Sensation and Perception Flashcards

(80 cards)

1
Q

modalities

A

sensory brain region that process different components of the perceptual world.

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2
Q

define psychophysics

A

scientific method for investigation of relationships between physical stimuli and psychological experience

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3
Q

what is the absolute threshold

A

the minimum stimulus discriminated reliably from no stimulus. need to respond yes 50% of the time for a trial to be successful

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4
Q

what are the 5 senses thresholds

A

on picture

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5
Q

what is the difference threshold / just noticeable difference

A

the minimum difference in stimulus intensity necessary to tell the two apart

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6
Q

what is webers law

A

that the just noticeable difference is a constant proportion despite variations in the stimulus

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7
Q

what is the aim in detection experiments

A

for the ppt to discriminate the presence of a stimulus from background noise

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8
Q

how does a ppt do this

A

adopt a response criterion (= attitude to the decision)

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9
Q

what is signal detection theory

A

an observation that the response to stimulus depends on a persons sensitivity to the stimulus in the presence of noise and on a persons response criterion

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10
Q

Signal detection theory allows us to measure sensitivity and bias separately how?

A

using hits and false alarms.

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11
Q

describe the ways in which a ppts response could be categorised

A

hit = said yes was yes
miss = said no but was there
false alarm = said yes wasnt there
correct rejection = was no said no

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12
Q

what effects response criterion

A

your evaluation of the costs and benefits of the different possible outcomes e.g is there a tumour said no but it is there = death

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13
Q

what is d prime

A

a statistic that gives a relatively pure measure of the observers sensitivity or ability to detect signals

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14
Q

what is sensory adaptation

A

sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions

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15
Q

what is visual acuity

A

ability to see fine detail

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16
Q

what is visible light

A

the portion of the electromagnetic spectrum that can be seen

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17
Q

how we see

A

see picture

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18
Q

describe the retina

A

the surface of the retina is composed of photoreceptor cells the rods and cone beneath a layer of transparent neurons the bipolar and retinal ganglion cells

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19
Q

describe the world on your retina

A

inverted as has passed through the lens
topographic - reflects real world spatial relationships
much of view common to both retina but also sees parts the other doesnt

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20
Q

what happens from the retina to the brain

A

visual signals relay to primary visual cortex (V1) via the lateral geniculate nucleus
prior to this half the optic nerve fibres from either eye cross over at the optic chiasm so Right visual field to left hemisphere

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21
Q

what is a receptive field

A

region of the sensory surface that when stimulated causes a change in firing rate of thay neuron - on centre cells off center cells

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22
Q

receptive field info

A

each photoreceptor receives light from a specific part of the visual field so its receptive field corresponds to a specific part of the visual field

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23
Q

what is the receptive field of the ganglion determined by

A

the positions of the photoreceptors to which it connects

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24
Q

describe the parts of the receptive fields

A

functional and spatial characteristics - most are center surround type. ganglion cell is sensitive to differences between illumination in the centre and surround portions of its receptive field

