Sensation and perception Flashcards
What are our senses
vision hearing, touch, smell, taste, temperature, pain, acceleration & body composition
what is the function of the vision perceptual system
Object identification/recognition & navigation & motion perception
what is the function of the visual perceptual system
Object identification/ recognition & object localisation
what is the function of the touch perceptual system
Object identification/ recognition & pain (detection of tissue damage)
what is the function of the touch perceptual system
Object identification/ recognition & pain (detection of tissue damage)
what is the function of the smell & taste perceptual system
chemical detection/ identification & nutrition & poison avoidance
what is a distal stimulus
physical object in environment
what is a proximal stimulus
a representation of the distal stimulus
what is a receptor process
the transformation of environmental physical energy into electrical energy (aka transduction)
what cells are responsible for carrying out transduction
receptor cells
how does transduction occur in vision
receptors in the retina transform light into electrical impulses
how does transduction occur in audition
receptors in the inner ear transform sound into electrical impulses
what is neural processing
the transmission of electrical signals from one neuron to another
what is perception
conscious sensory experience
what is recognition
placing an object in a category
what is action
movement of the eyes, head and body
what is top down processing
processing based on prior knowledge/experience
what is processing based on incoming sensory information known as
bottom-up processing
does perception require top down processing, bottom-up processing, both or neither
it requires both top down and bottom up processing
what is top down processing important for (in general)
helping simplify complex perceptual processes
imaging is a physiological way of recording brain activity
Name 3 types of imaging
- fMRI
- MEG
- EEG
- PET
name 3 phsyiological ways of studying whats going on in the brain during perception
- studying anatomy
- recording brain activity
- micro stimulation
- lesioning & TMS
What are psychological approaches to studying perception useful for
measures the relationship between stimulus & perception
what is an absolute threshold
the smallest magnitude we can perceive
what is difference/discrimination
1
the smallest difference we can percieve relative to the baselines level (this is not a constant value)
what are the two main approaches to studying perception
1
physiological & psychological
what is psychophysics
1
using carefully controlled experiments to test perceptual performance
what is light
2
form of electromagnetic energy
what is light physically defined by
wavelength and intensity
what is light physiologically defined by
colour and brightness
how large is the pupil
between 2-9mm diameter
how much focusing power does the cornea have
80%
how much focusing power does the lens have
20%, but can change shape due to action of cilliary muscles
how does the eye accomodate to focus on close objects
lens becomes fatter (blurs far objects)
how does the eye accomodate to focus on far objects
lens becomes thinner (blurs near objects)
what is myopia
nearsightedness
what is farsightedness
hyperopia
what is the retina
a thin photosensitive layer at the back of the eye
what are photoreceptors and what do they carry out
they are light sensitive cells and they carry out transduction
how many rod cells do we have and when are they most useful
120 million. Most useful at night & respond well to dim
what kind of vision do rod cells produce
monochromatic
Both cone and rod cells have mesopic sensitivity
what kind of sensitvity is unique to rod cells & unique to cone cells
scoptic - unique to rod cells
photopic- unique to cone cells
what is purkinje shift
at night, red looks darker than green
how many cone cells do we have and when do they work best
6 mllion, work best in daylight, not as sensitive as rods
in what order does light pass the cells in the eye
- ganglion
- amacrine
- bipolar
- horizontal
- cone cells
- rod cells
- pigment epithelium
what are the 3 types of cone and to what wavelengths of light do they respond
Red (long wavelengths)
Green (medium wavelengths)
Blue (short wavelengths)
after 20 minutes in darkness, what happens to our eye sensitivity?
