Psychology: Sensation and Perception

Sensation

Sensation

Process by which the sensory receptors and nervous system receive and represent stimulus energies from our environment

Perception

Process by which the brain organizes and interprets sensory information, transforming it into 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

-Draws on one’s experiences and expectations

Basic steps to the Sensory Systems

Receive sensory stimulation

Transform the stimulation into neural impulses

Deliver the neural information to the brain

Absolute Threshold

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

Subliminal

Below an individual’s absolute threshold for conscious awareness

Difference Threshold

-Minimum difference between two stimuli required for detection 50 percent of the time

-Individuals experience the difference threshold as a just noticeable difference (or jnd).

Weber’s law

Principle that two stimuli must differ by a constant minimum percentage to be perceived as different

-Exact percentage differs based on the stimulus.

priming

Researchers use _______ to activate unconscious associations.

stimulus

Individuals can evaluate a ________, even when they are not consciously aware of it.

subliminal sensations

Individuals can be affected by ________ ________

subliminal sensations

Stimuli that are so weak that people do not consciously notice them

Sensory Adaptation

-Reduced sensitivity in response to constant stimulation

-Helps focus on informative changes in the environment without being distracted by background chatter

-Influences perceptions of emotions

Perceptual Set

Mental predisposition to perceive one thing, rather than another

-Affects what an individual sees, hears, tastes, and feels

Context, Motivation, and Emotion

• Affect interpretations of a situation

• Context creates expectations that influence individual perception.

• Motives provide energy to work toward a goal.

  • Can cause bias in interpreting neural stimuli

  • Experiences, assumptions, and expectations can shape and color views of reality via top-down processing.

Wavelengths

___________ visible to the human eye extend from the shorter waves of blue-violet light to the longer waves of red light.

Wavelength

Distance from the peak of one light wave to the peak of the next

Hue

Dimension of color that is determined by the wavelength of light

Intensity

Amount of energy in a light wave

• Influences what individuals perceive as brightness or loudness

• Determined by the wave’s amplitude or height

short wavelength (bluish colors)

high frequency (high-pitched sounds)

great amplitude

bright colors; loud sounds

long wavelength (reddish colors)

low frequency (low-pitched sounds)

small amplitude

dull colors; quiet sounds

iris

controls the amount of light entering the eye

lens; pupil

light hits the ____ in the eye after passing through the _____

Fovea

point of central focus

retina

light-sensitive inner surface of the eye

contains:

receptor rods and cones

layers of neurons that begin the processing of visual information

rods

detect black, white, and grey

necessary for peripheral and twilight visions, when cones do not respond

cones

detect fine detail and give rise to color sensations in daylight and well-lit conditions

optic nerve

carries neural impulses from the eye to the brain

blind spot

point where the optic nerve leaves the eye and has no receptor cells

6 million

how many cones are there

120 million

how many rods are there

center

where are the cones located in the retina

periphery

where are the rods located in the retina

low

what is light sensitivity like in dim light for the cones

high

what is light sensitivity in dim light for the rods

high

what is color sensitivity like for the cones

low

what is color sensitivity like for the rods

high

what is detail sensitivity like for the cones

low

what is detail sensitivity like for the rods

Young-Helmholtz trichromatic theory

-The retina contains three different types of color receptors—red, green, and blue.

-When stimulated in combination, these receptors can produce the perception of any color.

opponent-process theory

-Opposing retinal processes enable color vision.

-Opposing retinal processes include red-green, yellow-blue, and white-black.

color processing

-combines the trichromatic theory and the opponent-processing theory and occurs in two stages.

-The retina’s red, green, and blue cones respond in varying degrees to different color stimuli.

-The cones’ responses are processed by opponent-process cells.

Feature Detectors

-Nerve cells in the brain that respond to specific features of a stimulus

-Include shape, angles, or movement

-Pass scene-specific information to other cortical areas, where more complex patterns are interpreted

-One temporal lobe area by the right ear enables a person to perceive faces.

-A specialized neural network helps recognize faces from many viewpoints.

0Interaction between feature detectors and supercells provides instant analyses of objects in the world around people.

Parallel Processing

-Processing many aspects of a problem or scene at the same time

-Brain’s natural mode of information processing for many functions, including vision

-Damage to neural workstations due to a stroke may render a person unable to perceive movement.

visual information processing

scene→retinal processing→feature detection→parallel processing→recognition

Gestalt

-Refers to an organized whole

-these psychologists emphasized the human tendency to integrate pieces of information into meaningful wholes.

perceptual organization

-The human brain registers information about the world, filters incoming information, and constructs perceptions.

-Principles in perceptual organization:

-Form perception

-Depth perception

-Perceptual constancy

figure-ground

Organization of the visual field into objects that stand out from their surroundings

grouping

The perceptual tendency to organize stimuli into meaningful groups

-Proximity

-Continuity

-Closure

depth perception

-Ability to see objects in three dimensions, although images that strike the retina are two-dimensional

-Allows people to judge distance

-Partly innate in other animals

Visual Cliff

-Devised by Eleanor Gibson and Richard Walk

-Laboratory device for testing depth perception in infants and young animals

-Most infants refuse to crawl across the visual cliff.

-Crawling, no matter when it begins, seems to increase an infant's fear of heights.

