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Human perception: Our brain sees not what we see, but what we expect

In recent research conducted at the Netherlands Institute for Neuroscience, scientists have made a significant discovery about how our brains process social interactions, such as observing someone else’s actions. 

This study suggests that our perception is heavily influenced by our expectations, rather than solely by the visual information we receive.

Information processing 

Traditionally, it was believed that when we watch someone perform an action, our brain processes the information in a sequential manner. 

First, the visual regions of the brain are activated by seeing the action, followed by the activation of parietal and premotor regions involved in performing similar actions ourselves. 

This theory, based on studies where subjects observed isolated actions, like picking up a knife, presumed a direct flow of information from sight to action understanding.

Focus of the study

However, the new study challenges this notion about human perception. The research was led by Christian Keysers and Valeria Gazzola at the Netherlands Institute for Neuroscience, along with colleagues Chaoyi Qin, Frederic Michon, and collaborators from the Jichi Medical University in Japan.

The research involved epilepsy patients who participated in intracranial EEG research for medical purposes, providing a unique opportunity to measure brain activity with exceptional precision.

How the research was conducted

During the study, participants watched videos of everyday actions, such as making breakfast or folding clothes. The researchers tested two conditions: one where the actions were shown in their natural, predictable sequence, and another where the same actions were presented in a random order. 

This experimental design allowed the team to assess how brain regions involved in action observation communicate under different circumstances.

Critical insights 

The findings were groundbreaking. When actions were shown in a predictable sequence, the brain increasingly relied on its motor system to predict what would happen next. Essentially, what we expect to happen next shapes what our brain perceives. 

“What we would do next, becomes what our brain sees,” explained senior author Christian Keysers. This contrasts sharply with the classical model of information flow from visual to motor areas.

Seeing what we expect to see

This shift towards a predictive brain model indicates that our brains are not just passive receivers of sensory input. Instead, they actively generate predictions about what will happen next, and these expectations can suppress the actual sensory input. 

This phenomenon allows us to perceive the world as we expect it to be, unless our expectations are violated, prompting us to become aware of the actual sensory input.

Study implications 

The study’s findings contribute to a broader understanding within neuroscience about how our brains function. It suggests that we perceive and interact with the world based more on our internal expectations and predictions than on the external stimuli we encounter. 

This paradigm shift in understanding brain function and human perception opens up new avenues for exploring how we engage with the world around us.

The study is published in the journal Cell Reports.

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