increased by around 100,000x greater than sensitivty in light
do rods or cones have greater acuity and why
cones have greater acuity as they have lower convergence (6 cones per 1 ganglion cell ) (120 rods per 1 ganglion cell)
what kind of cells are in the fovea and what does this mean for its acuity
only cone cells therefore fovea has the highest acuity
when looking directly at an image, where does it fall in the eye
the fovea
what is the ratio of photoreceptors to ganglion cells
3
126:1, far fewer ganglion cells
what do ganglion cells do
condense raw info from photoreceptors & aim to extract important info from retinal image
what happens during a single cell recording
The stimulus is presented to the animal
The activity is recorded from the ganglion cell
The activity is measured over time
what are experimenters trying to find when they do a single cell recording on a ganglion cell
a stimulus that changes the activity of the ganglion cell from baseline
what does an increase in response for a ganglion cell mean
an increase in frequency of action potentials
what is a receptive field
the area on the retina which when stimulated by light, elicits a change in the firing rate of the cell
what are the two regions of a receptive field
one leads to an excitatory response, the other an inhibitory response
what is lateral inhibition
inhibition transmitted across the retina by horizontal & amacrine cells
what do the receptive fields of all ganglion cells cover
together they cover the whole visual field
do receptive fields of neighbouring ganglion cells overlap
yes
are photoreceptors part of the receptive field of only one ganglion cell
no they are part of the receptive field of multiple ganglion cells
what are ganglion cells ideal at detecting
spots of light & edges, unable to detect orientation of bars of light
if a receptive field has an on-centre, off-surround, what type of light source would cause the greatest excitatory response
stimulation of the On centre alone
what is the helmholtz illusion explained by
lateral inhibition. When the receptive field is at the intersection, more light falls on the off region so it receives more inhibition and the cell fires less
what do receptive field sizes vary with
Eccentricity: The distance between the receptive field center of a given neuron and the center of vision
what forms the optic nerve
4
bundling of ganglion cells
what is the optic chiasm
a cross over point
what is the optic tract
what the optic nerve becomes beyond the optic chiasm
what does the optic tract feed into
the Lateral Geniculeate nucleus (LGN)
what kind of structure is the Lateral geniculate nucleus
bilateral (one in each hemisphere)
what is the LGN ideal in doing
detecting spots of light & edges, not able to detect orientation of bars & edges
where does V1(aka primary visual cortex aka striate cortex) recieve its input from
LGN
what is the primary visual cortex also known as
V1/Striate cortex
what do V1 cells respond best to
lines of a particular orientation, prefers them to spots
What does retinotopic mapping mean
forms a map of the entity/object falling on the retina
what is cortical magnification and what does it state about the fovea
Amount of cortex devoted to representing each part of the retinal field is distorted
Fovea represented by large area of cortex
what are the cells in the LGN like
monocular - respond to input from left or right eye but not both
what are 80% of the cells in V1 like
binocular - respond to input from both eyes
what is ocular dominance
the fact that most ocular cells respond better to one eye than the other
what are the 3 different types of receptive fields in V1
hint: the naming progression is logical
simple cells, complex cells, hypercomplex cells
what is special about simple cells
they all have a prefered orientation
what are edge detectors
simple cells with one excitatory and one inhibitory region
what is special about complex cells
respond best to moving oriented bars and edges in a particular direction of movement
what is special about complex cells
respond best to moving oriented bars and edges in a particular direction of movement
what do hypercomplex (aka end-stopped) cells respond best to
bars of particular orientation
Moving in a particular direction
Particular length
what is the ‘what ‘ stream important for
discriminating and recognising objects
where does the ‘what’ stream travel
ventrally to inferotemporal cortex
what is the ‘where’ stream important for
determining where an object is and how to act upon it
where does the ‘where’ stream travel
dorsally to posterior parietal cortex
what lesion study provides evidence for the what and wear streams
monkey lesion study
what neuropsychological evidence is there for the what and where stream
visual form agnosia - damage to what stream
optic ataxia- damage to where stream
are the what and where streams completely seperate
no, there are many connections between them
in an experiment showcasing babies depth perception, what were the results
all the babies went to their mothers at the shallow end of the pool
none of the babies went to their mothers at the deep end of the pool
what do oculomotor cues depend on
our ability to sense the position of our eyes and tension in our eye muscles
what is convergence in reference to oculomotor cues
eye muscles causing your eyes to look inward
what is accommodation in reference to oculomotor cues
lens bulging to focus on a near object
when are cues effective
at a distance closer than 5 feet
what are pictorial cues
monocular cues - can be depicted in a still image and do not require viewing with both eyes
what is an example of a pictorial cue
Watching TV, photos, paintings
what is size constancy
2 acceptable definitions
The retinal size of objects gets smaller as they get further away.
