Unit 9 - Sensation and Perception

It's the day before :D

sensation

detecting physical energy in environment

• sound waves

• light waves

• molecules

perception

interpreting sensation.

providing:

• definition

• category

• understanding

reception

the absorption of physical energy by the receptors. Receptors can either be specialized cells that change with physical energy or the dendrites of a sensory neuron itself.

transduction

transition of physical energy → electrochemical pattern in the neuron (action potential)

thresholds

how much stimulation s required before an action potential is generated in reference to sensation

how much stimulation is required before sensory receptors respond.

absolute threshold

minimum amount if stimulation required to detect a stimulus 50% of the time it is presented.

difference threshold

minimum amount of additional stimulation required to notice a difference (either increase or decrease) in a stimulus 50% of the time.

sensory adaption

change in sensitivity when a sensory system is either stimulated or not stimulates for a period of time. can happen at the receptor level or higher in sensory processing

stimulation long period → decrease sensitivity

stimulation short period → increase sensitivity

*weak to moderate stimuli

signal-detection theory

a line of research in probability which examines the rewards or results we can get from detecting a sound or signal.

the researcher presents a very faint signal, and asks the subject whether or not the signal was present.

2 possible variables of concern in signal-detection theory

1. is a signal present?

2. does the subject indicate the signal is present?

*4 possible outcomes

4 possible outcomes of signal-detection theory

*the cost of a “hit” or “miss'“ can determine whether or not the subject reports the presence of a signal.

visible light

the portion of the electromagnetic spectrum that is visible to the human eye (detected by human’s photoreceptors).

range: 400 - 750 nanometers (nm)

400 nm = violet/blue

500 nm = green

700 nm = red

riris

colored area which overlies the muscles surrounding the pupil; controls amount of light entering the eye

pupil

opening in the eye that light passes through

lens

focuses light waves on the back of the eye. The lens is a transparent structure that adjusts its shape (accommodation) to help focus light onto the retina, enabling clear vision at various distances.

near-sightedness: image is focuses in front of the fovea

far-sightedness: image is focused behind the fovea

retina

light-sensitive lining of the back of the eye; contains photoreceptors; part of the brain

fovea

area of central focus; many photoreceptors, few ganglion cells

photoreceptors

light-sensitive; contain chemical that reacts with light waves.

two types:

• rods

• cones

rods

• 120 million

• outside fovea

• highly sensitive to light

• black/white/grey vision

• fuzzy vision

cones

• 6 million

• at fovea

• lower sensitivity to light

• color vision

• acute vision

dark and light adaption

light environment → cones

dark environment→ rods

blind spot

are of eye where ganglion axons leave the eye; no photoreceptors; thus “blind” in that area.

we tend to “fill in” missing details to smooth out out vision.

trichromatic theory

(Young/Helmholtz)

three different types of cones, each sensitive to different wavelengths of light

• short wavelength → violet/blue

• medium wavelength → green

• long wavelength → orange/red

opponent-process theory

(Hering)

we perceive color in paired opposites. bipolar cells have both excitatory and inhibitory synapses with the three types of cones; paired so that when one color is perceived, the other color is not.

paired:

red - green

blue - yellow

black - white

negative afterimage

fatiguing one or the other of the opponent-processing visual cells. if you stare at the color long enough, you will fatigue it and therefore when you look at a white surface (where all wavelengths can be seen) the opposing color is perceived.

JESUS!

color blindness

the lack of one or more type of cone; makes it impossible to distinguish between paired colors

red/green → common

blue/yellow → rare

audition (hearing)

humans can detect between 20 Hz and 20,000 Hz sound waves

outer ear

• external ear flaps

• auditory canal

• tympanic membrane (eardrum)

middle ear

• three smallest bones in the body

  • hammer

  • anvil

  • stirrup

inner ear

• cochlea

• oval window

• basilar membrane

cochlea

snail-shaped, fluid-filled tube that contains the receptors and structures necessary for hearing

oval window

a thin membrane at the base of the cochlea; the stirrup strikes the oval window and causes it to vibrate

basilar membrane

membrane that “floats” in the middle of the cochlea; contains the hair cells.

hair cells

tiny receptors in the inner ear that change sound waves into electrical signals (action potentials) when they bend.

place theory

LOCATION

pitch is determined by where the vibration occurs of basilar membrane.

compares hearing pitch to strings on a piano

best describes how we hear high frequency sounds (high pitches)

basilar membrane is is narrow and stiff at the base and wide and floppy at the the terminal end

frequency (temporal) theory

RATE
basilar membrane vibrates at frequency of sound wave

fore example a 50 Hz sound would cause 50 action potentials

best for lower frequency sounds (up to 100 Hz)

2 major types of deafness

• nerve deafness (sensorineural hearing loss)

• conduction deafness

• nerve deafness (sensorineural hearing loss)

damage to on or multiple:

