4 - Sensation and Perception Flashcards
Sensation
simple stimulation of a sense organ; basic registartion of light, sound, pressure, odor, or taste as parts of your body interact with the physical world
Perception
the organization, identification, and interpretation of a sensation in order to form a mental representation
transduction
when many sensors in the body convert hysical signals from the environment into encoded nerual signals sent to the central nervous system
Psychophysics
methods that measure the strength of a stimulus and the observer’s sensitivity to that stimulus
Absolute threshold
minimal intensity needed to just barely detect a stimulus in 50% of the trials; a boundary
JND
just noticable difference; the minimal change in a stimulus that can just barely be detected
Weber’s Law
The JND of a stimulus is a constant proportion despite vatriations in intensity. ex: 1 ounce envelope vs 2 counce envelope, will be felt; 20 pound package and 20 pound 1 ounce package, will not be felt
Signal detection theory
the respones to a stimulus depends both on a person’s sensitivity to the stimulus in the presnse of noise and on a person’s decision criterion
hit, miss, false alarm, correct rejection
light + yes = hit
light + no = miss
no light + yes = false alarm
no light + no = correct rejection
perceptual sensitivity
how effectively the perceptual system represents sensory events
selective attention
only percieving what;s currently relevant to you
why can’t you text and drive?
selective attention, multitasking; phone conversations require memory retrieval, deliberation, planning, emotion, and take much more attention than, say, listening to the radio. impairing of texting has been found to be equal to alcohol consumption and greater than marjuana
sensory adaption
sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions
visual acuity
ability to see fine detail
length of light
hue/colour
amplitude
brightness
purity
(number of distinct wavelenghts that make up the light) saturation/richness
Cornea
clear, smooth outer tisue, bends light wave and sends it through the pupil
pupil
hole in coloured part of eye
iris
coloured part of the eye, translucent, doughnut shaped muscle, controls the size of the pupil
retina
light sensitive tissue lining the back of the eyeball
accommodation
the process by which the eye maintains a clear image on the retina
myopia
eyeball is too long, images are focused in front of the retina, nearsightedness
hyperopia
eyeball is too short, images are focused behind the retina, farsightedness
photoreceptor cells
cones, rods
cones
colour, operate under normal daylight conditions, allow us to focus on fine detail, 6 million
rods
active under low light onditions for nightvision, more sesntive to cones, provide no information about colour, only shades of grey, 120 million
fovea
an area of the retina where vision is clearest and there are no rods at all
explain how the fovea affects how we see
night sky
bipolar cells
collect neural signals from the rods and cones and transmit them to the outermost layer of the retina
RGCs
retinal ganglion cells, organize the signals and send them to the brain
blind spot
a location in the visual field that produces no sensation on the retina
colour deficiency
colour blindness, genetic, one or more of the cone types is missing
colour afterimage
staring too long at one colour fatigues the cones that respond to that colour, producing a form of sensory adaption that results in an afterimage
colour opponent system
pairs of visual neruons work in oppositive, red senstivie against green sensitive; blue sensitive cells agianst yellow sensitive
LGN
lateral geniculate nucleus, located in the thalamus
area V1
part of the occipital lobe that ocntains the primary visual cortex
two visual pathways
ventral (what) and dorsal (where)
ventral stream
occipital lobe –> lower levels of temporal lobe; “what” path
dorsal stream
occipital lobe –> parietal lobes (including some of the middle and upper levels of the temporal lobes), connecting brain with areas taht identify the location and motion of an object; “where” path
“where” vs “how” path
scientists argue that the dorsal stream is crucial for guiding movements like aiming, reaching, or tracking with the eyes, thus the “where’ pathway should be called the ““how” pathway
visual form agnosia
the inability to recognize objects by sight
binding provelm
how features are linked together so we can see unified objects in our visual world rather than free-floating or miscombined features
illusory conjunction
a perceptual mistake where features from multple objects are incorrectly cobined
feature-integration theory
focused attention is not required to detect the individual features that comprise a stimulus, such as the colour, shapre, size, and location of letter, but it required to bind those individual features together
modular view
specialized brain areas or modules detect and represeent faces or house or body parts
distributed representation
pattern of activity acoross multiple brain regions that identies any viewed object, including faces
perceptual constancy
even as aspects of sensory signals change, perception remains consistent
princples of perceptual organization
gestalt; simplicity, colosure, continuitiny, similiarity, proximity, common fate
simplicity
the simplest explanation is usually the best
closure
we tend to fill in missing elements of a visual scene, allowing us to percieve edges that are separated by gaps as belonging to compltete objects
continuinity
edges or contors that have the same orientation tend toward good coninuation, we tend to group them together perceptually
similarity
regions that are similar in colour, lightness, shape, or texture are percieved as belonging to the same object
proximity
objects that are close together tend to be grouped togehter
common fate
elemts of a visual image that move together are percieved as parts of a single moving object
figure
the thing that you are focusing on
ground
(back)ground; everything that you aren’t focusing on
edge assignment
given an edge, or boundary, between figure and ground, which region does that edge belong to?
