Voluntary control of reversible figures.

This study was designed to demonstrate that voluntary control of the perception of reversible figures is possible. Within the context of a fully counterbalanced design, some subjects were given instructions as to which side of a reversible screen or staircase to keep closer while others served as no instruction controls. As predicted, voluntary control was clearly demonstrated over both figures. Voluntary control instructions did not influence the frequency of reversals directly, but frequency of reversals and voluntary control were inversely related. Moreover, subjects' voluntary control over one figure was highly correlated with their control over the other, suggesting the presence of stable individual differences in ability to control perception voluntarily.