PSY 2301: Chapter 6 Sensation and Perception

sensation

when sensory information is detected by a sensory receptor

transduction

conversion of sensory stimulus energy to action potential

absolute threshold

sensitivity of a given sensory system to the relevant stimuli can be expressed as this

minimum amount of stimulus energy that must be present for the stimulus to be detected 50% of the time; stimulus reaches a physiological threshold when it is strong enough to excite sensory receptors and send nerve impulses to the brain

below threshold (subliminal) - receive is but are not aware of it

just noticeable different of difference threshold

interested in how much different in stimuli is required to detect a difference between them

depends on threshold intensity

ernest weber - weber law - difference threshold is a constant fraction of the original stimulus

perception

refers to the way sensory information is organized, interpreted, and consciously experienced

involves bottom-up and top-down processing

top-down processing

previous experiences and expectations are first used to recognize stimuli

goal directed, slow, deliberate, effortful, and under your control

bottom-up processing

we sense basic features of stimuli and then integrate them

sensory adaptation

we often don’t perceive stimuli that remain relatively constant over prolonged periods of time

inattentional blindness

failure to notice something that is completely visible because the person is actively attending to something else and did not pay attention to other things

signal detection theory

ability to identify a stimulus when it is embedded in a distracting background

our perceptions can be affected by our

beliefs, values, prejudices, expectations, and life experiences

amplitude

distance from the center line to the top point of the crest or the bottom point of the trough

wavelength

length of a wave from one peak to the next

frequency

number of waves that pass a given point in a given time period (Hz)

visible spectrum

portion of the larger electromagnetic spectrum that we can see

380-740nm

EM includes

gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves

pitch

frequency of a sound wave is associated with our perception of the pitch

high frequency - high pitch

low frequency - low pitch

higher amplitude soudns means…

more loud sound (decibels)

timbre

refers to sounds period and is affected by interplay of frequency, amplitude, and timing od sound waves

cornea

transparent covering over the eye serves as barrier between inner eye and the outside world, involved in focusing light waves that enter the eye

pupil

small opening in the eye through which light passes, size of pupil can change as a function of light levels as well as emotional arousal

light levels are low - pupil dilated to let more light in

light levels are high - pupil constricts to reduce light in

iris

muscles that control pupil size and is colors part of eye

lens

a curved, transparent structure that serves to produce additional focus

attached to muscles that can change its shape to aid in focusing light that is reflected from near or far objects

fovea

in normal-sighted individuals, lens will focus images perfectly on a small indentation in the back of the eye (fovea) which part of the retina

contains densely packed specialized photoreceptor cells known as photoreceptor cells

retina

light sensitive lining of the eye

cones

specialized that work in bright light conditions

sensitive to acute detail and provide tremendous spatial resolution

can percieve color

rods

work in low light conditions

lack spatial resolution and color fucntion of cones, invovled in dimly lit environments and our percepetion of movement on periphery

night blindness

if your rods do not transform light into nerve impulses as easily and efficiently as they should, you will have difficulty seeing in dim light

optic nerve

axons from the retinal ganglion cells converge and exit through the back of the eye to form the optic nerve

carries visual information from the retina to the brain

blind spot

even when light from a small object is focused on the blind spot, we do not see it

not aware because 1) each eye gets a slightly different view of the visual field - blind spots don’t overlap; 2) visual system fills in the blind spot so that although we can’t respond to visual information that occurs in that portion of the visual field, we are not aware that information is missing

optic chiasm

optic nerve from each eye merges just below the brain in a point called the optic chiasm - x shaped structure that sits just below cerebral cortex at the front of the brain - visual information from right eye is given to left brain and vice versa

normal sighted individuals

• 3 different cones that mediate color vision - each maximally sensitive to a slightly different wavelength of light

trichromatic theory of color vision

all colors in the spectrum can be produced by combining red, green, and blue

opponent-process theory

color is coded in opponent pairs: black-white, yellow-blue, green-red

some visual system cells are excited by one of the opponent colors and inhibited by the other - cell excited by wavelengths associated with green would be inhibited by wavelengths associated with red

implication - we don’t get greenishreds or yellowishblue; afterimages

afterimage

describes the continuation of a visual sensation after the removal of the stimulus leading to negative afterimage

two visual theories work hand in hand

visual processing on retina - trichromatic theory

signal moves to brain - opponent process theory

depth perception

ability to perceive spatial relationships in 3-d space

binocular cues - 3D

rely on use of both eyes

• binocular disparity - slightly different view of the world that each of our eyes receive

monocular cues - 2D

cues that require only one eye

• linear perspective - we perceive depth when we see 2 parallel lines that seem to converge in an image

