Visualize the ball

Photo by Peter Werkman (http://​www​.peter​w​erkman​.nl/) via Flickr.

Visu­alize the ball.”

I’m sure most of you have heard the phrase at some point in your life — for me it was prob­ably as long ago as 9th grade gym class and had more to do with not get­ting hit by it than trying to catch it, but still — we’ve all heard the words.

And we might think that visu­al­izing an imag­i­nary ball would enhance our ability to see the actual ball once it’s headed our direc­tion. But research dating back to the early 20th cen­tury sug­gests the oppo­site. The Perky Effect, named for the man who coined it in 1910 (not some sprightly impact on one’s sen­si­bility), is the idea that imag­ined visual stimuli reduce a person’s ability to per­ceive real stimuli. “Having one inter­feres with the other,” said psy­chology pro­fessor Adam Reeves, who’s been trying to explain the process for more than two decades.

We have looked at the effects of color, of spa­tial ori­en­ta­tion, of spa­tial posi­tion, of pre­sen­ta­tion time, and of depth,” he said. “All with an idea as to locating the Perky effect in the visual brain.”

In an article recently pub­lished in Fron­tiers in Psy­chology, Reeves and his col­league at Eliz­a­beth­town Col­lege in Penn­syl­vania add a new twist to the story. “One might expect that increasing the amount of imagery would increase the inter­fer­ence,” said Reeves. “But the oppo­site hap­pens. Addi­tional ele­ments in the image ‘unmask’ the target, making it visible!”

So, how did they show this? First they had par­tic­i­pants imagine four ver­tical black lines. Then they briefly pre­sented them with an image of two real lines, stacked atop one another and slightly offset. The par­tic­i­pants had to keep their imag­i­nary lines in their field of vision and then report whether the lower line was set to the right or to the left of the top line in the real image (what I’ll call “the right/​left question”).

Two-​​line accu­racy tar­gets sur­rounded by imag­inery lines very close (ON), close or far away. Photo via Fron­tiers in Psychology.

When the imag­i­nary lines were very close to the real lines, par­tic­i­pants answered the left/​right ques­tion cor­rectly about 82% of the time. If the imag­ined lines were far away, they would answer were about 94% accurate.

Next, the team asked par­tic­i­pants to imagine eight lines instead of just four and repeated the same exper­i­ment. Instead of reducing accu­racy even fur­ther, the addi­tional ele­ments improved a participant’s ability to cor­rectly answer the right/​left ques­tion. This time, close imag­i­nary brought par­tic­i­pants’ accu­racy to 92%.

Prior to these results, Reeves’ team believed that the Perky Effect occurs because of feed­back mes­sages coming from the visual cortex (the part of the brain that stores an image) to the genic­u­late nucleus of the thal­amus, the point at which infor­ma­tion from the eye first reaches the brain. “The new ‘unmasking’ results chal­lenge this belief,” he said.

Half of the cells in the visual cortex project images for­ward to the next phys­i­o­log­ical unit in the brain. But the other half project back­wards to ear­lier stages of input, Reeves said. “So we know from the anatomy that feed­back is 50% of every­thing.” But why this hap­pens is still unclear. “Feed­back will be on the research horizon for the next few decades,” said Reeves. “Long after Catherine Lemley and I have retired!”