Temporal integration in vision: Masking can aid detection

Temporal form-part integration is the process whereby two discrete sets of stimuli, presented at different times, are perceived by the visual system as a single integrated percept. Dixon and Di Lollo (Cognitive Psychology 26(1):33-63, 1994) proposed a temporal correlation model that was able to quantitatively account for a number of findings related to both form-part integration tasks and partial report. The present study demonstrates a novel approach to form-part integration—the addition of a whole-field mask stimulus at the termination of the second set of stimuli. According to an extension of the correlation model, the mask stimulus should reduce the visual system’s response to the trailing display, thus increasing the relative overlap of the two displays, fostering integration. Experiment 1 supported this hypothesis, showing a maximum benefit when the mask followed the trailing display immediately, as opposed to after a delay of 60 ms. Experiment 2 showed that this same mask actually did yield worse performance when presented immediately after a single set of stimuli. The third experiment collected detailed data for a few observers over a larger number of mask delays. Taken together, these experiments provide a rare example of masking degrading a target stimulus, and yet aiding perception.