how our brains notice when something has changed?

Question

For example, if I go into my room and something is moved, my brain will unconsciously realize and bring it into conscious awareness that something has changed. How does the brain detect these changes and decide it’s important enough to bring to awareness? What processes are happening when we notice changes?

In: 15

Answer 1

I have an amateur interest in cognitive neuroscience, and I’m not a professional, so bear that in mind.

Both consciously and subconsciously, and over short and long time scales, your brain acquires “mental models” of the world and how it is expected to work. Models for things like how objects will behave if dropped (they will fall straight down until they hit something), how people will act in certain situations (they will get upset if you hit them), how things will feel if you touch them (sharp edges will cut you), etc.

Your brain takes the sensory input from eyes, ears, etc and combines it with these mental models to make predictions about what sensory input it might expect in the future. This happens continuously every waking moment and mostly without you even realizing it.

Your brain compares its past predictions with its current sensory input for differences, called prediction errors. If the error is large enough, our attention is drawn towards that input. Error indicates that something has changed and we may need to take action, or maybe just update our mental models to make more accurate predictions in the future.

This is why magic shows are so captivating. They are designed to cause large prediction errors by violating our mental models, and cause us to feel a sense of amazement and wonder “how did they do that!?”.

Psychosis in schizophrenia is hypothesized by some to be the result of a disruption in this process. If the brain erroneously decides a certain stimulus violates its mental models, it can be interpreted in odd ways and lead to their mental models becoming “corrupted.” E.g. A schizophrenic person observes the ordinary sight of two strangers talking in the park, falsely determines this has some special meaning relevant to him, and comes to believe that they are secretly talking about him.