Chapter 4 Sensation And Perception

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Sensation

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 info.

Perception

Process that makes sensory patterns meaningful. Perception 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.

Transduction

Transformation of one form of energy into another especially the transformation of stimulus information into nerve signals by the sense organs.

Sensory Adaptation

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.

Absolute Threshold

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.

Difference Threshold

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.

Weber's Law

This concept says that size of JND is proportional to the intensity of the stimulus; the JND is large when the stimulus intensity is high and is small when the stimulus intensity is low. ( This concept has no connection with Ann Weber, one of this books authors)

Fechner's Law

The magnitude of a stimulus can be estimated by the formula S =k log R, where S = sensation, R=stimulus, and k- a constant that differs for each sensory modality (sight, touch , temp, etc)

Steven's Power Law

Law of magnitude estimation that is more accurate than Fechner's law and covers a wider variety of stimuli. It is represented by the formula S=kI^a, where S= sensation, K= constant, I = stimulus intensity, and a= power exponent that depends on the sense being measured.

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.

Retina

Thin, light-sensitive layer at back of the eyeball. Retina contains millions of photoreceptors and other nerve cells

Photoreceptors

Light- sensitive cells (neurons) in retina which converts light energy to neural impulses. The photoreceptors are as far as light gets into the visual system.

Rods

Photoreceptors in the retina that are especially sensitive to dim light but not to colors. Strange as it may seem, they are rod shaped.

Cones

Photoreceptors in the retina that are especially sensitive to colors but not to dim light. You may have guessed that cones are cone-shaped.

Fovea

Tiny area of sharpest vision in the retina.

Optic Nerve

The bundle of neurons that carries visual info from the retina to the brain.

Blind Spot

The point where optic nerve exists the eye and where there are no photoreceptors. Any stimulus that falls on this area cannot be seen.

Brightness

A psychological sensation caused by the intensity of light waves.

Color

Aka "hue" color is not a property of things in the external worlds. Rather, it is psychological sensation created in the brain from info obtained by the eyes from the wavelengths of visible light.

Electromagnetic Spectrum

The entire range of electromagnetic energy, including radio waves, X rays, microwaves, and visible light

Trichromatic Theory

The term for Sternberg's theory of intelligence; so called because it combines three main forms of intelligence.

Opponent-process theory

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 colors sensation from the bipolar cells onward in the visual system. Theory of emotion which theorizes that emotions have pairs. When one is triggered, the other is suppressed.

Afterimages

Sensations that linger after the stimulus is removed. Most visual afterimages are negative afterimages, which appear reversed colors.

Color Blindness

Typically a genetic disorder that prevents an individual from discriminating certain color. Most common form is red-green color blindness.

Frequency

The number of cycles completed by a wave in a given amount of time, usually a second.

Amplitude

The physical strength of a wave. This is usually measured from peak (top) to valley (bottom) on a graph of the wave.

Tympanic Membrane

The eardrum.

Cochlea

The primary organ of hearing; a coiled tube in the inner ear, where sound waves are transuded into nerve messages.

Basilar Membrane

Thin strip of tissue sensitive 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 sounds waves are converted into nerve activity.

Pitch

Sensory characteristic of sound produced by the frequency of sound wave.

Loudness

Sensory characteristic of sound produced by the amplitude of the sound wave.

Timbre

Quality of a sound wave that derives from the wave's complexity. Timbre comes from the Greek word for "drum" as does the term tympanic membrane or eardrum.

Conduction deafness

Inability to hear resulting from damage to structures of the middle or inner ear.

Nerve Deafness

Inability to hear that is linked to a deficit in the body's ability to transmit impulses from the cochlea to the brain, usually involving the auditory nerve or higher auditory processing centers.

Vestibular Sense

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 the auditory nerve.

Kinesthetic Sense

The sense of body position and movement body parts are relative to each other.

Olfaction

The sense of smell.

Pheromones

Chemical signals released by organisms to communicated with other member of their species. Pheromones are often used by animals as sexual attractants. It is unclear whether or not humans employ pheromones.

Gustation

The sense of taste- from the same word roots as "gusto" also called the gustatory sense.

Skin Senses

Sensory systems for processing touch, warmth, cold, pain, texture.

Gate- control theory

An explanation for pain control that proposes we have neural "gate "that can under some circumstances block incoming pain signals.

Placebo Effect

Response to a placebo (fake drug) cause by subjects' belief that they are taking real drugs.

Percept

Meaningful product of perception often an image that has been associated with concepts, memories of events, emotions and motives.

Feature Detectors

Cells in the cortex that specialize in extracting certain features of a stimulus.

Binding Problem

Refers to the process used by the brain to combine the results of many sensory operation into a single percept. This occurs for example when sensations of a color, shape, boundary, and texture are combined to produce the percept of a persons face. No one knows exactly how the brain does this. Thus the biding problem is one of the major unsolved mysteries in psychology.

Bottom-up processing

Perceptual analysis that emphasizes characteristics of the stimulus, rather than our concepts and expectations." Bottom" refers to the stimulus Which occurs at the first step of perceptual processing.

Top-down Process

Perceptual analysis that emphasizes the perceiver's expectations, concept memories, and other cognitive factors, rather then being driven by the characteristics of the stimulus."Top" refers to mental set in the brain which stands at the "top" of the perceptual processing system.

Perceptual constancy

Ability to recognize the same object as remaining "constant" under different conditions , such as changes in illumination, distance , or location.

Illusion

You have experienced an illusion when you have a demonstrably incorrect perception of a stimulus pattern, especially one that also fools others who are observing the same stimulus. (if no one else sees it the way you do you could have having a delusion or hallucination.

Ambiguous Figures

Images that are capable of more than one interpretation. There is no "right "way to see an ambiguous figure.

Gestalt Psychology

A historical school of psychology that sought to understand how the brain works by studying perception and perceptual learning. Gestalt psychologists believed that percepts consist of meaning wholes.

Figure

Part of a pattern commands attention. The figure stands out against the ground.

Ground

Part of pattern that does not command attention the background.

Closure

The Gestalt principle that identifies the tendency to fill in gaps in figures and see incomplete figures as complete.

Laws of perceptual grouping

The Gestalt principles of similarity, proximity, continuity, and common fat. These "laws" suggest how our brains prefer to group stimulus elements together to form a percept.

Law of similarity

The Gestalt principal that we tend to group similar objects together in our perceptions.

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 that share the common motion or destination.

Law of Pragnanz

Most general Gestalt principle, which states that the simplest organization, requiring the least cognitive effort, will emerge as the figure. Pragnanz Shares a common root with pregnant and so carries the idea of a "fully developed figure". That is our perceptual system prefers to see a fully developed Gestalt such as a complete circle as opposed to a broken circle.

Binocular cues

Info taken in by both eyes that aids in depth perception, including binocular convergence and retinal disparity.

Monocular cues

Info about depth that relies on the input of just one eye-includes relative size, light and shadow, interposition, relative motion, and atmospherics perspective.

Perceptual set

Readiness to detect a particular stimulus in a given context as when a person who is afraid interprets an unfamiliar sound in the night as a threat.

Learning-based Inference

View that perception is primarily shaped by learning or experience rather than by innate factors.

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