Lecture 4- Sensation & perception Flashcards
Sensation
nervous system detects or encodes information from the environments or our bodies
perception
how we give meaning or interpret what our nerve sensations are
transduction
physical energy is converted into nervous system activity
perception vs commonalities
perception is unique to a person but there are commonalities.
- we dont perceive everything in the world, we miss things and see different things that aren’t necessarily there (illusions)
Themes of perception
- depends on context
- about expectations
- is multimodal
what is light
- slither on electromagnetic spectrum (400-700nm)
- waves or photons
- objects dont emit light, light reflects off of things to make them visible (reflection)
refraction
- light passes through objects but can bend depending on the material
- ex: lenses refract light
Lens of the eye
- lens bends (refracts) to focus light onto the retina
- changes shape
retina
- in the back of the eye
- has sensory cells that transduce light
ciliary muscles
- muscle that helps change the shape of the lens
accomodation
when the ciliary muscles change the shape of the lens
unaccommodated
- when muscles are relaxed, lens in thin and flat
- unaccommodated is for seeing far away
accommodated
- when ciliary muscles are contracted, the lens is fat and thick
- to see close up objects
myopia
- nearsightedness
- object focuses in front of the retina
- eyeball might be too big for lens
solution to myopia
concave lens
hyperopia
- farsightedness
- objects focus behind retina
solution to hyperopia
fixed by convex lens (bends light inwards)
macula
centre of retina
cones
- middle of the eye
- conical shape
- used to see color and detail
- three kinds of cones
rods
- peripheral
- rod shaped
- show dark vs light
- shows motion
trichromatic theory of colour vision
you need all three cones to see colour.
it is the combination of cone activity that influences our colour vision
- blue cones respond to blue light but not only blue light.
colour contrast
- colour can depend on their backgrounds and context.
- the way we see colour can be affected by what they are in contrast to.
- the same colour can look different when compared to a light colour vs a dark colour
colour constancy
- when colour should stay the same to us even when they are seen in different lightings
- the colour we see is physically different in different lightings but our brains integrate the context and what w know about their properties so that they do not physically change in our minds.
illuminant
the lighting conditions that we understand or imagine
- our brains can expect to see certain illuminant and create shadows
- this is a reason for seeing the dress differently
Dress debate
- if you the imagine the illuminant as yellow then the dress appears as gold and white
- perception depends on context
gestalt laws
gesalt= whole (about expectation)
- proximity
- similarity
- continuity
- closure
proximity
perceive groups near each other as grouped together
similarity
perceive similar objects in groups
- can tell the difference of teams by grouping players in the same colour jersey together
continuity
perceive stimuli as single uninterrupted objects
- if a bridge is on top of railroad tracks we assume that the tracks continue under it even if we cant see it
- fill in the gaps where there are gaps in lines
closure
- perceive stimuli as whole entities/shapes even if there is something missing
- see a peacock in the nbc logo even thought its not really drawn out
monocular depth cues
only need one eye to perceive depth
- linear perspective
- relative height
- relative size
- familiar size
- aerial perspective
- motion parallex
linear perspective
parallel lines converge in the distance but diverge closer to us.
- looks like they are connecting in distance even though they continue to be parallel
relative height
faraway objects are higher in our view than closer objects
relative size
nearby objects appear larger than objects in the distance
familiar size
we have prior knowledge of the size of an and how it should appear relative to other objects
aerial perspective
distant objects appear more hazy because light is scattered by atmosphere
motion parallex
when in motion, objects that are farther away seem to be moving slower than objects that are closer to us
- difference in parallax is how we tell how far away something is
two eyes for depth
eyes dont occupy the same space so the brain puts both views together because they are slightly different
binocular disparity
image on the left retina is different from that in the right
stereopsis
we can see depth because of binocular disparity
Multimodal
we perceive objects through more than one mode of sense
- mcgurk effect
Mcgurk effect
we hear speech through our years but the seeing how someones mouth moves as they speak also has an effect on how we hear
amplitude
related to loudness
frequency
- cycles per second
- related to pitch
- can hear 20 to 20 000 Hz
decibels (dB)
- ratio scales, can be used to describe any ratio of any value
dB sound pressure level (SPL)
-physical experience
- not the same as loudness (mental experience)
- can hear -10 to 140 dB SPL
dB sound pressure level (SPL)
-physical experience
- not the same as loudness (mental experience)
- can hear -10 to 140 dB SPL
pinna
- funnels sound to ear canal
- top outside part of ear (where cartilage piercing would be)
ear canal
sends sound down
ossicles
- smallest bones
- set of bones called the middle ear
ear drum
vibrates as sound hits it
cochlea
- sensory cells detect sound and send it to auditory nerve
- fluid filled chamber s
- breaks down sound into high and low pitches
apex
part of cochlea that is responsible for low pitches (20Hz)
base
- cochlea part that has high pitches (20000 Hz)
basilar membrane
sensory cells sit on top of it
- it is the straight line down the middle of cochlea
- it vibrates as sound passes through
tectorial membrane motion
- membrane that sits on top of basilar
- moves left to right at the same time as basilar vibrates
hair cells
- detect and transduce mechanical vibrations of membranes
- responsible for transduction in the ear
how it all works together in the ear
up and down motion of basilar work with left to right motion of tectorial create a shearing force with allows hair cells to vibrate and transduce sound into signals that the brain understands
auditory cortex
- temporal lobe
how multimodal perception works
visual brain influences speech processing in the auditory brain areas and multi-sensory areas (posterior superior temporal sulcus)
- hearing and vision interact (explain mcgurk effect)
