Perception blindness, also called perceptual blindness or inattentional blindness, is a type of visual perception. It is a phenomenon in which people cannot see things in plain sight. The brain controls what is processed even though the eyes see the information. There are four factors that determine which visual information is processed by the brain and which information is discarded — conspicuity, workload, expectation, and capacity — and imbalance in any one of these can lead to perceptual blindness.
The senses of the human body are constantly gathering information. Unfortunately, not all of this information is processed for perception. This is because, although there is not a limit on incoming information, there is a limit on what the brain can process. For this reason, the brain uses four factors to determine which information gets processed. Perception blindness is likely to occur when any one of these factors is unbalanced.
Conspicuity is the first factor that influences perception. Sensory conspicuity is the brain's way of perceiving things based on colors and shapes, while cognitive conspicuity is the amount of relevance the brain gives to visual information. Both of these aspects can be manipulated by the brain. Certain information from the background can be discarded if it does not fit with the brain's goals of sensory or cognitive conspicuity, such as a specific flag blowing among several others or a person wearing a black shirt among many people wearing black and white shirts. These are instances of perception blindness.
Workload relates to the brain's workload. Perception blindness will occur more frequently while the brain is also trying to perform other tasks. Multitasking is common for many people, but performing two of the same types of perception tasks can reduce the amount of attention the brain provides. Two visual tasks, such as watching a bicyclist ride by and watching crosswalk signs, can cause a larger workload for the brain, which can lead to missing pieces of information.
Expectation and capacity are the final two factors that can influence perception blindness. People expect things to look a certain way, particularly if they have been the same for a while. If something changes, those objects can be overlooked. Capacity is the amount of attention each person can devote, and it varies depending on each person's mental ability to learn.
Preventing perception blindness involves multiple steps and a bit of time. Distractions from the task at hand should be minimized. Focusing on specific tasks one at a time should be practiced. Large tasks can be broken down into smaller ones. When working on long tasks, short breaks can help regroup thoughts and allow the brain a few minutes to rest.