chem chap 5 sensation and preparation

light

• electromagnetic energy classified by 3 properties

• wavelength: distance from one energy cycle to the next (shorter wavelength goes deeper in water)

• intensity (amplitude): amount of light falling on an object; change in intensity = change in brightness

• purity: mix of wavelength present; influences saturation of perceived colors

transduction

conversion of one form of energy to another

cornea + lens

cornea: protective outer layer of eyes

lens: clear flexible piece of tissue that’s behind the pupil 

both are focusing process of the eye

pupil + iris

pupil: a hole in ring of tissue called iris

iris: gives the eye its distinctive color 

• tightening around iris = change in pupil size = change amount of light entering eye 

light pass through these

accommodation

• focusing of human eye by changing shape of lens

• influenced by distance between lens and object being viewed

• object far away = lens is long and thin

• object close = lens is thick and round

retina

• thin layer of tissue in back of eye

• light gets translated into inner layer of the brain 

• has light sensitive receptor cells that convert energy into neural impulses

2 types of receptor cells in retina (photoreceptos)

• rods

• cones

• both adapt at different rates

rods

• 120 million in eye

• long and thin

• more sensitive to light

• can generate visual signals

• not sensitive to visual detail/color

• on sides of retina

cones

• 6 million in eye

• short, thick, tapered

• in center of retina

• in a central pit called fovea 

• needs high levels of light to operate 

• processes fine detail, visual acuity and early processing of color (high sensitivity to visual detail) 

bipolar cells

receive impulse from rod/cone; goes from receptors to bipolar to ganglion cells; interprets visual message

receptive field

each ganglion cell has receptive field, receives input from receptor cells and only responds when light shines on retina

• cells that have center surrounded receptive fields means light falls in center of field then number of signals sent to brain increases. light shown on side, cell will stop / decrease signals

optic nerve

collection of nerve fibers that carry impulse from retina to brain

blind spot

from no receptor cells where optic nerve leaves retina

dark adaptation

caused by depletion-regeneration process in rods and cones when going from light to dark 

optic chiasm

• where info from optic nerve travels to separate hemispheres of brain

• left visual field goes to right half of each retina goes to right hemisphere and vice versa 

lateral geniculate nucleus (LGN)

major relay station in the thalamus where visual signals go to

superior colliculus

only 10% of signals go here, located in midbrain

feature detectors

• cells that respond to visual events, ex. pattern of light and dark

• simple cell: responds only when small bar of light is shown into eye at particular angle

prosopagnosia

ability to recognize faces is lost

trichromatic theory

• brain determines color by comparing activity level of 3 primary receptors—primary color means one receptor strongly activated

• dichromats: 2 cones instead of 3 (color blindness) 

• short wavelength (420, blue)

• medium wavelength (530, green)

• long wavelength (670, red)

opponent process theory

receptors in visual field that respond positively to one color type and negatively to another; why we see 6 primary colors 

bottom-up processing

visual system performs analysis of actual sensory message, pattern on retina

top-down processing

using knowledge, beliefs, and expectations about the world to interpret and organize what we see

gestalt principles of organization 

1. proximity: small stuff together = group together as some object 

2. similarity: items that share physical properties are placed into same set

3. closure: if figure has a gap, still seen as whole

4. good continuation: if lines cross or are interrupted, still seen as continuously flowing line

5. common fate: if things appear to be moving in same direction, people group them together 

recognition by components

only 2 or 3 geons needed to recognize an object; geons: geometric icons, simple geometric forms

monocular depth cues

require input from only one eye

binocular depth cues

• cues produced by 2 eyes ex. putting finger in front of eye and position changing depending on which eye you open 

• retinal disparity: difference between location of 2 images in 2 eyes; amount of disparity changes with distance from a point of fixation

• convergence: the closer the stimulus, the more the eyes turn inward on another

phi phenomenon

illusion of motion

perceptual constancy

perceives object to remain the same even when undergone physical change (size constancy, shape constancy) 

affordances

nature designed perceptual systems to help determine what behaviors we can perform 

sound

physical message delivered to auditory systems; mechanical energy which requires a medium to move

frequency

number of times wave moves from peak to peak per second 

pitch

when frequency of sound varies

pressure amplitude

measure of sound; changes in intensity = changes in loudness

pinna

external flap of tissue, helps capture sound

tymbanic membrane

eardrum, responds to incoming sound wave by vibrating, pattern goes to 3 bones in middleear

middle ear

malleus, incus, and stapes. help intensify vibration pattern and prepare for passage into inner ear 

cochlea

bony small shaped sound processor inside inner ear, sound energy translated into neural impulses 

oval window

where stapes is connected to opening in cochlea

basliar membrane

stapes vibrates, causes fluid inside cochlea to move to flexible membrane

hair cells

in cochlea and bend by movement of basliar membrane

auditory nerve

neural impulses from hair cells leave cochlea to auditory cortex; message received in right ear goes to pathways to left hemisphere

place theory

pitch determined by specific place on basliar membrane where hair cells respond

frequency theory

pitch determined by frequency of impulses going up auditory pathway; increase rate of firing = increase in pitch perceived

thermoreceptors

• cold fibers: respond to cooling of skin by increase in production of impulses

• warm fibers: respond when temp of skin increases

pain

adaptive reaction that body generates in response to events that cause tissue damage

gate control theory

spinal cord prevents pain receptors from heading to brain

kinesthesia

ability to sense position and movement of one’s body parts

semicircular canals

3 small fluid filled canals within each ear

vesticular sacs

receptor cells located in inner ear organs, quickly transmit appropriate orientation info to the brain ; sense change in acceleration 

olfaction

sense of smell

olfactory bulb

receptor fibres take message here, located at bottom region of brain then sent to several areas of brain 

gustation

sense of taste; sweet, salty, bitter, sour; sensation produced by taste receptors

flavor

influenced by taste, smell and visual appearance and expectation of the food; gustation experience

psychophysics

ways to describe transition from physical to psychological in form of mathematical laws

absolute threshold

level of intensity that lifts the stimulus over threshold of conscious awareness

signal detection

• compares hits, where stimulus is correctly detected, to false alarms, where observer claims stimulus is present but is not

• Stimulus present and says “yes” : hit

• stimulus present and says “no” : miss

• stimulus not present and says “yes” : false alarm

• stimulus not present and says “no” : correct rejection

difference threshold

smallest detectable difference in magnitiude ofa stimuli

JND

just noticeable difference

weber’s law

louder the standard stimulus, the more volume needed before difference in loudness is detected

sensory adaptation

body quickly adapts to a sensory that remains constant