Sensation and Perception Chapter 6

Sensation

Process by which sensory receptors and nervous system receive and represent

stimulus energies from environment

Sensory receptors

Sensory nerve endings that respond to stimui

Perception

Process of organizing and interpreting sensory information, enabling recognition of meaningful objects and events

Bottom-up processing

Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information

Top-down processing

Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations

Steps Basic to All Sensory Systems

Receive: sensory stimulation, often using specialized receptor cells

Transform: that stimulation into neural impulses

Deliver: the neural information to our brain

Transduction

Involves conversion of one form of energy into another. In sensation, the transformation of stimulus energies, such as sights, sounds, and smells, into neural impulses that the brain can interpret

Psychophysics

Study of relationships between detectable physical energy and its effects on psychological experiences

Absolute threshold

Minimum stimulus energy needed to detect a particular stimulus 50 percent of the time

Subliminal

Input below the absolute threshold for conscious awareness

Signal detection theory

Predicts how and when faint stimulus will be

detected amid background noise

Difference threshold (just noticeable difference)

Minimum difference a person can detect between any two stimuli half the time; increases with stimulus size

Weber’s law

Principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

Subliminal sensations

Involves stimuli so weak that these are not consciously noticed

Priming

Used to activate unconscious association

Subliminal persuasion

May produce a fleeting, subtle, but not powerful, enduring effect on behavior. Experiments discount attempts at subliminal advertising and self-improvement.

Sensory adaptation

Is diminished sensitivity a consequence of constant stimulation. Increases focus by reducing background chatter. Influences how the world is perceived in a personally valuable way. Influences emotions

Perceptual set

Mental predisposition to perceive one thing and not another; what one feels, sees, tastes, and hears; stereotype

Schemas

Organize and interpret unfamiliar information through experience. Preexisting _______ influence top-down processing of ambiguous

sensation interpretation, including gender stereotypes.

Context effects

Given stimulus may trigger different perceptions because of the immediate context.

Motives

Provide energy when working toward a goal. Can bias interpretations of neutral stimuli.

Emotions

can move our perceptions in one direction or another

Wavelength

Distance from peak of one light or sound wave to peak of next. Electromagnetic wavelengths vary from short blips of cosmic rays to long pulses of radio transmissions

Hue

Dimension of color that is determined by the wavelength of light; what we know as color names blue, green, and so forth

Intensity

Amount of energy in a light wave or sound wave, which influences what those with typical vision or hearing perceive as brightness or loudness. Is determined by the wave’s amplitude (height)

Retina

Light-sensitive back inner surface of eye, which contains receptor rods and cones, plus layers of neurons that begin processing of visual information

Accommodation

Process by which eye’s lens changes shape to focus near or far objects on retina

Frequency

Includes the number of complete wavelengths that can pass a point in a given time, depends on wavelength

amplitude

height from peak to trough (top to bottom). Wave ____ determines brightness of colors (and loudness of sounds).

Rods

Retinal receptors that detect black, white, and gray and that are sensitive to movement; necessary for peripheral and twilight vision when cones don’t respond. Sensitive to faint light

Cones

Retinal receptors that are concentrated near center of retina; function in daylight or in well-lit conditions. Detect fine detail and give rise to color sensations. Sensitive to detail and color

Optic nerve

Nerve that carries neural impulses from eye to brain

Blind spot

Point at which optic nerve leaves eye, creating “blind” spot because no receptor cells are located there

Fovea

Central focal point in retina around which eye’s cones cluster

Ganglion axons

form optic nerve run to thalamus, where they synapse with neurons that run to visual cortex

Retina’s neural layers

pass along electrical impulses and help to encode

and analyze sensory information.

optic chiasm

Half of each eye’s sensory information

arrives in opposite side of brain, by

crossing the X-shaped ____.

Color Processing

Occurs in two stages:

1. Young-Helmholtz Trichromatic Theory – Red, green, and blue cones in the retina respond to different color stimuli.

2. Opponent-Process Theory – Cone signals are further processed by opponent-process cells (red-green, blue-yellow, black-white).

Feature detectors

Are nerve cells in occipital lobe’s visual cortex that respond to scene’s specific visual features — to particular edges, lines, angles, and movements

Supercell clusters

teams of cells respond to one stimulus type, integrate information, and fire only when cues collectively indicate direction of someone’s attention and approach

Fusiform face area

Specialize neural network in the temporal lobe that enables perception and recognition of faces from varied viewpoints. Occurs separately from its object perception.

Parallel processing

Processing multiple aspects of stimulus or problem (motion, form, depth, color) simultaneously

Face Recognition

To recognize a face, our brain integrates information projected by our retinas to several visual cortex areas and compares it with stored information, thus enabling our fusiform face area to recognize the face

grandmother cells

supercells that respond best to one specific object.

Gestalt principles

Form perception

Depth perception

Perceptual constancy

gestalt

an organized whole. Tendency to integrate pieces of information into meaningful wholes.

Figure-ground

Organizing visual field into objects that stand out from their surroundings. Perceiving any object (the figure) as distinct from its surroundings (the ground).

grouping

the perceptual tendency to organize stimuli into coherent groups.

grouping strategies

Proximity, continuity, closure

Depth perception

Ability to see objects in three dimensions, although images that strike retina are two-dimensional. Allows us to judge distance. Is present, at least in part, at birth in humans and other anima

visual cliff

a laboratory device for testing depth perception in infants and young animals.

