Human perception requires sensory organs, the nervous system, and the brain to work together smoothly. Any breakdown in this system can prevent or change human perception of the world at large. The human brain is also limited in its ability to process information and takes certain shortcuts when processing the information that is received from the senses, especially during visual perception. Cultural conditioning and training also influence perception to some degree, as men and women are conditioned to regard certain stimuli as more important than others.
The human body's five senses collect an enormous amount of detail about the world. Each sensory system receives data from the world, whether in the form of light that strikes the rods and cones at the back of the eye or as vibrations in the air that are detected as sound by the ear. Once information has been received by a sense organ, it is passed along via nerves in the form of raw data. Damage to the nervous system can prevent information from ever reaching the brain for processing. The brain constructs a model of reality based on information received from the senses.
Each human being's sense organs have different strengths and weaknesses. The ability to collect raw data from the world imposes key limits on human perception. For example, as men and women age, most lose the ability to detect very high pitches. Many conditions can limit the ability of the senses to collect information from the world, and thus limit the brain's ability to perceive its surroundings.
Another factor that shapes human perception stems from the sheer volume of information that the senses are able to collect. The senses can potentially transmit far more raw information to the brain than the brain can actually process in a meaningful fashion. Parts of the brain work on a subconscious level to carry out raw processing and filtering in order to limit the conscious brain's attention to those pieces of information that are most relevant.
Typically, human brains follow certain patterns in sorting data. The brain is especially likely to notice changes. Motion in the field of vision, a rapid change in temperature, or the sudden sensation of an insect crawling on the skin are all likely to be passed on to the conscious brain. Certain men and women are naturally better at these perception tasks than are others, although conscious focus and training can improve anyone's abilities. Learned values also play a role in shaping perception, as cultural systems teach the conscious brain which pieces of information are significant, and memory and human perception can become interconnected.