Additional experiments found that the effect of imagery on perception was approximately the same as showing the research subject a faint representation of one of the patterns between trials. Stronger shifts in perception were found if subjects either viewed or imagined a particular pattern for longer periods of time. They found that both imagery and perception can lead to a build-up of a "perceptual trace" that influences subsequent perception.
Pearson, Clifford and Tong also discovered that changing the orientation of the image from what had been imagined greatly reduced the impact of imagery on perception. Because orientation is processed in early visual areas, this suggests that imagery's interaction with perception may occur at early stages of visual processing.
The new findings offer an objective tool to assess the often-slippery concept of imagination.
"It has been very hard to pin down in the laboratory what exactly someone is experiencing when it comes to imagery, because it is so subjective," Tong said. "We found that the imagery effect, while found in all of our subjects, could differ a lot in strength across subjects. So this might give us a metric to measure the strength of mental imagery in individuals and how that imagery may influence perception."
The findings may also help settle a longstanding debate in the research community over whether mental imagery is visualthat one imagines something just as one sees itor more abstract.
"More recently, with advances in human brain imaging, we now know that when you imagine so
|Contact: Melanie Moran|