SAP - Sensation and Perception Module Overview

Sensation and Perception

At this very moment, you are bombarded with sensations. This text is in front of you. You can probably feel your chair against your back. You may be aware of the warmth or coolness of the air touching your skin. The odor of unwashed feet or your deodorant may have reached your nose. If you tried, you might be able to taste the flavor of the last food you ate still in your mouth! We understand the world by absorbing information through our senses. Psychophysicists study how people sense the external world through their sense organs and how they interpret those sensations and organize them into meaningful experiences. In this unit, you will learn how your senses work, why your interpretation of sensory information can sometimes be wrong, and why you don't always pay attention to the stimuli affecting your sense organs.

Essential Questions

How does top-down and bottom-up processing differ?
How does hearing work?
How does vision work?
What leads to hearing and vision loss?
How do visual illusions work?

Key Words

sensation - the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment
perception - the process of organizing and interpreting sensory information, allowing us to recognize meaningful objects and events
transduction - the conversion of environmental energy into neural signals
top-down processing - information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experiences and expectations
bottom-up processing - analysis that begins with the sensory receptors and works up to the brain's integration of sensory information
selective attention - the focusing conscious awareness on a particular stimulus
inattentional blindness - failing to see visible objects when our attention is directed elsewhere
absolute threshold - the minimum stimulation needed to detect a particular stimulus 50 percent of the time
audition - the sense or act of hearing
pitch - a tone's experienced highness or lowness; depends on the frequency
bones of the middle ear - these three tiny bones concentrate the vibrations of the eardrum on the cochlea's oval window
cochlea - a coiled, fluid-filled tube in the inner ear where hair cells vibrate to cause transduction
place theory - the theory that says the perception of pitch is caused by where the hair cells are vibrating in the cochlea
frequency theory - the theory that says the perception of pitch is caused by how quickly impulses travel up the auditory nerve
iris - the adjustable opening in the center of the eye through which light enters
pupil - a ring of muscle tissue that controls the size of the pupil opening; it forms the colored portion of the eye
lens - the transparent structure behind the pupil that changes shape to help focus images on the retina
accommodation - the process by which the eye's lens changes shape to focus near or far objects on the retina
retina - the light-sensitive inner surface of the eye containing the receptor rods and cones plus layers of neurons; where transduction occurs
fovea - the central focal point in the retina, where most of the eye's cones are located
rods - retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond
cones - retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions; the cones detect fine detail and give rise to color sensations
optic nerve - the nerve that carries neural impulses from the eye to the brain
nearsightedness - a condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina
farsightedness - a condition in which far-away objects are seen more clearly than near objects because the image of near objects is focused behind the retina
opponent-process theory - states that pairs of neural cells (red/green, blue/yellow, and black/white) create afterimages
trichromatic theory of vision - states that the retina contains red, green, and blue cones that can produce the perception of any color
shape constancy - perceiving objects as unchanging in shape, even as illumination changes
figure-ground - the organization of the visual field into objects and the background
size constancy - perceiving objects as unchanging size, even as retinal images change
visual capture - the dominance of vision over other senses
interposition - when a closer object blocks one's vision of an object that is further away
color constancy - perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

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