perception Flashcards
differentiate perception from sensation
perception involves INTERPRETING sensation
6 senses of perception
vision
hearing
somatosensation - awareness of the body in space
taste
smell (olfaction)
vestibular - inner ear senses gravity + movement
define qualia
subjective, qualitative aspects of conscious experiences, can’t be directly articulated, WHAT IS IT THAT EXPLAINS PHENOMENOLOGICAL EXPERIENCES THAT ARE DIFFERENT, how does the brain know what is causing the stimulation it receives
grapheme-color synesthesia
letters and/or numbers always involuntarily associated with a specific colour
cafe wall illusion
‘grid’ lines actually horizontal but look all wonky
rotating snake illusion
when you move your eyes, contrast between two colours simulates a false sense of motion
checker-shadow illusion
squares marker A and B are same shade but look like not
* B receiving less light in the image so contrastingly we think it’s lighter –> we use shadows as context clues
troxler fading
stare at x, cat face disappears, –> activated receptors for colours get lazy
pink dots
blank space turns into a singular green dot, pink dots fade
what do illusions reveal
active processes the brain deploys to interpret images, reveals general rules about visual system to make guesses/inferences about physical world
dimensionality problem
there are to many diff chemicals to have receptors for each - we condense to biologically relevant dimensions (5 for taste, 400 for smell)
papillae
give tongue bumpy appearance, cover whole tongue and include bundles of fibres containing each taste receptor
primary taste sensations + what they sense
sweet: energy rich nutrients (carbs, sugar)
salty: electrolyte balance
sour: acidity
bitter: potential poison
umami: detect amino acids (MSG)
sensitivity to different tastes
most sensitive to bitter, then sour, salty, sweet. evolutionary.
supertasters
- more receptors on tongue
- more common in Asians + Africans + women
- unlikely to enjoy brussels sprouts + brocolli, coffee + fatty foods
two examples of taste not requiring presence of taste experienced
- miracle fruit - binds to taste buds, makes everything taste sweet afterwards
- pine mouth: bitter, metallic taste
what is spiciness
NOT a flavour - it’s literally just pain
babies and smell
recognises mother’s smell within weeks, suck more if senses own mum rather than stranger
shape pattern theory of olfaction
odorants would fit into odorant receptors + bind, producing smell sensation. INCORRECT - proved similar particles smelled vastly different, vastly different smelled same etc
can you ‘get better’ at smelling
yes, huge learning effects in identifying (wine training0
adaptation in smell
we adapt to our own smell, don’t notice it. more sensitive to smells that aren’t our own
importance of touch in movement
when can’t sense what ur holding it’s extremely difficult to move
two major subsystems of somatic sensory
- detection of mechanical stimuli (light touch, vibration, pressure, skin tension), monitoring internal/external forces on body at any moment
- detection of pain + temperature: detect potentially harmful circumstances
mechanosensory processing two types
EXTERNAL + INTERNAL
* detection of external stimuli
* proprioceptors - receptors INSIDE muscles, joints, other deep structures monitor mechanical forces generated by musculoskeletal system
how do receptors work for touch
stimuli applied to skin deform/change nerve endings, induces depolarising current, triggers action potentials
mechanoreceptors sense…
touch
nociceptors
pain
thermoceptors
heat
2 types of touch fibers (adapting)
- rapidly adapting: info about change/dynamical quality
- slowly adapting: info about shape, edges, texture
meissner corpuscles
RAPIDLY ADAPTING
* just beneath epidermis of fingers, palms, soles, VERY sensitive, common to hairless skin
Pacinian corpuscles
RAPID ADAPTING
gelatinous around nerve ending: feel deep pressure + vibration, looks like an onion, proprioception
merkel disks
SLOWLY ADAPTING
* in epidermis, dense in fingertips, lips, ext genitalia, light sense of pressure recepted
tactile afterimages
texture contrast –> after touching something rough, medium rough surfaces feel smoother, also for temperature
tactile adaptation
putting on a bra and not feeeling it after a while - objects on skin less noticeable the longer they’re on and not moving
active v passive touch
tactile system perceives best when it’s exploring –> when WE’RE the ones touching rather than it being touched to us
nociceptors types
terminate in unspecialised free endings, so Asigma are acute, sharp pain and C fibres are lingering, aching pain –> that’s why there’s two different waves of pain
hyperalgesia
painonly sense exhibiting enhanced sensitivity to stimuli over time
referred pain
receptors for visceral pain transmission conveyed in part centrally so pain originating in heart can manifest as well in left arm etc
thermoceptors and phys zero0
temp sensors just sense things outside physiological zero - why we can adapt to cold ocean + swim
somatosensory and motor humunculi
representation of the body along the cortex, where adjacent body areas have adjacent representations in cortex, size correlated with how much space each body part takes up in somatosensory cortex
vestibular system purpose
assist with control of gaze/posture, detect gravitational forces
semicircular canals
3 angular accelerometers within inner ear, oriented in diff directions –> filled w liquid which moves with movements and gives info about inertia
otoliths
2 linear accelorometers, UP AND DOWN movements of head
what is acceleration
any change in state of motion: velocity + accelerations are vectors w length and direction
how do you excite a vestibular hair-cell ?