OR
The retinal size of objects gets larger as they get closer
As objects get further away, they get nearer the horizon - what is this an example of
relative height
what does emmets law state
objects that generate retinal images of the same size will look different in physical size if they appear to be located at different distances
(think of a far away car compared to a close)
why do distant objects appear less sharp
there is more air and particles to look through (atmospheric perspective)
what is an example of linear perspective
parallel lines converging as the get further away
Is the retina curved or straight
curved
what is motion parallax an example of
a movement-produced cue
what is motion parallax
observer moves relative to a 3-d scene, nearby objects appear to move rapidly whereas far objects appear to move slowly
what is binocular disparity/ stereopsis
a cue depending on two eyes & the fact that out eyes see the world from slightly different positions
What is a corresponding retinal point
for every point on one retina, there is a corresponding point on the other retina
what is a non-corresponding retinal point
points on each retina that do not correspond to each other
as an object is moved further away is there more or less binocular disparity
less binocular disparity
at what point is there no disparity between the location that the stimulus falls on in both retina
the fixation point, as that is where both fovea are focused
what are some examples of things that show depth
virtual reality
stereograph cameras
shutter glasses
what are some examples of other species of mammal that have trichromatic vision
catarrhine monkeys
platyrrhine monkeys (only the females)
some tropical fish and birds have 4 types of colour vision, what is this called
tetrachromy
what kind of animal is pentachromatic
pigeons
What does scene segmentation mean (colour)
variations in colour often signal object boundaries
what is perceptual organisation
our visual systems using colour to group elements in a scene
what are the psychological attributes of light
hue (colour), brightness (perceived intensity) & saturation (how much colour)
what is the difference between pink and red
saturation
what is (usually) the difference between dark and light blue
intensity
what is the difference between red and blue
hue (wavelength)
What does the Young-helmholtz trichromatic theory hypothesise
that there are 3 diff receptors that respond best to diff wavelengths of light (red, green blue)
what are the rough numbers for short, medium and long wavelengths
short-420
medium- 530
long-580
what evidence is there to support the trichromatic theory of evoloution
3 primary colours combine to produce all possible colours
3 forms of dichromatism (colour blindness)
what is the opponent process theory of colour
that there are 3 processes which are opponents in nature Red-green
Yellow-blue
Black white
why did Hering come up with the opponent process theory of colour
when asking people to pick out ‘pure’ colours from a large sample, people chose red blue green AND yellow + unclear how trichromacy could explain after images
what evidence is there for opponent process theory
Non existence of certain colour combos (e.g blueish yellow)
Colour confusions in colour blindness (red and green)
Complementary afterimages
Colour context effects
at what level is the tricromacy theory of colour correct
at the level of the cones
at what level is the opponent process theory of colour perception correct
at the level of the LGN & cortical cells
What is an Anopia and what are the three types
insensitvity to L,M or S wavelengths of light due to missing a type of cone
protanopia- missing L cone
deuteranopia- missing M cone
Tritanopia- missing S cone
Only one of the 3 Anopias is more prominent than females than males, which is it
tritanopia
Only one of the 3 Anopias is more prominent than females than males, which is it
tritanopia
What are anomalies (in reference to colour perception) and what are the two types
missalignment of L or M in trichromats
Protoanomaly: L-cone pigment deficiency:
Deuteranomaly: M-cone pigment deficiency:
which colour vision theory does colour blindness support
both, anopias point to 3 cone types
Are there any animals that lack motion perception
No, all animals have some degree of motion detection/ perception
what do random dot kinematograms (RDK’s) suggest
we do not need to be able to recognise an object in order to see it move
What is the correspondence problem highlighted by
random dot kinematograms,
when do we detect movement
when the eyes are stationary and an image moves across the retina
what does a reichardt detector detect
movement of a specified direction and speed
in regards to movement detection, what do excitation and inhibition interact to create
a cell that only responds to movement from right to left
for a reichardt detector, if something moves in the proper direction, what happens
the two signals meet at the same time and this causes a strong response
for a reichardt detector, when something moves in the wrong direction, what happens
there is no response
for a reichardt detector, when something is moving too fast
the timing is off so there is no response
in a reichardt detector , what happens if you make a bigger separation between the two detectors
they detect faster motion as the changing of the detectors measures different speeds
what does velocity transposition show
two images moving across the visual field at diff speeds can be perceived moving at the same time
what things affect the threshold potential for movement detection
the object and its surroundings
what is the requirement for a cat in a larger cage to be percieved as mocing at the same speed as a rat in a smaller cage
the cat has to move faster
what things give evidence to helmholtz outflow theory
afterimages when we move our eyes
world moves when we passively wobble eyes
what is ‘Afterimages move when we move our eyes’ an example of
eye muscle movement signal, no retinal movement
what is ‘World moves when we passively wobble our eyes’ an example of
retinal movement, no eye muscle movement signal
what is apparent/stroboscopic movement
