How the Brain Constructs Reality: Perception According to Neuroscience

How the Brain Constructs Reality: Perception According to Neuroscience

The world around us appears solid, coherent, and objective. But what if the reality we perceive is largely an internal construct of the brain? Contemporary neuroscience has shown that what we call "reality" is less a direct reflection of the external world and more an active interpretation , shaped by experience, expectation, memory, and emotion .

This article reveals how our brain constructs this “simulated reality” - and why understanding it can transform the way we live, decide, and relate.

The Brain Doesn't See: It Interprets

Although we have eyes, ears, skin, and other sensory pathways, it's our brain that truly "sees" the world. These organs capture physical stimuli (light, sound, pressure), but what we perceive only occurs after a process of neural interpretation .

For example:

• Light enters the eyes in the form of photons,

• The retina converts into electrical signals,

• The brain then reconstructs an image with depth, color and movement .

  
  

As neuroscientist David Eagleman explains:

“Our brain lives trapped in the dark, in the skull, interpreting electrical impulses without direct contact with the world.”

That is, we never see the world “as it is” - we see the world as our brain allows us to see it.

The Role of Prediction: Brain as Inference Engine

In recent years, the theory of the predictive brain , proposed by researchers such as Karl Friston , has gained traction. According to this view, the brain functions less as a reactive brain and more as a prediction machine , constantly trying to guess what's going on.

He compares what he expects with what he receives, and adjusts his perception accordingly.

"Perception is the brain's best guess about what is causing its sensory signals." – Karl Friston, 2010

This approach explains phenomena such as:

• Optical illusions (the brain fills in gaps with what it “thinks” is there),

• Déjà vu (when prediction precedes perception),

• Placebo and nocebo effects (in which expectation modifies actual bodily experience).

  
  

Fun Fact: Your Brain Slows You Down (On Purpose)

Research from the University of California revealed that the brain delays the formation of the image you see by about 80 milliseconds in order to gather more complete information.

In other words, the “now” that we perceive is already the past.

This invisible “editing” creates a continuous, fluid sense of reality—even as it is reconstructed in small pieces over time.

Perception and Emotion: Reality is Felt

The way we perceive reality is profoundly influenced by our emotional state. Studies in affective neuroscience, such as those by Antonio Damasio , show that:

• Emotions modulate attention,

• Emotions alter memory,

• Emotions define the value attributed to stimuli.

  
  

Therefore, two people in the same situation can have radically different perceptions. Reality is not absolute; it is interpreted through internal filters.

Everyday example:

• A sound can be interpreted as music by someone who is happy — or as noise by someone who is stressed.

• The same message can sound affectionate or hostile depending on the mood of the reader.

  
  

The Brain Simulates Before Acting

When performing any action, the brain simulates the consequences before acting. This occurs in the premotor cortex and executive planning areas , and is part of what enables us to act with intention.

In fact, the study of mirror neurons shows that simply observing an action activates motor regions in our brains as if we were actually performing the task. This has direct implications for empathy, imitative learning, and social relationships.

When Reality Fails: Hallucinations and Disorders

In some clinical conditions, such as schizophrenia or Charles Bonnet syndrome, the brain produces perceptions without external stimulation , reinforcing the idea that it is an active creator of reality.

"A hallucination is a perception without an external cause—but made by the same mechanisms as normal perception."– Oliver Sacks

These extreme cases help us understand that even what we consider real can be produced internally.

Final Reflection: Reality or Narrative?

Science shows that the brain doesn't seek absolute truth—it seeks coherence, predictability, and survival . This leads us to wonder: is reality truly objective? Or is it a biological and subjective narrative shaped to keep us alive?

Understanding how the brain constructs reality is liberating. It allows us to:

• Reduce perception conflicts,

• Understanding the role of empathy,

• Choose better the environments and stimuli with which we feed ourselves.

  
  

"Know thyself" can, in the 21st century, mean: understand how your brain manufactures your reality.