Enhancing and degrading visual stimuli

Several assembly language routines are described for use in perceptual identification experiments on the Apple Macintosh computer with MS-BASIC. These routines are in a machine language library that may be accessed from BASIC. No knowledge of assembly language is required to use the statements. In one method of perceptual identification, stimulus clarification, a mask is gradually removed to reveal the stimulus behind it. The other method, stimulus materialization, displays the stimulus on the screen in a piecemeal fashion. Data are reported from a demonstration experiment in which prior exposure to words enabled subjects to identify those words more easily under impoverished conditions.