• hair cells

• auditory nerve

• temporal nerve

**if damage is in the hair cell, a cochlear can help

conduction deafness

mechanical failure

• eardrum

• middle ear

**in case of conduction deafness, hearing aids can help amplify sound waves

the chemical senses

• smell

• taste

sense of taste is also called

gestation

taste (gestation)

much of it involves the sense of smell

no smell → taste not right

papilla

structures on the tongue which contains taste receptors (taste buds)

number of taste receptors (buds) in humans

2,000 - 10,000

6 major tasted

• sour - acids

• salty - sodium

• sweet - calories

• bitter - poisonous

• unami (savory) - proteins

• “fatty”

sense of smell is also called

olfaction

olfactory (smell) cells

cells in nasal cavity that detect odor by responding to moleculres that carry smell information

humans have about

• 5 million cells

• arranges on about 1,000 different receptor types

• and can respond to about 10,000 smells

olfactory information is sent to

hypothalamus, other limbic system structures, and prefrontal lobe

this is why our sense of smell is so closely tied to memory and also why why the emotions evoked by smells can be “unconscious”

prefrontal lobe: lets us consciously use smell (expert wine testers, for example)

vomeronasal organ

an area in the nasal cavity that has receptors sensitive to pheromones

pheromones

chemicals released by an organism that acts on other organisms of that species to produce specific behavioral or physiological responses

• reproduction

humans and pheromones

we secrete steroid molecules that resemble pheromones of other species in structure, and we have a vomeronasal organ, but we don’t know if we use it.

• we can identify individuals by smell

• women who live together often begin to onset menstrual cycles

• women who sleep with the same male over time ovulate more regularly

touch is also called

somatosensory system

somatosensory system (touch)

the bodily senses; discriminate touches

doesn’t have receptor cells that pass information to the sensory neurons; rather, the dendrites of the neurons involved in the somatosensory system transduce physical energy to neuron energy themselves.

division of the somatosensory system

• touch

  • itch/tickle

  • touch

  • flutter

  • vibration

• temperate

  • cold

  • warm (NO HOT)

• pain

• proprioception (of body)

  • position

  • movement

the sensation of pain

located throughout the entire body (but not in the brain itself!)

has motivational properties - remove ourselves from or avoid painful situations

effects and is affected by psychological processes

3 areas of the brain that seem to be involves in human experience of pain

• somatosensory cortex

• limbic system & insular cortex (in frontal lobe)

• prefrontal cortex

somatosensory context

involved in the location and descriptive qualities of pain

limbic system & insular cortex

(in frontal lobe): involved in the motivational aspects of pain

(AVOIDANCE of painful stimuli)

prefrontal cortex

involved in anticipating painful events and worry about pain

phantom limb pain

experiencing pain in a limb (arm, leg, finger, etc.) that is no longer part of the body; may be due to a reorganization of somatosensory areas responsible for the missing limb.

modulating pain

endorphins (internal morphine)

released by the periaqueductal grey in the midbrain which blocks pain information from reaching the cortex

kinesthetic sense

movement of body through space

proprioception

movement of joints & body position

vestibular sense (equilibrium)

monitors head movements; involved in experiencing dizziness

principles of perceptual goruping

stated by Gestalt physiologists, thought to be an innate predisposition of our nervous system to organize senosry input in particular ways.

figure/ground

principle proposed by Gestalt psychologists, figure/ground refers to our innate organization of objects (figures) against a background (ground).

We see them as two separate thing seeing the figure as the focal point and the ground as everything else that surrounds it.

proximity

elements that are close together → belong to same object

elements that are far apart → belong to different opbjects

similarity

elements that physically resemble each other → same object

disparate elements → belong to different objects

closure

we tend to fill in gaps in borders, because objects are perceived to be completely enclosed by borders

continuity

lines tend to be perceived co in smooth, continuous patterns, rather than oddly-shaped turns and angles

common movement (common fate)

features that move together are grouped together

depth perception

refers to seeing objects in 3D. this allows us to judge distance.

2 sets of views give us information about depth

• binocular cues

• monocular cues

binocular cues of depth

involving two eyes

retinal (binocular) disparity

each eye, because they are separate and angled slightly differently, recieve visual information at different locations.

greater angle difference → closer the object

smaller angle difference → further the object

eye convergence

reflects how much the eyes needs to come together (or converge) to focus on object.

greater convergence → closer object

eye convergence is not very useful unless object is fewer than a few feet away.

monocular cues of depth

only require one eye

these cues have been used for centuries in art to create sense of depth using only two dimensions

interposition (occlusion)

closer objects block the objects located behind them

linear perspective

parallel lines converge (come together) in the distance

texture gradient

closer objects have more texture; objects further away appear smoother

relative size

when viewing objects approximately the same size, the one creating the larger retinal image is closer

relative height

when viewing objects on a horizontal plane, objects that appear lower on the plane are closer, objects higher on the plane are further away

relative brightness (shadowing)

the use of shadowing can be cue to distance

relative clarity (aerial perspective)

objects in the distance appear “fuzzy” and bluer

motion parallax

head movement

objects closer tend to move “faster” than objects in the distance

constancies

objects retain their shape, size, color, and brightness, even if the actual image on the retina is distorted

illusion

the perceptual illusions play on depth cues and constancies

5 famous illusions:

• ames room

• muller-lyer illusion

• poggendorf illusion

• ponzo illusion

• moon illusion