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Psych 1 > SENSATION 1 > Flashcards

SENSATION 1 Flashcards

1
Q

What is attention?

A

the ability to preferentially process some parts of a stimulus at the expense of processing other parts of the stimulus

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2
Q

Why is attention needed?

A

You can’t process everything in the visual scene
simultaneously
your perceptual system has a limited capacity
to avoid being overwhelmed

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3
Q

Overt attention

A

looking directly at an object

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4
Q

covert attention

A

looking at one object but attending to another object

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5
Q

What does it mean to fixate an object?

A

the look at it - eye movements between fixations are BALLISTIC (i.e. very fast)
these eye movements are called SACCADES

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6
Q

what are saccades?

A

when your eyes jump from point to point

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7
Q

what are fixations?

A

the rests b/w jumps, where the eyes stay looking directly at one part of the scene

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8
Q

What directs out attention?

A
  1. an initial involuntary process (mediated by attentional capture)
  2. a subsequent voluntary process (guided by your goals & expectations)
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9
Q

What is attentional capture?

A

when you r first presented w a scene, your fixations are captured by salient parts of the scene (this is involuntary)

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10
Q

What captures our attention?

A

contrast
- regions of colour / luminance contrast
- regions of size contrast
- regions of orientation contrast
- regions of motion / flicker contrast

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11
Q

What are the effects of attention?

A
  • attention speeds responses
  • can influence appearance
  • can influence physiological responding

ATTENTION MAKES PERCEPTION MORE VIVID
Attention affects not only how quickly a person can respond to a stimulus but also the appearance of the stimulus.

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12
Q

what did carrasco et al 2004 show?

A

showed that attention can make objects appear to have a higher contrast (cued grating appeared to be higher contrast)

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13
Q

What is the binding problem?

A
  • diff aspects of a stimulus are processed independently, often in separate brain areas
  • e.g. motion is processed by DORSAL stream and form is processed by VENTRAL stream

The issue of how an object’s individual features are combined (i.e. bound) to create a coherent percept is known as the binding problem.
e.g. how can i associate the right object w the right colour?

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14
Q

What is feature integration theory?

A

suggests that the binding problem is solved by attending to only one location at a time - only features associated w that location are processed so only those features are bound together
- avoids binding features from dif objects

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15
Q

what is a prediction of FIT?

A

if attention is inhibited, features from dif objects will be incorrectly bound together

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16
Q

What did Treisman & Schmidt (1982) find

A
  • showed that illusory conjunctions occur
  • they presented character strings very briefly followed by noise mask
  • the primary task was to report the 2 numbers
  • then O’s were asked to report coloured letters
  • O’s often associated the wrong colour with the wrong letter
  • such incorrect bindings are called illusory conjunctions
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17
Q

Balint’s syndrome

A
  • parietal lobe damage leads to condition here you cannot focus attention on a single object - very prone to illusory conjunctions due to inability to focus attention on a single object
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18
Q

What is a conjunction search?

A

when the target differs from the distractors only by its particular conjunction of features
- some forms of visual search require binding to occur

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19
Q

What does FIT predict about conjunction searches?

A

predicts that attention needs to be applied to each object in turn (one at a time) to determine whether or not the attended object is the target - VERY SLOW

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20
Q

What is a feature search?

A

the target contains a feature (e.g. red) that the distractors DO NOT contain

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21
Q

what does FIT predict about feature searches?

A

predicts that because binding does not need to occur, attention does not need to be applied to each item in turn - FAST

22
Q

What is change blindness?

A

You can only remember a few parts of a scene at one time
If one of those parts change, you notice the change
If some other part of the scene changes, chances are you won’t notice the change

23
Q

Why doesn’t change blindness occur all the time?

A

because changes usually generate motion transients that draw attention to the location change, thereby making it easy to spot the change

24
Q

What are motion transients?

A

 In the previous demonstration, a blank screen was
inserted between images.
 This meant that when the second image was shown,
motion transients occurred for every part of the image -
not just the parts that changed.
 This meant that motion transients did not guide attention
to the change

25
Q

what do state of the art computer object recognition systems use?

