeared to be an obligatory response. Yet Nd-mask was enhanced when primes and targets were arrows and was reduced in the other cases, and even reversed its polarity with appropriate control stimuli. These findings provide support both for the special status of arrows and for the notion of mask relevance. Nd-mask might be one instance of negative EEG potentials evoked by stimuli with familiar gestalts.