Researchers recently found that there is an area called thalamic pillow deep in the brain. It's like a receptionist for information. It is responsible for classifying and sorting out the information of external stimuli, and focuses people's attention on the most important information about behavior and survival. The researchers point out that the discovery is expected to lead to new treatments for disorders caused by lack of attention, such as attention deficit hyperactivity disorder, schizophrenia and so on.
The assumption that the brain cannot process too much information in detail at the same time, and only selectively focuses its attention on the things that are most relevant to behavior is made by the above argument.