By peace | January 2, 2007
Much of our knowledge begins as sensation. Information about physical changes is received by sensory neurons, transmitted to the brain, and interpreted or perceived. Each sensory system is structured to receive a particular form of physical energy and convert it into neural impulses to the brain.
The visual system processes light information, which is focused by the cornea and lens, received by light sensitive neurons in the retina called rods and cones, and transmitted to the brain via the optic nerve.
The process of audition or hearing involves translating sound — a form of mechanical energy — into neural energy. They qualities of sound amplitude and frequency are translated into the experiences of loudness and pitch. Both qualities are funneled via vibrations through the outer ear, along the structures of the middle ear, and to the vibration-sensitive hair cells in the inner ear. These specialized neurons transmit impulses along the auditory nerve to the brain.
Other senses studied included the vestibular sense or sense of balance; the skin senses, including touch and proprioception; gustation or taste; and olfaction or smell.
Whereas sensation involves mere awareness that a sensory system has been activated, perception requires interpretation or recognition of sensory information. Early structuralists focused on sensory consciousness by means of introspection. Psychophysicists studied the relationships between physical stimili and psychological perceptions. Early psychophysics emphasized a threshold approach to understanding the detection of stimuli and stimulus changes. More recent psychophysical work favours signal detection theory, which characterizes perception as a decision-making process in which signals must be detected against a background of noise.
Gestalt principles of perception emphasize the importance of meaning in human perception. Gestalt psychologists have identified such principles as figure-ground relationships, closure and grouping principles.
A well-studied phenomenon is depth perception, including both monocular and binocular cues. Research examines the contributions to depth perception made by innate abilities and cultural experiences.
The brain is able to identify constancies across perceptual impressions although images are constantly changing and varied. Illusions, or erroneous perceptions, involve interactions between visual cues, as well as some experience effects.
The cognitive approach characterizes human perception as information processing, involving the bottom-up sequence of interpreting sensations as well as the top-down process of narrowing the perceptual search according to expectations and meaningful experiences. An interactive model, combining features of both these processes, preserves an understanding of human perception as dynamic, flexible and meaning-seeking.