Rubin vase is example of what?
reversible figure-ground relationship
Template
a mental representation that can be directly compared to a viewed shape in the retinal image
image-based object recognition
an object you have seen before is stored in memory as a template; widely accepted, yet they do not explain everything about object recognition
What’s wrong with image-based object recognition?
correctly matching images to templates suggests that you have one template for cups on their side, another for cups upside down, etc. This is unweildy and inefficient, therefore unlikely to be effective, yet seeing a cup on its side is unlikely to confuse one for long
Parts-based object recognition
the brain deconstructs viewed objects into a collection of parts. Contends that objects are stored in memory as structural descriptions: mental inventories of object parst along with the spatial relationship between these parts
What’s wrong with parts-based object recognition?
allows for object recognition only at the level of categories and not at the level of the indiviudal object. Explain why you can recognize a face from a shoe, but not why you can recognize your sister’s face from your best friend’s.
Monocular depth cues
aspects of a scene that yield information about depth when viewed with only one eye; linear prespective, texture gradient, interposition, relative height, relative size, familiar size
linear perspective
parallel lines seem to converge as they recede into the distance
texture gradient
the more detail an object has, the closer it is perceived to be
interposition
the object in front is seen as closer
relative height in the image
objects closer to you are lower in your visual filed, whereas faraway objects are higher
relative size
the smaller the object is, the farther away it is
familiar size
the brain assumes how far away a familiar object is based on its size
binocular disparity
the difference in the retinal images of the two eyes that provides information about depth
wheatstone
1838, invented the sterescope. held two photographs taken from two horizontally displaced locations and evoked a strong sense of depth. modern sucessor is teh view master
motion perception
object moves across observer’s field of sight, stimulates one location on retina, then stimulates another location on the retina. neural circuts in brain detect this change in position over time and respnd to specific speeds and directions of motion.. operates in part on opponent processes and is subject to sensory adpation.
what part of the brain is involved with motion perception?
middle of the temporal lobe refered to as MT (part of the dorsal stream)
how does the brain perceive motion when the observer is moving?
the motion perception system takes into account the position and movement of the eyes and “subtracts” them from the motion of the retinal image
waterfall illusion
stare at the downward rush of waterfall for a long time, look at a stationary object, you feel an upward motion. Motion-sensitive neurons connected to motion detector cells in the brain that encode motion in the opposite direction. If one set of motion detector cells is fatigued through adpation to motion in one dreiction, thenthe opposing sensor will take over. The net result is that motion is perceived in the opposite direction.
appart motion
perception of movement as a result of alternating signals appearing in rapid succession in different locations
change blindness
when people fail to detect changes to visual details of a scene
ex: man gives directions to someone and doesn’t notice when the man is replaced halfway through the experiment
inattentional blindness
a failure to percieve objects that are not the focus of attention
ex: unicylcing clown is noticed by non-texters, but not as much by the texters
sound waves
changes in air pressure unfolding over timw
pure tone
a simple sound wave that first increases air pressure thaen creates a relative vaccumm
frequency
pitch (how low or high sound is)
amplitude
loudness, or a sound’s intensity
complexity of sound waves
timbre, listener’s experience of sound quality or resonance
outer ear
collects sound waves and funnels them towards the middle ear. visible part on head. pinna; auditory canal, eardrum
middle ear
transmits the vibrations to the inner ear. tiny, airfilled chamber behind ear drum, contains the ossicles (hammer, anvi, stirrup), a lever that mechanically transmits and intensifies vibrations from the eardrum to inner ear
inner ear
embedded in the skull, where they are transduced into neural impulses. cochlea, basilar membrane, hair cells
cochlea
latin for snail, fluid filled tube that is the organ of auditory transduction
basilar membrane
strucutre in the inner ear that undulates when vibrations from the ossicles reach the cochlear fluid
hair cells
thousands, specialized auditory recpetor neurons embedded in the basilar membrane
area A1
area in cerbral cortex, portion of the temporal lobe that contains teh primary auditory cortex
place code
process by which different frequencies stimulate neural signals at specific places along the basilar membrane
how does the basilar membrane react to different pitches?
(apex) wide, floppy tip moves most when low frequency; (base) narrow, stiff end moves most when high frequency
temporal code
registers relatively low freqencies (up to 5000 Hz) via the firing rate of action potentials entering the auditory nerve
how do we localize hearing?
