Rod Persistence on a Partial-Report Task with Scotopic and Photopic Backgrounds

Abstract

Two experiments were undertaken to demonstrate the participation of the rod system under certain stimulus conditions on the partial-report task of iconic memory. In Experiment 1, scotopically matched letter arrays of differing wavelength produced equivalent partial-report superiority but only if relatively large letters and a long cue delay were employed. In Experiment 2, variable photopic backgrounds were employed in contrast to the constant dark background used in the first experiment. For constant luminance targets, photopically matched red and blue-green backgrounds of 5 ftL (15.9 cd/m2) did not produce equivalent partial-report performance. Partial-report superiority was evident at much longer cue delays with the red background. This was attributed to the minimal stimulation of the rod system by this long wavelength background. However, if an intense adaptation field that saturated the rod system were interposed between stimulus trials, the photopically matched backgrounds then produced equivalent partial-report performance at all cue delays.