The effects of memory load and the contrast of the rod signal on partial report superiority in a Sperling task.

Subjects participated in a Sperling task. The independent variables included delay of report cue, dark background field vs. a light background field intense enough to nearly saturate the rod system (duration of rod icon), and whether or not subjects were required to retain a list of letters or words (memory load) while performing in the Sperling task. Partial report superiority is normally taken as an indication of iconic memory. However, the main result was that memory load, which presumably does not affect the duration of the icon, increased partial report superiority. The effect of luminance of the background field was to reduce the partial report superiority. The results show that the existence of a partial report superiority and/or a decaying partial report curve does not necessarily imply the existence of an icon or visual storage.