-Miniature cliff with a glass-covered drop-off

-Helps determine whether crawling infants and newborn animals can perceive depth

-Even when coaxed, infants refuse to climb onto the glass over the cliff.

Binocular Cue

Depends on the use of two eyes

retinal disparity

The calculation of distance by the brain by comparing images from both eyes

-Used by 3-D film makers

monocular cue

Cue available to each eye separately

-Includes relative height, relative size, interposition, relative motion, linear perspective, and light and shadow

motion perception

-The human brain computes motion based partly on its assumption that:

-Shrinking objects are moving away

-Enlarging objects are approaching

-Humans are imperfect at motion perception.

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

perceptual constancy

Perceiving objects as unchanging, even as illumination and retinal images change

-Objects have consistent color, brightness, shape, and size.

color constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

shape constancy

perception that the form of a familiar object is constant, even when retinas receive changing images of them

size constancy

perception that objects have a constant size, even when one’s distance from them varies

the moon illusion

-the moon looks up to 50 percent larger when near the horizon than when high in the sky

-monocular cues to an object’s distance make the horizon Moon appear farther away

-if it’s farther away, the brain assumes that it must be larger than the Moon high in the night sky

-when the distance cues are taken away, the object will immediately shrink

perceptual interpretation

-according to Immanuel Kant, human beings have the innate ability to process sensory information

-John Locke argues that individuals also learn to perceive the world through their experiences

-learn to link an object’s distance with it’s size

experience and visual perception

-research findings

-the effect of sensory restriction on infant cats, monkeys, and humans suggests that there is a critical period for normal sensory and perceptual development

-in humans and other animals, sensory restrictions do not cause permanent harm later in life

perceptual adaptation

-ability to adjust to changed sensory input

-includes adjustments to an artificially displaced or even inverted visual field

-humans constantly adjust to changed sensory input

-early nurture sculpts what nature has provided

-experience guides, sustains, and maintains the pathways in the brain that enable perceptions

audition

sense or act of hearing

-helps individuals adapt and survive

-provides information and enables relationships

-enables individuals to communicate invisibly

-hearing loss is an invisible disability

-humans are acutely sensitive to faint sounds and sound differences

sound waves

-vary in shape

-moving molecules of air create waves of compressed and expanded air

-ears detect these brief air pressure changes

characteristics:

-amplitude or height

-determines the perceived loudness of sound waves

-frequency or length

-number of complete wavelengths that pass a point in a given time

-pitch

pitch

a tone’s experienced highness or lowness that depends on frequency

decibels

sound is measured in __________.

process of sound waves

strike eardrum and vibrate→tiny bones in middle ear pick up vibration and transmit them to the cochlea (inner ear)→ripples in cochlea fluid bend hair cells on the surface and trigger impulses in nerve cells→axons from nerve cells transmit signal to auditory cortex

sensorineural hearing loss

-caused by damage to the cochlea’s receptor cells or to the auditory nerves

-called nerve deafness

conduction hearing loss

-caused by damage to the mechanical system that conducts sound waves to the cochlea

-less common form of hearing loss

skin senses

pressure, warmth, cold, and pain

pain

-reflects both bottom-up sensations and top-down sensations

-biopsychosocial event

are not

pain signals ______ processed by specialized receptors

nociceptors

sensory receptors that detect hurtful temperatures, pressure, or chemicals

experience of pain

depends on inherited genes and physical characteristics

misinterprets

brain can sometimes _______ its signals and create pain

more

humans feel ____ pain when others seem to be experiencing pain

pain control therapies

drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation training, and thought distraction

endorphins

natural painkiller released by the brain

have a soothing effect that enables pain reduction

placebos

help dampen the central nervous system’s attention and responses to painful experiences

placebo and distraction

maximum pain relief can be obtained by

endorphins and distraction

activate brain pathways that decrease pain and increase tolerance

hypnosis

-social interaction where one person suggest to another that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur

-inhibits pain-related brain activity

-explained by the social influence theory and the dissociation theory

-does not block the sensory input itself, but it may block individual’s attention to those stimuli

dissociation

divided consciousness

sweet

energy source

salty

sodium essential to physiological processes

sour

potentially toxic acid

bitter

potential poisons

umami

proteins to grow and repair tissue

taste

(sweet, sour, salty, bitter, and umami)

-gives pleasure and helps people survive

-can be influenced by learning and expectations

-number of taste buds and taste sensitivity decrease with age

-smoking and alcohol can speed up the loss of taste buds

200 or more taste buds

each bump on the top and sides of the tongue contains ___ __ ____ _____ ____

50-100 taste receptor cells

each taste bud contains a pore with -_ _____ ________ _____

food molecules

each receptor reacts to different types of ____ _________ and sends messages to the brain

smell

-enabled by millions of olfactory receptors that respond selectively to odors

-bypass the thalamus and directly alert the brain

-odor molecules exist in many shapes and sizes

-smell’s appeal, or the lack of it, depends partly on learned associations

-odors can evoke strong feelings, memories, and behaviors

20 million

humans have some __ _______ olfactory receptors

frontal; temporal

information from the taste buds travels to an area between the ______ and ________ lobes of the brain

Kinesthesia

system for sensing the position and movement of individual body parts