Visual images

1
Visual images

• Recall Baddeleys model
• visuo-spatial sketchpad, phonological loop,
  central executive system
• early work by Paivio showed that one of the best
  predictors of memory performance was how readily
  the word was reported to be imaged

2
Visual images

• How is visual information represented?
• Analogue versus digital debate
• mode of representation is continuous
• mode of representation is propositional
• Shepard Metzler (1971) p. 197 Reed
• presented a pair of 2-dimensional representations
  of 3-dimensional objects
• task judge whether objects were identical or not

3
Visual images

• Shepard Metzler (1971) p. 197 Reed
• Results the mean RT increased linearly with the
  degree of angular rotation between the pair of
  objects
• suggests that participants mentally rotated one
  shape until it was at the same angle as the other
• Kosslyn
• performed a series of studies in which subjects
  were presented a series of pictures. Picture was
  removed, and then subjects were required to make
  judgements about it

4
Visual images

• Kosslyn (contd)
• Results RT was a function of distance between
  components of image (e.g., bow of boat vs rudder
  takes longer than bow of boat vs porthole
• geographical (landmarks) show a similar effect
  e.g., distance between parts of campus
• scaling effect
• imagine rabbit beside elephant rabbit beside
  mouse
• then answer question about rabbits eye
• Results faster RT with mouse than elephant

5
Visual images

• Is imaging like seeing?
• Kosslyn and Shepard propose that these results
  support that hypothesis
• problems with data
• demand characteristics Pylyshyn argues that
  people are simulating operation of perceptual
  system
• e.g., Intons-Peterson Roskos-Ewoldsen (1988)
• imagine you are walking with cannonball vs
  balloon RT cannonball gt RT balloon

6
Visual images

• Brooks (1967) demonstration
• I am going to show you a 4 x 4 matrix, denoting
  one of the squares as a starting square
• I am then going to say aloud a number of
  sentences one at a time. I want you to try and
  remember these sentences as well as you can
  because I am going to test your memory for this
  material

7
Brooks (1967)
8
Brooks (1967)

• in the starting square put a 1
• in the next square to the right put a 2
• in the next square up put a 3
• in the next square to the right put a 4
• in the next square down put a 5
• in the next square down put a 6
• in the next square to the left put a 7
• in the next square down put an 8
• in the next square to the left put a 9
• in the next square to the left put a 10

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Brooks (1967)

• Recall as many of the sentences as you can

10
Brooks (1967)
11
Brooks 1967

• In the starting square put a 1
• in the next square to the slow put a 2
• in the next square to the good put a 3
• in the next square to the good put a 4
• in the next square to the slow put a 5
• in the next square to the bad put a 6
• in the next square to the slow put a 7
• in the next square to the bad put a 8
• in the next square to the quick put a 9
• in the next square to the bad put a 10

12
Brooks 1967

• Recall as many sentences as you can

13
Brooks 1967

• Score data
• spatial

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Brooks (1967)

• in the starting square put a 1
• in the next square to the right put a 2
• in the next square up put a 3
• in the next square to the right put a 4
• in the next square down put a 5
• in the next square down put a 6
• in the next square to the left put a 7
• in the next square down put an 8
• in the next square to the left put a 9
• in the next square to the left put a 10

15
Brooks 1967

• Score data
• nonsense

16
Brooks 1967

• In the starting square put a 1
• in the next square to the slow put a 2
• in the next square to the good put a 3
• in the next square to the good put a 4
• in the next square to the slow put a 5
• in the next square to the bad put a 6
• in the next square to the slow put a 7
• in the next square to the bad put a 8
• in the next square to the quick put a 9
• in the next square to the bad put a 10

17
Brooks 1967

• Results
• recall in spatial condition about 8 instructions
• recall in the verbal condition about 6
  instructions
• Brooks also compared the effects of presenting
  instructions in auditory or visual format
• auditory was better for spatial instructions
• visual was better for verbal instructions
• argued that visual instructions require
  visuo-spatial processing, and thereby interfere
  with performance in spatial condition

18
Divided attention

• Baddeley, Grant, Wight, Thomson, 1975
• subjects performed the verbal and spatial tasks
  of Brooks alone or in combination with a pursuit
  rotor task
• pursuit rotor task keep stylus in contact with a
  spot of light that follows a circular path
• hypothesis performing two tasks at the same time
  should be more interfering if they require
  visuo-spatial cognitive processes

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Divided attention
20
Divided attention spatial processing

• Conclusion
• concurrent spatial tasks interfere with visual
  imagery performance

21
Is imagery spatial or visual

• Hypothesis is imagery spatial or visual
• Design
• divided attention task
• primary task Brooks matrix task (spatial,
  verbal)
• secondary task
• visual--judge brightness of slides
• auditory tracking of pendulum with sound source
  attached to pendulum with flashlight while
  blindfolded sound changes when illuminated

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Is imagery spatial or visual

