In memory retrieval, search can be guided by mental sets towards different subsets of the available evidence. Such retrieval orientations have been suggested to leave an imprint on event-related potentials (ERPs). The present study aimed at characterizing orientations towards perceptual and conceptual evidence in a recognition task, where pictures and words were studied. In the recognition test, items were presented in either the same format as at study or in the opposite format. A between-subjects manipulation modified the task, instructing an Exclusion group to endorse only items that preserved their format from study, and an Inclusion group to endorse both formats of a studied item. It was hypothesized that exclusion instructions would instil a perceptual - and inclusion instructions a conceptual - orientation. As a corollary, instructions were expected to dissociate the high end from the low end of the picture-word mirror effect. This expectation was confirmed in a behavioural experiment. In an ERP experiment, retrieval orientations were examined in their effects on correct rejections of new pictures and words. Confirming earlier findings (Hornberger, Morcom, & Rugg, 2004), a perceptual orientation was accompanied by more positive-going amplitudes over widespread areas. The difference was larger for pictures than for words, supporting behavioural evidence that new pictures are more easily rejected on perceptual grounds than are new words. The Exclusion group showed no ERP evidence of cross-format old-new effects, despite reaction times indicative of involuntary conceptual recognition. The results indicate that perceptual and conceptual retrieval orientations imprint distinct signatures on ERPs. They further suggest that the examined old-new effects in ERPs are mainly linked to voluntary aspects of memory, even in a task where involuntary memory exerts effects on reaction times.
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