The retinal basis of iconic memory: Eriksen and Collins revisited.

The parameters of luminance, duration, wavelength, and interstimulus interval (ISI) were varied on the successive-field task first employed by Eriksen and Collins in 1967 and 1968. This task requires observers to combine visually the information presented in two brief successive presentations for successful trigram recognition. The results of the luminance and duration manipulations indicate that as stimulus energy is increased, iconic memory also increases. The wavelength and ISI manipulations reveal that performance at 20 msec ISI reflects cone (photopic) sensitivity but that performance at 250 msec ISI reflects rod (scotopic) sensitivity. These findings are interpreted in support of the retinal conception of iconic memory, with the cones providing a very transient icon and the rods providing the bulk of the persistence.