timing and stereophonic hearing (having ears on opposite sides of the head) changing the loudness comparativly in each ear
conductive hearing loss
eardrum or ossicles damaged to the point where they cannot conduct sound waves effectively to the cochlea
sensorineural hearind loss
caused by damage to the cochlea, hair cells, or auditory nerve, happens to almost all of us as we age. can be heightenied in people regularily exposed to high noise levels. amplifying the sound does not help because hair cells cannot transduce sound waves
haptic perception
active exploration of the environment by touching and grasping objects with our hands
thermoreceptors
nerve dibres that sense cold and warmth
three important principles regarding neural represntation of the body’s surface
- The left half of the body is represented by the right, and vice versa
- Just as more of the visual brain is devoted to foveal vision where acuity is greatest, more of the tactile brain is devoted to parts of teh skin surgace that have greater spatial resolution
- A lot of evidence that the distinctions between “what” and “where” pathways in touch analogous to those for vision and auditon
Touching things while shopping
the longer one touches something, the more they increase their feeling of ownership of the item and increase its value
A-delta fibres
fast acting, transmit the initial sharp pain right after sudden injury
C fibres
transmit the longer lasting, duller pain that persists after initial injury
Two parts of brain that neural signals for pain go
- somatosensory cortex, identifying where the pain is and what sort of pain it is
- motivational and emotional centres of the brain, like the hypothalamus and amygdala, and to the frontal lobe. this is the part of pain that is unpleasent and motivates us to escape from or relieve the pain
referred pain
sensory information from internal and external areas converge on the same nerve cells in the spinal cord. ex: pain in left arm during heart attack
turf toe
pain in base of big toe as result of pushing off or bending repeatedly
gate control theory of pain
signals arriving from pain receptors in the body can be stopped, or gated, by interneurons in the spinal cord via feedback from two directions
ex: rubbing stubbed toe makes pain “go away”
PAG
periaqueductal gray, grey matter in region of midbrain taht plays role in teh decension of pain modulation and defnsiveness.
feedback signal that decreases pain
under extreme condition like high stress, naturally occuring endorphins can activate the PAG to send inhibitory signals to neurons in the spainl cord that then suppress pain signals to the brain, thereby modulating the experience of pain
feedback signal that increases pain
activated by events such as infrection and learned danger signals. When we are quite ill, what otherwise might be experienced as mild disomfort can feel quite painful. presumably evolved to motivate people who are ill to rest and avoid strenuous activity, allowing their energy to be devoted to healing
vestibular system
the three fluid filled semicircular canals and adjacent organs located next to the cochlea in each inner ear
why is an important aspecct of sensation and perception knowing where parts of the body are at any given moment?
your body needs some way to sense its position in physcial space.
Somatosensation
all about physiccal changes in or on the body. vision, hearing, touch, smell, taste
olfaction
least understaood sense, only one directly connected to the forebrain, w/ pathways into the frontal lobe, amygdala, and other forebrain structures.
why did smell evolve?
signalling sense for the familiar: friendly creature, edible food, sexually receptive mate
how do substances release odors into the air?
odorant molecules, driftingi in the air
olfactory epithelium
mucous membrane situated along the top of the nasal cavity, contains 10million ORNs
ORNs
olfactory receptor neurons; receptors cells that intiate the sense of smell
olfactory bulb
a brain structure located above the nasal cavity beneath the frontal lobes. humans have about 350 different types that permit us to discriminate among 10 000 different odorants through unique patterns of neural activity each odarant evokes.
humans are sensitive to some smells in extremeley small concetrations
gas: 0.0003 parts per million, but nail polish remover only 15 parts per million
object-centref approach
information about the identity of the “odor object” is quickly accessed from memory and then triggers an emotional reponse
valence-centred approach
the emotional response comes first and provides basis for determining the identity of the odor
pheremones
biochemical odarants emitted by other members of its species that can affect the animal’s behaviour or physiology
papillae
easily visible to the naked eye, bumps that cover the tongue
taste buds
hundreds in each papilla, the organ of taste transduction. mouth contains 5 000 to 10 000 taste buds fairly evenly distributed over the tongue, roof of mouth, and upper throat. each taste bud contains 50 - 1000 taste receptor cells.
taste reception doesn’t fade over time
True or false?
flase. on average, people lose half their taste rceceptors by the time they turn 20. this may explain how young children tend to be fussy eaters, since their greater number of taste buds bring with it a greater range of taste sensations
5 main types of taste receptors in the taste system
slat, sour, bitter, sweet, unami (savoury)
microvilli
tips of taste receptor cells that react with tastant molecules in food
salt taste receptors most strongly activated by ____
sodium chloride, or table salt
sour receptor cells respond to ____
acids, such as vinegar or lime juice
bitter taste receptors activated by ___
50 - 80 different bitter-tasting chemicals actiavte equal number of distinct binding sites in bitter receptors
sweet receptor cells are activated by _____
wide range of substances in addition to sugars
umami receptor cells respond most strongly to _____.
flutamate, amino acid in many protein-containing foods. It is an excitatory neurotransmitter.
MSG
monosodium glutamate is often used to flavour Asian foods
tasters, nontasters, supertasters
tasters - mild bitter taste in caffeine, saccharine, certain green vegetables, and other substances
nontasters - no bitter taste
supertasters - extremely bitter to the point of being inedible (esp. green vegetables). Children start as supertasters or tasters, can grow up to be nontasters. supertasters avoid green vegetables, which puts them at risk for diseases like colon cancer, but they also avoid some fatty foods so they are thinner and at less of a risk for cardiovascular diseases
charles bonnet syndrome
the experience of complex visual hallucinations in a person with partial or severe blindness, found commonly in elderly people with bad vision.
