Searching for an object is obviously easier if you know what the object looks like. But knowing what not to look for can also speed up your search, and make it more efficient too, according to new research from Johns Hopkins University.

"Individuals who explicitly ignore distracting information improve their visual search performance, a critical skill for professional searchers, like radiologists and airport baggage screeners," said lead author Corbin A. Cunningham, a graduate student in the Krieger School of Arts and Sciences' Attention and Perception Lab, in a press release. "This work has the potential to help occupations that rely on visual search by informing future training programs."

The study, published in Psychological Science, used two experiments to find out how the brain processes complex information. In one, 26 participants were asked to look for capital letters “B” or “F” among four letters of different colors, all of which surrounded a cross. The researchers also included lower case versions of the two letters to throw off the participants. For some, the letters appeared in random different colors. Others, meanwhile, were told to ignore one specific letter, which appeared in the same color, while all other letters appeared in random colors.

Participants’ search time was initially slow when they were told to ignore letters in these specific colors. However, over the course of 100 tests, they eventually became better at finding the letters than those who had no letter clues at all. This suggested to the researchers that people are more efficient searchers when they know what to ignore.

Image Search Would have been able to find the T faster without knowing it wasn't red? Research says no. Corbin A. Cunningham/JHU

The second experiment brought together 52 people for similar tasks. This time, however, participants were given 12 letters to serve as distractions instead of four, and the color schemes were changed. In one trial, half of the letters were the same color while the others varied — “B” or “F” could have been any one of the colors. In the other, all of the majority colors were the same, while the others varied. Again, participants took some time to learn, but once they did, they could quickly identify the “B” or “F.” The more information they ignored, the better they were at finding the letters.

The researchers consider a person’s ability to ignore information to be key to their attentional capacity. Co-author Howard Egeth, a professor of psychological and brain sciences at Johns Hopkins, said this study, as well as one that tracked brain activity during similar tasks, shines light on the importance of ignoring other stimuli when searching for a specific object — something Egeth calls the “dark side of attention.”

Source: Cunningham C, Egeth H. Taming the White Bear: Initial Costs and Eventual Benefits of Distractor Inhibition. Psychological Science. 2016.