The effect of level of processing on perceptual and conceptual priming: Control versus closed-head-injured patients

Twenty-four closed-head-injured (CHI) and 24 control participants studied two word lists under shallow (i.e., nonsemantic) and deep (i.e., semantic) encoding conditions. They were then tested on free recall, perceptual priming (i.e., perceptual partial word identification) and conceptual priming (i.e., category production) tasks. Previous findings have demonstrated that memory in CHI is characterized by inefficient conceptual processing of information. It was thus hypothesized that the CHI participants would perform more poorly than the control participants on the explicit and on the conceptual priming tasks. On these tasks the CHI group was expected to benefit to a lesser degree from prior deep encoding, as compared to controls. The groups were not expected to significantly differ from each other on the perceptual priming task. Prior deep encoding was not expected to improve the perceptual priming performance of either group. All findings were as predicted, with the exception that a significant effect was not found between groups for deep encoding in the conceptual priming task. The results are discussed (1) in terms of their theoretical contribution in further validating the dissociation between perceptual and conceptual priming; and (2) in terms of the contribution in differentiating between amnesic and CHI patients. Conceptual priming is preserved in amnesics but not in CHI patients.