Different parts of our brain are responsible for different things. One part is mostly in charge of memory, while another part may be more important on the auditory front. An entirely different area, meanwhile, may be responsible for unconscious actions like our heartbeat. Vision is no different; it’s associated with the aptly named visual cortex, which is situated in the back of the brain. But it turns out we may not be giving this area of the brain the credit it deserves, as it may be able to make decisions, just like other traditionally “higher level” brain areas, according to a new study.

Cognitive psychology is still a relatively new discipline, and these findings provide another clue to how exactly our brains work. “As a field, we’re only at the beginning of trying to figure out how the brain works, and the visual system is a very good place to start,” said Jan Brascamp, Michigan State University professor and lead investigator of the study in a press release. “In that light, the current findings, which show that the visual system has a capacity we previously didn’t expect, are an important step in the right direction.”

The experiment placed participants in an MRI scanner, and had them view two adjacent dot patterns on a projection screen. Researchers used a set of prisms to be sure that the participant’s eyes were each focused on a different pattern, making it very different from a normal visual situation. Brain activity was monitored throughout.

By having each eye focus on a different pattern, the researchers created an optical illusion in which the participants’ perceptions would switch between the two patterns. Their eyes were providing contradictory information, so their brains tried their best to make sense of it. In past MRI studies on switching perceptions, the association cortex — known for high-functioning decision making — was deemed the controller, and the visual cortex was thought to only handle the processing of visual information.

The difference between these experiments and Brascamp’s was that in past studies, participants could consciously tell when their perception changed because the illusion was obvious. For example, the famous duck-rabbit image causes a noticeable change in perception because a person can explain that they see either a duck or a rabbit when it becomes apparent to them. This often caused surprise, and the areas of the brain involved in decision making are very similar to those involved with surprise.

Brascamp and his team took away this surprise by making sure study participants were unaware of their changing perceptions — they didn’t even know the two patterns of dots were different. They didn’t notice their perception going back and forth between two patterns either and, among these participants, brain activity in the association cortex was gone. This led to the conclusion that the visual cortex was making the choice on its own.

“That is one sense in which our study is counterintuitive and surprising,” Brascamp said. “The part of the brain that is responsible for seeing, for the apparently ‘simple’ act of generating the picture in our mind’s eye, turns out to have the ability to do something akin to choosing, as it actively switches between different interpretations of the visual input without any help from traditional ‘higher level’ areas of the brain.”

Source: Brascamp J, Blake R, Knapen T. Negligible fronto-parietal BOLD activity accompanying unreportable switches in bistable perception. Nature Neuroscience. 2015.