A

use artificial neural networks. Athalye et al. (2018) investigated what sort of images
these object recognition systems would misclassify

26
Q

what makes object perception hard?

A
  • the stimulus on the retina is ambiguous
  • objects can be hidden or blurred
  • objects look diff from diff viewpoints & in diff poses
27
Q

why can 2D retinal images be ambiguous?

A

multiple stimuli can give rise to the same 2D retinal image

28
Q

how do humans solve these perception problems & successfully perceive objects & scenes?

A

structuralism vs gestaltism (2 dif schools of thought)

29
Q

Structuralism

A
  • proposed by Edward Titchener
  • distinguishes b/w sensation + perception
  • sensations: elementary processes occur in response to stimulation
  • perceptions: conscious awareness of objects & scenes
  • believe that sensations combine to form perceptions - perception contains NOTHING that was not already present in these elementary sensations
30
Q

Gestaltism

A
  • claim that conscious awareness is more than the sum of the elementary sensations
  • 2 evidences: APPARENT MOTION & ILLUSORY CONTOURS
31
Q

Apparent motion

A
  • observer sees 2 stationary dots flashed in succession
  • although each dot is stationary, we observe MOTION
  • The conscious percept of motion was constructed and was not present in the elementary sensations.
32
Q

illusory contours

A
  • seen in locations where there are no physical contours
  • The conscious awareness of the illusory contour is constructed – there is no physical contour at these locations.
33
Q

According to gestaltism, how can humans perceive objects or scenes?

A

due to perceptual organisation –> bc they can perceptually organize it into its constituent objects

34
Q

How is perceptual organisation achieved?

A

by grouping & segregation

35
Q

what is grouping?

A

the process by which parts of an image are perceptually bound together to form a perceptual WHOLE

36
Q

what is segregation?

A

the process by which parts of a scene are perceptually separated to form separate wholes

37
Q

What is grouping governed by?

A

5 principles
- good continuation
- pragnanz
- similarity
- proximity
- close fate

(2 extras: common region, uniform connectedness)

38
Q

What is good continuation?

A

principle of grouping
- Aligned (or nearly aligned) contours are grouped together to form a single object.
e.g. 2 wires on top of each other

39
Q

pragnanz

A

principle of grouping
grouping occur to make the resultant figure as simple as possible
e.g. that panda symbol

40
Q

similarity

A

principles of grouping
- more similar objects there are, the more likely they will be grouped together

41
Q

proximity

A

principles of grouping
- the closer the dots are, the more likely they are to be grouped together

42
Q

common fate

A

principles of grouping
things that are moving in the same way are grouped together

43
Q

common region

A

principles of grouping
elements that are within the same region of space tend to get grouped together

44
Q

uniform connectedness

A

principles of grouping
- connected regions with the same visual characteristics (e.g. colour) tend to get grouped together

45
Q

much of perceptual SEGREGATION has focused on?

A

figure-ground segregation

46
Q

figural properties - regions of image more likely to be seen if:

A
  • they are in front of the rest of the image (Rubin vase)
  • they are at the bottom of the image (but there is no LEFT-RIGHT bias!!)
  • they are convex (Peterson & Salvagio showed that if u see a single border, there is a slight tendency to perceive the convex region as figure)
  • they are recognizable (past experience)
47
Q

What is gist perception

A

getting an overall impression of what the scene is about

48
Q

What did Potter (1976) investigate in relation to gist perception?

A

 In each trial, the observer was cued with a
particular scene description.
 Then she saw 16 randomly chosen scenes,
each for 250 ms.
 Then she was asked if any of the scenes fitted
the description.
 Observers were at near 100% accuracy.
 This showed that observers can rapidly perceive a scene’s gist

49
Q

Fei-Fei and gist perception

A

investigated what the minimum scene
exposure time is needed to perceive a scene’s
gist.
reported that the longer the stimulus
presentation time, the more detailed and
accurate the description

50
Q

how long do you need to extract some gist?

A

27 ms is enough time to extract some gist, and
very accurate perception can be achieved in just
250 ms

Psych 1 (12 decks)

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