Our brain sees what we expect, not what we see

Neuroscience have discovered that our perception of other people’s actions is heavily influenced by what we expect to happen, rather than what we actually see. Findings by a team of researchers at the Netherlands Institute for Neuroscience challenges previous assumptions about how our brains process social interactions and sheds light on the intricate communication between different brain regions.

For years, scientists have been studying how our brains interpret and understand the actions of others. It has been observed that when we watch someone perform an action, similar brain regions are activated as when we perform that action ourselves. This led researchers to believe that our brains follow a sequential flow of information: visual brain regions are activated first, followed by parietal and premotor regions that are responsible for executing similar actions. This sequential activation was thought to be the key to understanding what others do. However, these studies were limited to simple actions performed in isolation, not reflecting the complex nature of real-life social interactions.

To unravel the mysteries of our brain’s response to meaningful action sequences, a team of researchers led by Christian Keysers and Valeria Gazzola conducted an intriguing experiment. Collaborating with Jichi Medical University in Japan, the researchers had the unique opportunity to measure brain activity directly from epilepsy patients who were undergoing intracranial eeg-research. This technique allowed them to measure the brain’s electrical activity with unprecedented temporal and spatial accuracy.

During the experiment, participants watched a video showing various daily actions, such as preparing breakfast or folding a shirt. Electrodes implanted across the brain regions involved in action observation recorded their electrical brain activity, revealing how these regions communicate with each other. The video was shown in two different conditions: in one, the actions unfolded in their natural sequence, while in the other, the individual acts were randomly shuffled. The same actions were observed in both conditions, but only in the natural order did the participants’ brains utilize their knowledge of how they would perform these actions to predict what would happen next.

The results of the study, analyzed in collaboration with Pascal Fries of the Ernst Strüngmann Institute in Germany, were astonishing. When participants watched the reshuffled, unpredictable sequence, the brain exhibited the expected flow of information from visual regions to parietal and premotor regions. However, when viewing the natural sequences, the brain activity changed dramatically. The premotor regions, responsible for our own actions, communicated with the parietal cortex, suppressing activity in the visual cortex. As a result, participants seemed to see not with their eyes, but with their own expectations of how they would perform the actions.

By unraveling the complex interplay between different brain regions during action observation, this study opens up new avenues for studying cognitive processes and provides valuable insights into how our brains construct our perception of the world. 

This discovery aligns with a growing realisation in the neuroscience community: our brains are not simply passive receivers of sensory input. Instead, they are predictive organs, constantly anticipating what will happen next. As a consequence, expected sensory input is suppressed, allowing us to see the world from an internal perspective. However, when our expectations are violated, this suppression fails, and we become aware of what we actually see, rather than what we expected to see.