bending it in its preferred direction. bending same cell in opposite direction inhibits the neuron
sicadic suppression
even though you receive motion input when you make an eye movement, you don’t feel like you’ve moved (sicadic suppression)
describe the vestibuloocular reflex
the head makes compensatory eye movements to account for head movements so that they keep tracking desired objects
ear part + function
pinna + eardrum: directional microphone
middle ear: impedance matching and overload protection
inner ear: frequency analysis
compression vs rarefaction
clapping compresses particles, makes vibration. then rarefaction in subsequent expansion of particles in space
what do you need to make sound
a medium
vibration
amplitude
percept of loudness
frequency
percept of pitch
purity
percept of timbre
perception of loudness increases how
logarithmically
equal loudness curves, what do they show?
what you have to do to each frequency to get it to be that ludness - troughs are the frequencies you’re most sensistive to
transduction - what do you need
air pressure in middle ear must be same as outer ear
ossicles
three smallest bones in human body - malleus, incus, stapes
round window purpose in ear
gives a place to bulge our when stapes bumps against
how do we impedance match
malleus + incus act like lever system, push sounds into stapes oval window to increase pressure, doesn’t reflect and goes into inner ear
3 ways to represent sound
time domain - plotting sound as time signal highlights envelope, oscillations in acoustic energy
frequency domain - plot individual frequencies,
spectogram - all frequencies w equal energy
pitch of different frequencies follows what curve
logarithmic
how is perception of pitch organized?
like a helix - wraps around to the same note an octave higher
how are instruments similar/different in sounds produced?
all produced same frequencies when played at given pitch
BUT
differ in RELATIVE AMPLITUDES
what creates timbre
amplitude of the upper harmonics/overtones
how is pitch conveyed
fundamental (lowest) frequency, and timbre of relative amplitudes of overtones
how does membrane in cochlea contribute to sensation
movement of basilar membrane = hair celles move against membrane, cilia bensd _ convert into electrochemical signal
early theory rutherford + problem
proposed whole membrane moved at once like a diaphragm
* in fact basilar membrane varies in thickness + stiffness
georg von bekesy contribution
made a crude model of cochlea w rubber membrane, found frequencies tingled different areas of arm –> frequency sensitivity changes as move along basilar membrane
for low frequencies what special property
auditory nerve spikes are phase-locked to the stimulus
cues to frequency in a sound
place of excitation in cochlea
frequency of firing
tonotopy
there;s a map of tones in the head; stimulate and you’ll hear it
surface reflectance
diffuse= strike, bounce off in every direction (matte)
specular = strike, bounce off in a single beam (shiny)
three stages for vision
- sample optical structure
- transduce light energy into electrical impulses
- transmit info to brain for interpretation
concave mirror eyes
receive info, bounce so it converges at a single point –> best at sampling only from direction it’s pointing - why clams have heaps of them
compound eye
bugs
series of light tubes funnelling light in
how do pinholes work
funnel light so thin point that every individual position in world maps onto one position in retina. brain has to flip image. oinly works in rlly bright settings
convex lens of single chambered eye
diverging light reflected from all directions converge onto single point to form image thanks to lens
myopia + hyperopia
hyperopia = long-sighted, eye too short, image forms behind eye
myopia = short-sighted, eye too long, image forms in front of eye
far vs near accommodation
far = lens flatter
near = rounder
when is the only time you can have both far and near things blurred?
if ur looking at something real close up
tilt-shift illusion
blur far and close oarts of image makes brain think you;re looking at something tiny
scotopic vision
low-light rod dominated
photopic vision
high light cone dominated
3 types of cones
long, med, short
retinal distribution of cones
rods: cones 20:1
trichromatic theory
different color experience due to activation of 3 receptor types, mix colour + overlap
why do objects appear coloured?
colour related to PROPORTIONS of RGB cone receptors. short + medium wavelengths get absorbed, longer ones get reflected
if I’m looking at an apple and it’s red, which cone is most bouncing off + reflecting?
red
opponent processes
visual system interprets colour through 3 pairs of colours, so you can’t see greenish red/blueish yellow. also explains colour aftereffects: neurons excited by red become fatigued, instead show green
anamolous trichromats
red/green colour bline - their long and medium cones overlap more than they should