Binocular cues

Depth cue, such as retinal disparity, that depends on use of two eyes

Retinal disparity

Binocular cue for perceiving depth. Brain calculates distance by comparing retinal images from two eyes. Greater the disparity (difference) between two images, the closer the object.

Monocular cue

Depth cue, such as interposition or linear perspective, available to either eye alone

motion perception

When large and small objects move at same speed, large objects appear to move more slowly

Stroboscopic movement

Occurs when brain perceives rapid series of slightly varying images as continuous movement

Phi phenomenon

Is illusion of movement created when two or more adjacent lights blink on and off in quick succession

Perceptual constancy

Perceiving objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change. Color and brightness constancies. Shape and size constancies.

Color Constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters wavelengths reflected by object. Involves brain’s computations of the light reflected by the object relative to objects surrounding it

Brightness constancy (light constancy)

Perceiving object as having constant brightness, even as its illumination varies. Depends on relative luminance

Size constancy

Perception of objects as having constant size even when distance from them varies. Perception of form of familiar objects as constant even when retina receives changing image

Restored vision and sensory restriction

there is a critical period for typical sensory and perceptual development. Without stimulation, typical connections do not develop.

Perceptual adaptation

Ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field

Hearing

Aids in adaptation and survival. Provides information and enables relationships. Facilitates communication invisibly. Humanizes

Hearing loss

invisible disability. increases risk of depression and anxiety

Sound waves

From the environment into the brain. ____ compress and expand air molecules. Ears detect these brief pressure changes.

Sound intensity

Is measured in decibels. Zero decibels represent the absolute threshold for hearing. Every 10 decibels corresponds to a tenfold increase in _____. Prolonged exposure to sounds above 85 decibels can produce hearing loss.

Sensorineural hearing loss

(or nerve deafness)

Damage to cochlea’s hair cell receptors or auditory nerve

Conduction hearing loss

Damage to mechanical system (eardrum and middle ear bones) that conducts sound waves to the cochlea

toxic noise

• Prolonged loud noise (e.g., ear-splitting music) can cause hearing loss.

• Any noise too loud to talk over may be harmful, especially with repeated exposure.

• Ringing ears signal potential hearing damage, like the decibel equivalent of bleeding.

teen hearing loss

has risen by a third since early 1990s, now affecting 1 in 6 teens.

Nerve deafness

cannot be reversed

Cochlear implant

A device that converts sound into electrical signals and stimulates the auditory nerve via electrodes in the cochlea. Most effective for young children, especially if received before age 1, during the critical period for language development.

loudness

is related to intensity of hair cell response; numbness. If hair cell loses sensitivity to soft sounds, it may still respond to loud sounds.

Place theory in hearing (place coding)

In hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated

Frequency theory (temporal coding)

In hearing, the theory that the rate of nerve impulses traveling up auditory nerve matches frequency of a tone, and enables us to sense its pitch; explains low pitches

volley principle

Modification of frequency theory stating that a cluster of nerve cells can fire neural impulses in rapid succession. Combination of place and frequency theories. Handle pitches in intermediate range

Locating Sound

Sound waves strike one ear sooner and more intensely than they strike other ear. From this information, brain can compute sound’s location.

Touch

mix of four basic, distinct skin senses: Pressure,

warmth, cold, and pain

pain

Influenced by biological, psychological, and social-cultural factors. Involves both bottom-up sensations and top-down cognition. Varies across individuals and groups and is best understood through a biopsychosocial approach.

Biological influences

• Nociceptors detect harmful temperatures, pressure, or chemicals.

• Neural networks in the brain process these sensations and create pain perceptions.

• Pain experiences vary among individuals due to factors like genes, physical characteristics, and gender differences.

• Fearing and feeling pain can influence pain perception.

Nociceptors

sensory receptors that detect hurtful temperatures, pressure, or chemicals

Gate-control theory

Spinal cord contains neurological gate that controls transmission of pain messages to brain

Psychological influence

Pain is influenced by focus placed on it. Memories of pain record peak moments and end of pain

Social-cultural influences

Pain is the product of attention, expectations, and culture. Variation with social situation and cultural traditions. Pain enhancement occurs when others seem to also experience it. Empathy for another’s pain may partly mirror actual pain.

Placebo

Reduces CNS attention and responses to pain

Distraction

Draws attention away from painful stimulation. Virtual reality play reduces brain’s pain-related activity.

Social influence theory

Dual-processing state sensory information does not reach areas where pain-related information is processed

Dissociation theory

Hypnosis is special dual-processing state of dissociation; split between different levels of consciousness.

• Selective attention

• Posthypnotic suggestion

Taste

• Involves basic sensations: Sweet, sour, salty, bitter, umami.

• A chemical sense where receptors send messages to matching brain cells in the temporal lobe; includes supertasters.

• Influenced by learning, expectations, and perceptual bias.

• Has a survival function.

Sweet

Energy source

Salty

Sodium essential to physiological processes

Sour

Potentially toxic acid

Bitter

Potential poisons

Umami

Proteins to grow and repair tissue

smell

• Chemical sense involving hundreds of receptors.

• Odors trigger combinations of receptors, creating patterns interpreted by the olfactory cortex.

• Can evoke strong memories and is influenced by cultural experiences.

Information from taste buds

travels to area between frontal and temporal lobes of brain.

Kinesthesia

System for sensing position and movement of individual body parts. Interacts with vision

Vestibular sense

Sense of body movement and position, including sense of balance

Sensory interaction

Principle that one sense can influence another, as when smell of food influences its taste. Senses are not totally separate information channels.