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25
describe simple cells
larger receptive fields than ganglion cells they respond to edges of a certain orientation in a certain position
26
describe complex cells
combine input from many simple cells with the same orientation turning and adjacent receptive fields. can respond to an edge of a particular orientatopn st any position in their receptive field
27
describe hypercomplex cells
combine input from many complex cells to respond to increasingly refined features
28
bottom up hierarchy of feature detectors see phone
see picture
29
what is motion
a powerful cue for alerting and orientating and for form perception
30
what is space constancy
we factor out self generated movement to perceive only movement arising in the world
31
what are the two possibilities for space constancy
monitoring eye muscle systems for sensory (afferent) or motor (efferent) signals
32
observations linked to space constancy
the world does not stay stable when the eye is moved passively (sensory signal but no motor signal = space constancy fails) the world seems to move when we try to move a paralysed eye (motor signal but no sensory signal = space constancy maintained)
33
what can we conclude from the space constancy observations
the brain automatically factors out from the image motion signal(IMS), the corollary discharge signal (CDS) which is an exact copy of the motor signal sent to the eyes
34
describe evolutionary utility
dont experience the world directly, through the filter of own perceptual system. do not present objective reality, they have evolved to reconstruct reality in a way that is biologically useful
35
how does colour vision help
classify and identify objects | important signalling mechanism in nature. facilitates perceptual organisation of scene into distinct objects
36
what determines the colour
the wavelength of light that it reflects. most objects reflect a mixture of wavelengths
37
what are the two types of photoreceptor
rods and cones
38
describe rod cells
very light sensitive but all contain same photopigment (rhodopsin) they provide low light acuity, light sensitive peripheral vision which is monochromatic
39
describe cone cells
they are tightly packed in the central fovea giving high acuity colour vision. cones come in three varieties depending on the photopigment they contain
40
what are the three absorption spectra of the cone cells
``` blue = S and 419 nm wavelength green = m 531 red = L 559 nm ```
41
how do the cone cells work together to produce images
the combination of responses from the S M and L cones leads to perception of all colours
42
what is colour transduction
trichromatic
43
describe the neural coding of colour
it is an opponent process. the signals from the red green and blue cones are coded as opponent pairs. a retinal ganglion cell may be excited by firing of red cone and inhibited by firing of green
44
describe colour constancy by chromatic adaptation
wavelenghts reflected by object are determined by objects reflectancy + wavelengths in illumination. colour constancy reduces sensitivity to the dominant wavelengths in the light with our current environment. same colour across changes in illumination
45
describe perceptual constancies
means we can see real unchanging properties in the world despite large changes in stimulation
46
what is the problem with vision
recovering a 3d world from a 2d one. no unique solution so do it by piecing together as much info as is available and making assumptions about the world
47
what is the depth cues table on
my phone
48
what is binocular disparity
two eyes have slightly different views. by sensing the disparity between the objects image in the two eyes the brain can calculate depth
49
what is the process of matching up disparate images as seeing in depth called?
stereoscopic vision
50
describe stereoscopic vision
slightly different images to each eye - images compared computed and vivid depth is experienced
51
what is motion parallax
a dynamic monocular retinal depth cue
52
when are static (pictoral) depth cues available
when viewing a static scene such as a picture through even one eye
53
what are the pictorial depth cues
height in scene blur and interposition
54
explain size perspective and texture gradient as a pictorial depth cue`
size - retinal image projected by an object reduces in proportion to distance from the eye perspective - brain assumes parallel edges texture gradient - the braini assumes a constant grain size
55
explain size and distance in more depth
how far away, interpret image size, tells us how big the object is. depth is a cue to object size
56
what is size constancy
tendency to take distance into account when estimating object size. far objects not as small as they should because we size them up
57
how does familiar size relate to depth perception
familiar with real size use it to infer distance
58
what are extra retinal depth cues
do not come from visual image but from movement of the eyes
59
how do extra retinal depth cues work
monitoring the convergence angle of the eyes the brain can calculate the distance to a point of fixation - trigonometry
60
what did the gestalt psychologists propose
the whole is other than the sum of the parts
61
what are the proposed laws of perceptual organisation also called
heuristics
62
how is the problem of vision solved
all of the depth cues and heuristics (assumptions)
63
what are the laws of perceptual organisation | pragnanz to prox
simplicity Law of pragnanz - stimulus patter is seen such that the resulting structure is as simple as possible similarity - similar things group together proximity - near things group together
64
rest of the laws of perceptual organisation
good continuation - points on straight or smooth lines belong together closure - often aided by cues of good continuation we tend to see object as complete despite occlusion. common fate - things that move together belong together meaningfulness/ familiarity - things are more likely to form groups is those are familiar
65
how do heuristics work in the real world
make perception more efficient under normal conditions but mislead us when normal conditions dont apply.
66
what is figure ground segregation
figure is the thing in the scene with ground out uniformly behind it. figure ground border belongs to thing. regions w symmetry tend to be seen as the figure. smaller regions tend to be seen as figure
67
is lower or upper part the figure - what else
lower in 84% of free viewing | meaningful shapes are seen as the figure.
68
how does figure ground segregation link to object reognition
recognition interacts with and influences FGS
69
top down or bottom up
perception doesnt just come from sensory data (bottom up) actively constructed using context knowledge and expectation (bottom down)
70
how do bottom up combine
the predictions about the world (top down) are continuously refined by comparing them to sensory data (bottom up). the predictions and prediction errors are what we experience.
71
how is perceptual inference bayesian
his work on conditional probabilities describes how we should adjust our beliefs according to new evidence. prior prob.(how much we expect something) and sensory data (how much evidence we have for it)
72
what is synaesthesia
person experiences sensations in one modality when a second modality is stimulated
73
what are some characterisctics of synaesthesia
cross modal pairings are stable over time. can show automatic interference or pop out effects. grapheme - colour synaesthete slowed by letters in wrong colour
74
is synaesthesia result of memories of coloured letters and numbers
a learned association between colour and grapheme doesnt explain historical reports. other types of the condition and martian colours
75
are synaesthetes on drugs
LSD - pharmacologically induced may not based on the same neural mechanisms as the congenital synth. not everyone who uses LSD experiences it
76
low and high level
low level only letter not number | high level letter and number
77
costs of synaesthesia
can not be switched off. can be distracting can be intrusive and unpleasant
78
benefits of synaesthesia
can confer mental advantages. richer sensory associations = enhanced memory
79
pruning
synaptic pruning
80
what is the mcgurk effect
if a person sees lip movements of one speech sound while a different is spoken they hear a third sound we use visual info whilst we listen people with hearing loss do this more accurately