Illusion of movement between two lights by flashing one on & off, waiting 40-200 ms, then flashing other light on & off
(think of Harpers play)
when two lights are shone 30–60 msec apart, when movement is this an example of
partial movement
when two lights are shone Around 60 msec apart, when movement is this an example of
optimum movement
when two lights are shone 60-200 msec apart, when movement is this an example of
beta & phi movement (phenomenon)
what is beta movement
movement appears to occur between lights but it is difficult to actually perceive an object moving across the space between them
(literally just the opposite of phi movement)
what is phi movement
perceive an object between two lights being shone 60-200 msec apart
when two lights are shone Above 200msec, when movement is this an example of
there is no movement, they are successive
what is induced movement
surrounding a spot with another object and moving said object
what is autokinetic movement
Turn off all room lights, when surrounding framework is not visible, small stationary light appears to move, usually in erratic path
what are the characteristics of a soundwave
frequency, amplitude and complexity
what do long wavelengths and short wavelengths mean frequency wise
short wavelegnth = high frequency = high musical note
long wavelegnth = low frequency = low musical note
what is frequency perceived as
pitch
what do high and low amplitude mean and what is amplitude percieved as
perceived as loudness
high = loud
low = quiet
what is complexity percieved as for a soundwave
timbre/sound quality
what does fundamental frequency mean
the wavelength of the longest component determines the pitch of the sound
what do harmoics determine
sound quality/timbre
what is the vestibular system important for
balance
what structures is the vestibular system made up of
semicircular canal, endolymph, cupula & nerves
what happens in the middle and inner ear
eardrum vibrates, causing ossicles to move,
why do we sound different when our voices are being recorded/played back to us
skull and jaw vibrate when we move so we hear our own voice conducted through the bones of our skull
what vibrates to produce a wave in the basilar membrane
oval window
what is the shape of the wave in the basilar membrane dependent on
frequency of the sound
the ear is a frequency analyser, what does this mean
based on how sound waves travel in the ear, it determines the frequency of the sound and allows us to hear the correct pitch
what structures do the cochlear have which detect vibrations in the basilar membrane
hair cells
when do hair cells change their firing rate
when they are bent
how small of movements are hair cells sensitive to
as small as 10 picometers
hair cells are tonotropic, what does this mean
they respond preferentially to particular frequencies
what are the stages/the process of auditory transduction
Air pressure changes (kinetic)
Vibration of eardrum → middle ear → oval window (mechanical)
Cochlear fluid flows (kinetic)
Hair cells bend (mechanical)
Auditory nerve fires (neural)
are pitch and loudness independent
no, More intense low frequency sounds are perceived as a lower pitch
what is binaural (two ear) space perception needed to perceive
direction of where an auditory stimulus is coming from
under what sort of auditory perception do you get the doppler effect
monaural (sound that originates from one location)
what does the head shadow effect refer to
the attenuation of sound, sound must travel further to reach the left ear (if the stimulus comes from right side) so diffuses around head
what are the 3 streams auditory infomation is grouped into
space
time
frequency
what are sherpard tones
sounds of the same pitch which have the appearance of going in an ascending scale
who said ‘The study of what are called illusions of the senses is a very prominent part of the senses; for just those cases which are not in accordance with reality are particularly instructive for the discovering the laws of those means and processes by which normal perception originates”
helmholtz
why do visual illusions occur
Sometimes ‘perceptual hypothesis’ is incorrect and an illusion is resultant (Gregory,1997)
Illusions occur when what we see does not correspond to what is physically presented
what are the 4 classifications of visual illusion
distortions
ambigious figures
paradoxical figures
fictions
what are some examples of distortion visual illusions
Muller-lyer, ponzo, poggendorff, hering & Wundt
what are some examples of paradoxical figure visual illusions
impossible objects
what are some examples of ambigious figures visual illusiosn
necker cube, rubin vase
what are some examples of fictions visual
kanizsa triangle, ames room
what is the muller-lyer illusion
two straight linesofthe same size , one with inward facing fins and one with outward facing fins, the outward fin line looks longer/further away
does the muller lyer illusion apply to everyone
not cross cultural: people who live in natural environments (w/o man made rectangle structures) are much less prone to the illusion
what is the ponzo illusion
Illusion of size : two lines converge towards vanishing point - gives impression the line nearer the vanishing point is further away, so appears larger
what is the necker cube illusion
is the dot in the cube in the close or far corner
what is a kanisza triangle and why does this illusion occur
a ‘subjective contour’ which occurs because near objects look brighter distant ones of the brain interprets the illusory triangles as being closer than the circles. This means you see them as being brighter than the things that you think are further away
what do moon illusions affect perceptually
size, moon looks bigger on horizon compared to zenith
what do the ouchi illusion and peripheral drift illusion affect perceptually
motion perception, brain interprets that there must be movement due to diff pattern orientations
The skin is the largest organ in the body, what is its area and mass
Area = 1.8 m2
Weight = 5 Kg
What are the two types of skin?
Glabrous (found on palms of hands and feet) and hairy (found everywhere else).
