We are often unable to detect large permanent changes in a visual scene when they occur at the same time as a transient visual disruption. This "change blindness" has been studied in human psychophysics using visual transients like "mudsplashes" or blanks. Unfortunately, the tools available for exploring the neural basis of such phenomena in humans are limited. For study at the neuronal level, we need to observe change blindness in other species. In macaque monkeys, we impaired the ability to detect a change in direction of motion by accompanying the change with a brief visual transient. We were able to diminish the change-blindness by cueing the location of the change, indicating that the change was still visible. This could provide clues to the neural representation of visual scenes.

We assessed the monkey's ability to detect a change in direction of motion in a field of moving dots under several conditions. While the monkey fixated on a central point, several fields of drifting dots appeared. After a delay, the dots in one field changed direction. The monkey was rewarded for making an eye movement to the field that changed, or for maintaining fixation if no fields changed. In some trials, the change in direction was accompanied by a brief blank. The blank impaired the monkey's ability to detect even large changes in direction of motion. When the monkey was cued to the location of a potential change, he was once again able to detect changes in direction, presumably by focusing attention where the cue indicated.

Since the monkey was able to detect changes when cued, this suggests that change-blindness for motion was not due to interference with the visual system's ability to detect the change, but rather to a disruption of perceptual awareness of the change. This task provides a tool for the electrophysiological study of attentional mechanisms and the transformation of visual information from early processing to later perceptual levels.