Sensation and Perception Rapid Review for AP Psychology
A more in-depth study guide for this review can be found at:
Sensation—the process by which you detect physical energy from your environment and encode it as neural signals.
Psychophysics—the study of the relationship between physical energy and psychological experiences.
Stimulus—a change in the environment that can be detected by sensory receptors.
Absolute threshold—the weakest level of a stimulus that can be correctly detected at least half the time.
Signal detection theory—maintains that minimum threshold varies with fatigue, attention, expectations, motivation, emotional distress, and from one person to another.
Difference threshold—minimum difference between any two stimuli that a person can detect 50% of the time.
Just noticeable difference (jnd)—experience of the difference threshold.
Weber's law—difference thresholds increase in proportion to the size of the stimulus.
Subliminal stimulation—receiving messages below one's absolute threshold for conscious awareness.
Transduction—transformation of stimulus energy to the electrochemical energy of neural impulses.
Perception—the process of selecting, organizing, and interpreting sensations, enabling you to recognize meaningful objects and events.
Vision and the human eye:
Rays of light from an object pass from the object through your cornea, aqueous humor, pupil, lens, and vitreous humor before forming an image on your retina.
Cornea—transparent, curved layer in the front of the eye that bends incoming light rays.
Iris—colored muscle surrounding the pupil that regulates the size of the pupil opening.
Pupil—small adjustable opening in the iris that is smaller in bright light and larger in darkness.
Lens—structure behind the pupil that changes shape, becoming more spherical or flatter to focus incoming rays into an image on the light-sensitive retina.
Accommodation—process of changing the curvature of the lens to focus light rays on the retina.
Retina—light-sensitive surface in the back of the eye containing rods and cones that transduce light energy. Also has layers of bipolar cells and ganglion cells that transmit visual information to the brain.
Fovea—small area of the retina in the most direct line of sight where cones are most concentrated for highest visual acuity in bright light.
Photoreceptors—modified neurons (rods and cones) that convert light energy to electrochemical neural impulses.
Rods—photoreceptors that detect black, white, and gray and that detect movement. Rods are necessary for peripheral and dim-light vision when cones do not respond. Distributed throughout the retina, except none are in the fovea.
Cones—photoreceptors that detect color and fine detail in daylight or in bright-light conditions. Most concentrated at the fovea of the retina, none are in the periphery.
Optic nerve—nerve formed by ganglion cell axons; carries the neural impulses from the eye to the thalamus of the brain.
Acuity—ability to detect fine details, sharpness of vision. Can be affected by small distortions in the shape of the eye.
Normal vision—rays of light form a clear image on the retina of the eye.
Nearsighted—too much curvature of the cornea and/or lens focuses image in front of the retina so nearby objects are seen more clearly than distant objects.
Farsighted—too little curvature of the cornea and/or lens focuses the image behind the retina, so distant objects are seen more clearly than nearby objects.
Dark adaptation—increased visual sensitivity that gradually develops when it gets dark.
Bipolar cells—second layer of neurons in the retina that transmit impulses from rods and cones to ganglion cells.
Ganglion cells—third layer of neurons in the retina, whose axons converge to form the optic nerve.
Blind spot—region of the retina where the optic nerve leaves the eye so there are no receptor cells; creates an area with no vision.
Feature detectors—individual neurons in the primary visual cortex/occipital lobes that respond to specific features of a visual stimulus.
Parallel processing—simultaneously analyzing different elements of sensory information, such as color, brightness, shape, etc.
Trichromatic theory—proposed mechanism for color vision with cones that are differentially sensitive to different wavelengths of light; each color you see results from a specific ratio of activation among the three types of receptors.
Opponent-process theory—proposed mechanism for color vision with opposing retinal processes for red–green, yellow–blue, white–black. Some retinal cells are stimulated by one of a pair and inhibited by the other.
Sensory adaptation—temporary decrease in sensitivity to a stimulus that occurs when stimulation is unchanging.
Attention—the set of processes from which you choose among the various stimuli bombarding your senses at any instant, allowing some to be further processed by your senses and brain.
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