Abstract
The study examines whether A-prime is appropriate as an index of subjectively assessing imagery vividness. Half of the sixteen items in the Vividness of Visual Imagery Questionnaire (VVIQ) were used to generate visual images in a drawing-action condition with eyes closed, and the other half in an eye-movement condition with eyes opened. While the first condition enhanced the vividness of images, the latter reduced it. A-primes were computed on the assumption that vividness ratings of 1 (perfectly clear and as vivid as normal vision) and 2 (clear and reasonably vivid) can be regarded as a ‘hit' in the first condition and a ‘false alarm' in the second condition. A-prime predicted memory performance more accurately than the total VVIQ score. This result indicates that the new measure of A-prime has greater sensitivity in assessing imagery ability than the conventional measure of the total VVIQ score. Furthermore, A-prime did not correlate with the total score for the Mental Rotation Test, which is supposed to measure the inner scribe function that is responsible for image generation in visuo-spatial working memory. This result implies that imagery assessment and image generation are mutually independent.