What are the two types of skin?
Glabrous (found on palms of hands and feet) and hairy (found everywhere else).
What happens when a stimulus contacts the skin?
A receptor in the skin fires, and the signal travels to the brain via the spinal cord until it reaches the somatosensory cortex on the opposite side of the body.
What are the four senses, that receptors sensitive to many kinds of energy, give rise to?
Touch, pain, body sense (proprioception), and temperature.
What are the four types of tactile receptors in the skin, and in what order are they from closest to the surface to deepest embedded?
Merkel’s disc (fine details), Meissner corpuscle (fluttering sensation), Ruffini organ (stretching), and Paccinian corpuscle (vibration and fine texture).
what is important about having many different receptor types
Many receptors detect many types of information, and a single stimulus can activate many different receptor systems.
What are receptive fields?
The area of skin that a particular cell receives information about.
What is the two-point threshold?
The smallest separation of two separate but adjacent points of stimulation on the skin that just produces two distinct impressions of touch.
What are some advantages of active touch?
More parts of the body can contact an object, the most diagnostic parts of objects can be felt, and kinesthetic senses are also engaged.
what is the two point threshold on the fingertip compared to the arm
2mm on fingertip
3.5cm on arm
What are the two types of pain?
Fast pain (sharp, A delta fibers) and slow pain (dull, C fibers).
What can pain be affected by?
A person’s mental state, the absence of stimulation, and attention.
what is the emotional effect on the top down influence on touch
same sensation may be pleasurable or unpleasant
what is the ratio of receptors on our fingertips compared to our backs and what affect does this have on two point threshold
We have 100 times more receptors per square cm on our fingertips than on our back
decreased two point threshold
How can pain be reduced
non-painful tactile inputs, top-down input, and interneurons that can inhibit the synapses to the spinal cord to prevent pain sensations.
What is proprioception?
Where the body is in space, as signaled by muscles, the vestibular system, tactile receptors, and kinesthesis.
What did IW lose due to a viral infection at age 19?
Proprioception, kinesthesis, and touch.
What is the function of the cornea?
acts as a protective covering and helps to focus light.
What is the function of the lens?
helps to focus light and adjust the shape of the eye for near or far vision.
what are the 5 core tastes
sweet, sour , salty, bitter & umami
where do the 5 core tastes correspond to location wise on a taste map
trick question, taste maps are bullshit
what causes sugar tastes
sugars (fructose, glucose…), artificial sweeteners (aspartame, saccharin…)
what causes sour tastes
all acids ( acetic, citric, ascorbic, phosphoric, lactic …)
what causes bitter tastes
no unique chemical class ; quinine, caffeine, peptide, phenols
what causes salty tastes
salts like table salt (NaCl) or NH4Cl, KCl
what causes umami tastes
mono sodium glutamate Inosine 5’ - monophosphate, guanosine 5’-monophosphate
(MSG)
what are the differences between super tasters and hypotasters
Supertasters have more papillae & taste buds
Hypotasters have less papillae & taste buds
(compared to average )
what is a potential ‘sixth’ taste
starch
how many different molecules can we discriminate via smell
1 Trillion
what are the top down effects on smell
Attention
Sniffing (if youre smelling to see if something is burning)
Automatic attention (if someone farts and it stank asf)
Effect of labelling
E.g same odours smells worse when labelled as body odour vs as cheese
Effect of learning
E.g expert wine tasters identifying wine odours
proust effect is? ( smell and memory)
vivid being memories brought back by particular smells
what is the limbic system closely linked to
smell
what is an example of multisensory perception
eating, flavour activates taste and olfaction
what things influence taste
texture, pain(e.g chilli’s), sound (crunch) and vision
imagine you just ate a chilli, what tastes have effects on suppressing the ‘pain’ experienced
Best- sweet and sour liquids (milk is defined as sweet)
Bitter is not effective in suppressing spice/chill
Salty flavours are intermediates in suppressing chilli/spice
what is a multisensory stimulus
generates several independent energies, which are simultaneously detectable by diff types of sensory receptors’ (Meredith, 2003)
what is special about single neurones in multisensory receptive fields
may respond to more than one modality
what is the mcgurk effect
Watch lips go ga-ga
Hear sound ba-ba
Subjects perceive movement da-da
Visual info is affecting the sound that you hear
what is kinaesthesia
illusion of speed
Nervous system turns down the ‘gain’ on steady-state inputs
If youre going 70mph, 10 mins later after steadily gfoing at 70mph, it feels like 50mph
what is synaesthesia
Stimulation of a particular type which always leads to another perceptual experience
