The way a person experiences the world depends directly on the processes of sensation and perception. Sensation is the process whereby a stimulus in the environment is detected by the body and converted into neural signals, or chemical and electrical signals sent to the brain via neurons. Perception is the way the brain interprets or understands that neural signal. Put another way, sensation is a bottom-up process—information processing begins with the reception of stimuli and ends with interpretation by the brain. Real-world information stimulates the senses. Perception is a top-down process—it is constructed in the mind from experience and expectations, and meaning is imposed on sensation. Combined, the study of sensation and perception provides insight into how people make sense of the world around them. Humans have five major senses (sight, hearing, touch, taste, and smell). They also have vestibular sense—the sense that provides information about movement, balance, and equilibrium—and proprioception—the sense of where one's body parts are in relation to other body parts.
At A Glance
- Sense organs receive sensory stimulation, convert it into neural activity, and deliver it to the brain.
- The brain processes inputs from all senses simultaneously. Aspects of both the stimuli and the perceiver can affect how sensory information is interpreted.
- In vision, the lens of the eye focuses light on the retina. Rods, cones, and other retinal cells transmit information along the optic nerve to the brain.
- Different wavelengths of light are processed by cone receptor cells in the eye. The brain processes the pattern of signals received from the cones, resulting in color perception.
- In the brain the thalamus relays information from the optic nerve to the parietal and temporal lobes, where it is interpreted as color, movement, size, distance, or boundaries.
Sound waves are sensed by hair cells in the organ of Corti, which transmit sound frequency and intensity information to the auditory cortex.
- Hair cells in the ear allow detection of sound volume and pitch (the perception of sound as high or low). Slight variations in when sound waves reach each ear help the brain determine the location of the sound.
Tongue receptors detect sweet, sour, salty, bitter, and umami (savory) tastes and may also detect fat and starch.
Olfactory receptors each detect a specific odorant, or chemical odor. Smell plays a significant role in taste and helps protect against eating spoiled food.
- The somatosensory system detects bodily sensations such as temperature, pressure, and pain. Pain perception includes emotional components and does not align perfectly with sensory inputs.
Proprioception indicates the body's position and orientation in space. The vestibular sense maintains balance and equilibrium.
Subliminal information is processed by the brain outside of conscious awareness. In some limited situations subliminal information may influence attitudes, preferences, or behaviors.
- Some people believe in extrasensory perception (ESP), the ability to perceive information undetectable by the five senses, but evidence for ESP has not been demonstrated in well-designed studies.