Mixed lists of pictures and words (concrete nouns) were studied for a subsequent recognition task. In the recognition block, pictures and words designating previously studied pictures and words appeared in a completely crossed fashion, mixed with distractors. E.g. if a picture of a horse had been studied, either the picture or the word "horse" could appear in the test. Two groups of participants (12 persons in each) were given different instructions. In the exclusion group, instructions were to endorse as old only those items where format (picture/word) was preserved. In the inclusion group, instructions were to endorse both formats of a previously studied item. The purpose of this manipulation was to encourage a relative emphasis on perceptual characteristics in the exclusion group, and a predominance of conceptual encoding in the inclusion group. An added objective was to assess the extent to which the two stimulus formats invite perceptual or conceptual processing. Event-related potentials recorded during study were examined as to mean amplitudes in the 400-800 ms range. Amplitudes were higher for the exclusion group compared to the inclusion group over posterior areas, indicating perceptual processing. Conversely, the inclusion group exhibited higher amplitudes over frontal and temporal areas, indicating conceptual processing.