Varieties of imagery and perception: the structure of task differences.

Introduction: This study assessed the dimensions and factors underlying visual mental imagery abilities in young healthy participants. A second purpose was to compare the underlying pattern of factors and dimensions in imagery with those in the corresponding perception tasks. Methods: We administered 15 tasks to 32 participants, assessing a wide range of imagery abilities, including imagery for faces, common objects, colors, words, mental rotation, scanning, image maintenance, auditory imagery, and tactile imagery. Response times and error rates were correlated for the imagery and for the perception tasks separately. The matrices were then analyzed using nonmetric multidimensional scaling and principal components analysis. Results: All analyses indicated the presence of two main clusters, one that appeared to correspond to tasks that draw on the object-properties "ventral system" and one that appeared to correspond to tasks that draw on the spatial-properties "dorsal system." Discussion: These results indicate a common segregation of the two major processing systems in visual imagery and visual perception.