• interposition - partial overlap of objects

• relative size and closeness of images to the horizon

parts of the ear

• outer ear - pinna (visible part of ear); auditory canal; tympanic membrane

• middle ear - malleus (hammer); incus (anvil); stapes (stirrup)

• inner ear - semicircular canals involved in balance and movement (vestibular sense); cochlea (fluid filled snail shaped structure that contains hair cells)

sound traveling

sound waves travel along auditory canal and strike tympanic membrane causing is to vibrate - three ossicles move - stapes presses into membrane of cochlea (oval window) - fluid in cochlea moves and stimulates hair cells (auditory receptor cells of the inner ear embedded in the basilar membrane - thin strop of tissue within the cochlea) - hair cells generate neural impulses that travel along auditory nerve to brain - inferior colliculus - medical geniculate - nucleus of thalamus - auditory cortex in temporal lobe for processing

temporal theory of pitch perception

frequency is coded by the activity level of a sensory neuron - hair cell would fire action potentials related to frequency of the sound wave - frequency of action potentials of hair cells can’t account for the entire range - point where cells can’t fire any faster (Na+ channels)

place theory of pitch perception

different portions of basilar membrane are sensitive to sounds of different frequencies - base (high frequencies and pitch) and tip (low frequencies and pitch)

sound localization

monaural - one eared

binaural - two ears - horizontal axis relying on differences in vibration patterns of both ears

• interaural level differences - sound coming from right is more intense in right ear

• interaural timing difference - small difference in the time at which a given sound wave arrives at each ear

deafness

partial or complete inability to hear

• congenital deafness - born with it

• conductive hearing loss - problems delivering sound energy to the cochlea - blockage of ear canal

• sensorineural hearing loss -failure to transmit neural signals from cochlea to the brain - aging, head or acoustic trauma, infection, diseases, medications, environmental effects, tumors, toxins

  • meiniere’s disease - can cause sensorineural hearing loss - degeneration of inner ear structures that can lead to hearing loss, tinnitus, vertigo, increase in inner ear pressure

cochlear implant

electronic devices that consist of a microphone, speech processor, and electrode array - receives incoming sound information and directly stimulates the auditory nerve to transmit information to the brain

6 basic groupings of taste

sweet, salty, sour, bitter, unami, fatty content

taste buds

molecules from food and beverages we consume dissolve in saliva and interact with taste receptors on our tongue and in our mouth and throat

formed by groupings of taste receptor cells with hair like extensions that protrude into the central pre of the taste bud - life cycle of 10 days - 2 weeks - no long term effect of burning tongue

olfactory receptors

cells in mucuous membrane at top of nose - small hair like extensions are the sites for odor molecules dissolved in the mucus to interact with chemical receptros located on these extensions - chemical changes within cell result in signal sent to olfactory bulb - informaiton is sent to regions of limbic system and primary olfactory cortex

pheromones

many species respond to chemical messages sent by another individual - reproductive status of a potential mate

mesinner’s corpuscles

respond to pressure and lower frequency vibrations

pascinian corpuscles

detect transient pressure and higher frequency vibrations

merkel’s disks

respond to light pressure

ruffini corpuscles

detect strength

thermoception

temperature perception

nocireception

signal indicating potential harm and maybe pain

inflammatory pain

pain that signals some type of tissue damage

neuropathic pain - pain signals sent to the brain get exaggerated

congenital insensitivity to pain - congenital analgesia

detect differences in temperature and pressure but can’t experience pain - suffer injuries

vestibular sense

ability to maintain balance and body posture - utricle, saccule, and three semicircular canals are next to cochlea - are fluid filled and have hair cells which respond to movement of head and gravitational forces

proprioception

perception of body position

kinesthsia

perception of the body’s movement through space

gestalt psychology

brain creates a perception that is more than simply sum of available sensory inputs and does so in predictable ways in which we organize sensory information

figure ground relationship

segment visual world into figure and ground

figure - object or person that is the focus of the visual field

ground - background

proximity

things that are close to one another tend to be grouped together

similatiry

groups things that are alike to one another

continuity

law of continuity suggests that are more likely to perceive continues smooth flowing lines rather than jagged broken lines

principle of closure

states that we organize our perceptions into complete objects rather than as a series of parts

pattern perception

our ability to discriminate among different figures and shapes

perpetual hypotheses

educated guesses that we make while interpreting sensory information - informed by a number of factors, personalities, experiencies, and expectations