Imaging goal-directed movement

The main purpose of the present investigation was to determine how Shepard's (1968) second-order isomorphic principle relates to imaging goal-directed movement. Reports of movement times for actual and imaged movements were obtained using Fitts-type tapping tasks. Displays consisted of two different (referential) or two identical (nonreferential) stimulus pairs. In Experiments 1a and 1b, target width and amplitude were manipulated to produce two indexes of difficulty. In Experiments 2a and 2b, the index of difficulty was constant, and biases were created by indicating that movement time increased with decreases in target width or increases in amplitude. In all four experiments, reported movement time reflected Fitts' (1954) law for actual tapping and during early trials for referential imagery. In Experiments 1a and 1b, reported movement times for the two indexes of difficulty were similar for nonreferential imagery and at later trials for referential imagery. In Experiments 2a and 2b, reported movement times reflected the biases for nonreferential imagery and at later trials for referential imagery. The results suggest that propositional knowledge and information processing interact to control movement imagery.