Sensory-dependent knowledge in young and elderly adults: arguments from the cross-modal priming effect

The nature of knowledge, i.e. sensory-dependent or abstract, is controversial. Growing evidence supports the existence of sensory-dependent knowledge in young individuals, but this question remains unexplored in elderly individuals. Thus the first objective of this study was to assess sensory-dependent knowledge in normal aging using a cross-modal priming paradigm. The cross-modal priming is a way to verify the nature of knowledge. However, contradictory results are reported about the existence of a cross-modal priming effect in normal aging. One possible explanation for the controversial findings is the priming task difficulty that would require too much executive resources in elderly participants and would prevent them to obtain a priming effect. Therefore, the second objective was to assess the executive involvement in the priming task. The method was based on a cross-modal priming paradigm with familiar bimodal items. First, all the sound primes were presented. For half of them, a visual abstract mask was presented simultaneously. Then, all the visual targets were processed. A battery of neuropsychological tests was administered to assess the involvement of executive functions in the priming paradigm. The results demonstrated a priming effect in the young and elderly participants, but only for the primes presented without the visual mask. The mask interference demonstrated the perceptual nature of the priming effect which supports the sensory-dependent theory of knowledge. The executive functions were correlated with the priming task only in the elderly participants. These results therefore support the task difficulty hypothesis.