The process by which stimulation of a sensory receptor produces neural impulses that the brain interprets as a sound, a visual image, an odor, a taste, a pain, or other sensory image. Sensation represents the first series of steps in processing of incoming information
A process that makes sensory patterns meaningful. It is perception that makes these words meaningful, rather than just a string of visual patterns. To make this happen, perception draws heavily on memory, motivation, emotion, and other psychological processes
Transformation of one form of energy into another - especially the transformation of stimulus information into nerve signals by the sense organs. Without transduction, ripe tomatoes would not appear red.
Loss of responsiveness in receptor cells after stimulation has remained unchanged for a while, as when a swimmer becomes adapted to the temperature of the water
The amount of stimulation necessary for a stimulus to be detected. In practice, this means that the presence or absence of a stimulus is detected correctly half the time over many trials
The smallest amount by which a stimulus can be changed and the difference be detected half the time
Just noticeable difference (JND)
Same as the difference threshold
(The smallest amount by which a stimulus can be changed and the difference be detected half the time)
The concept says that the size of a JND is proportional to the intensity of the stimulus; the JND is large when the stimulus intensity is high and small when the stimulus intensity is low.
Signal detection theory
Explains how we detect "signals," consisting of stimulation affecting our eyes, ears, nose, skin, and other sense organs. Signal detection theory says that sensation is a judgment the sensory system makes about incoming stimulation. Often, it occurs outside of consciousness. In contrast to older theories from psychophysics, signal detection theory takes observer characteristics into account
The thin light-sensitive layer at the back of the eyeball. the retina contains millions of photoreceptors and other nerve cells.
Light-sensitive cells (neurons) in the retina that convert light energy to neural impulses. The photoreceptors are as far as light gets into the visual system
Photoreceptors in the retina that are especially senstive to dim light but not to colors. Strange as it may seem, they are rod-shaped
Photoreceptors in the retina that are especially sensitive to colors but not to dim light. They are cone-shaped.
The point where the optic nerve exits the eye and where there are no photoreceptors. Any stimulus that falls on this area cannot be seen
Also called hue; not a property of things in the external world. Rather, it is a psychological sensation created in the brain from information obtained by the eyes from the wavelengths of visible light
The entire range of electromagnetic energy, including radio waves, X rays, microwaves, and visible light
The tiny part of the electromagnetic spectrum to which our eyes are sensitive. The visible spectrum of other creatures may be slightly different from our own
The idea that colors are sensed by three different types of cones sensitive to light in the red, blue, and green wavelengths. The trichromatic theory explains the earliest stage of color sensation.
The idea that cells in the visual system process colors in complementary pairs, such as red or green or as yellow or blue. The opponent-process theory explains color sensation from the bipolar cells onward in the visual system.
sensations that linger after the stimulus is removed. Most visual afterimages are negative afterimages, which appear in reversed colors.
Typically a genetic disorder (although sometimes the result of trauma) that prevents an individual from discriminating certain colors. The most common form is red-green color blindness.
The physical strength of a wave. This is usually measured from peak (top) to valley (bottom) on a graph of the wave
The primary organ of hearing, a coiled tube in the inner ear, where sound waves are transduced into nerve messages
A thin strop of tissue sensitve to vibrations in the cochlea. The basilar membrane contains hair cells connected to neurons. When a sound wave causes the hair cells to vibrate, the associated neurons become excited. As a result, the sound waves are converted (transduced) into nerve activity
the quality of a sound wave that derives from the wave's complexity (combination of pure tones). Timbre comes from the Greek word for "drum," as does the term tympanic membrane, or eardrum.
The sense of body orientation with respect to gravity. The vestibular sense is closely associated with the inner ear and, in fact, is carried to the brain on a branch of auditory nerve
the sense of body position and movement of body parts relative to each other (also called kinesthesis)
Chemical signals released by organisms to communicated with other members of their species. Pheromones are often used by animals as sexual attractants. It is unclear whether or not humans employ pheromones
An explanation for pain control that proposes we have a neural "gate" that can, under some circumstances, block incoming pain signals
A response to a placebo (a fake drug), caused by subjects' belief that they are taking real drugs
The meaningful product of perception - often an image that has been associated with concepts, memories of events, emotions, and motives
Refers to the process used by the brain to combine (or "bind") the results of many sensory operations into a single percept. This occurs, for example, when sensations of color, shape, boundary, and texture are combined to produce the percept of a person's face. No one knows exactly how the brain does this. Thus, the binding problems is one of the major unsolved mysteries in psychology
Perceptual analysis that emphasizes characteristics of the stimulus, rather than our concepts and expectations. "Bottom" refers to the stimulus, which occurs at steop one of perceptual processing.
Perceptual analysis that emphasizes the perceiver's expectations, concept memories, and other cognitive factors, rather than being driven by the characteristics of the stimulus. "Top" refers to a mental set in the brain - which stands at the "top" of the perceptual processing system
The ability to recognize the same object as remaining "constant" under different conditions, such as changes in illuminations, distance, or location
You have experienced an illusion when you have a demonstrably incorrect perception of a stimulus pattern, especially one which also fools others who are observing the same stimulus. (If no one else sees it the way you do, you could be having a delusion or a hallucination. We'll take those terms up in a later chapter on mental disorder.)
Images that are capable of more than one interpretation. There is no "right" way to see an ambiguous figure.
From a German word that means "whole" or "form" or "configuration." The Gestalt psychologists believed that much of perception is shaped by innate factors built into the brain
The Gestalt principle that identifies the tendency to fill in gaps in figures and to see incomplete figures as complete
Laws of perceptual grouping
The Gestalt principles of similarity, proximity, continuity, and common fate. These "laws" suggest how our brains prefer to group stimulus elements together to form a percept
Law of similarity
The Gestalt principle that we tend to group similar objects together in our perceptions
Law of proximity
The Gestalt principle that we tend to group objects together when they are near each other.
law of continuity
The Gestalt principle that we prefer perceptions of connected and continuous figures to disconnected and disjointed ones
Law of common fate
The Gestalt principle that we tend to group similar objects together that share a common motion or destination
Law of Praganz
The most general Gestalt principle, which states that the simplest organization, requiring the least cognitive effort, will emerge as the figure. Proganz shares a common root with pregnant, and so it carries the idea of a "fully developed figure."
information taken in by both eyes that aids in depth perception, including binocular convergence and retinal disparity
information about depth that relies on the input of just one eye - includes relative size, light and shadow, interposition, relative motion, and atmospheric perspective
The view that perception is primarily shaped by learning (or experience), rather than by innate factors