• Results
• spatial matrix more disrupted by spatial task
  (pendulum task)
• verbal matrix more disrupted by brightness
  judgement
• Conclusion
• spatial matrix task more strongly affected by
  spatial secondary task.
• Suggests that spatial processes are more
  important in imagery task than are visual
  processes

23
Other evidence that visual imagery is not visual

• Blind subjects show many of the effects that have
  been reviewed here
• blind can effectively use visual imagery
  mnemonics
• blind show visual scanning types of effects such
  as Kosslyn has demonstrated

24
Visual imagery and verbal learning

• Baddeley (1975)
• effects of pursuit tracking on performance of
  imageable (bullet - grey) and abstract (gratitude
  - infinite) word pairs
• Background
• imageable word pairs are better recalled than
  abstract word pairs
• dual code hypothesis of Paivio (imageable words
  activate verbal and visual code)

25
Visual imagery and verbal learning

• Baddeley (1975)
• presented lists of pairs of imageable or abstract
  word pairs while performing pursuit rotor task
• at test given first word and had to recall second
  word
• Results
• imageable words better recalled than abstract
  words
• tracking impaired recall of both types of pairs
  equally

26
Visual imagery and verbal learning

• Interpretation
• perhaps pursuit rotor did not interfere with task
  because there was not a strong spatial component
  to the task
• effects of pursuit rotor on words studied using
  the method of loci (Baddeley Lieberman, 1980)
• participants learned list using (method of loci,
  rote learning) either alone or while performing
  pursuit rotor

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Baddeley Lieberman (1980)
28
Baddeley Lieberman (1980)

• Conclusions
• performing a spatial secondary task (tracking)
  interferes with a memory task that has a strong
  spatial component (method of loci)
• Question
• is the visuo-spatial sketchpad is primarily
  spatial in nature, or
• is this result attributable to the spatial
  aspect of the tracking task

29
Logie (1986)

• Purpose
• can non-spatial secondary tasks can disrupt
  (non-spatial) primary tasks
• tasks
• primary task learn word lists using visual
  imagery or verbal rehearsal
• secondary task none or sit facing a screen on
  which coloured patches were shown
• no response required (unattended colour)

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Logie (1986)
31
Logie (1986)

• Purpose
• can non-spatial secondary tasks can disrupt
  (non-spatial) primary tasks
• Method
• primary tasks remember words using rote
  rehearsal or visual imagery mnemonic
• secondary tasks irrelevant speech or line
  drawings (irrelevant pictures)

32
Logie (1986)
33
Logie (1986)

• Conclusion
• non-spatial secondary tasks can interfere with
  memory using imagery procedures
• verbal secondary tasks can interfere with memory
  based on verbal rehearsal procedures

34
Characteristics of visuo-spatial sketchpad

• Information into the sketchpad can be fed by
  visual perception and by generation of a visual
  image (recall imagery expts)
• access to sketchpad by visual information is
  obligatory (recall effects of unattended
  pictures)
• system appears to represent both visual and
  spatial aspects of stimuli
• neuroscience results suggest that separate
  systems encode what and where (Ungerleider
  Mishkin, 1982)

35
Neuropsychology of visual imagery

• Regional blood flow study (Roland Friberg,
  1985)
• subjects were asked to imagine a walk through a
  familiar location and to take alternate left and
  right turns
• measurement of regional blood flow showed massive
  increases in the occipital lobes and in the
  posterior superior and posterior inferior
  temporal lobes
• these are the same regions that show high levels
  of blood flow during visual processing

36
Neuropsychology of visual imagery

• Is there evidence to support dissociations of
  different aspects of visual processing?
• What versus colour
• De Renzi Spinnler (1967) report patients who
  have are colour blindness as a result of cortical
  damage, and are unable to image the colour of
  objects (e.g., what colour is a banana?)
• Beauvois Saillant (1985) reported a patient who
  could draw objects from memory, but could not
  report their colour

37
Neuropsychology of visual imagery

• Is there evidence to support dissociations of
  different aspects of visual processing?
• What versus where Ungerleider Mishkin (1982)
• What nonmatching to sample task
• monkey sees object beneath object is peanut
  (sample) next trial monkey sees two objects, the
  original and a new one
• peanut is beneath new object

38
Neuropsychology of visual imagery

• What versus where Ungerleider Mishkin (1982)
• Where landmark task
• monkey sees 2 trapdoors under 1 trapdoor is a
  peanut
• there is a landmark (a cylinder) closer to the
  trapdoor containing the reward

39
Neuropsychology of visual imagery

• Ungerleider Mishkin (1982)
• trained monkeys to perform each task
• group 1 had temporal lobes lesioned
• group 2 had parietal lobes lesioned
• group 1 fine on landmark task, but impaired on
  nonmatching to sample task
• group 2 showed opposite pattern
• Interpretation
• there are two separate streams of processing in
  the visual system what and where

40
Neuropsychology of visual imagery

• Ungerleider Mishkin (1982)
• puzzle how can you identify an object (what)
  without know about the location of its parts
  (where)
• Goodale Milner (1992)
• What/how hypothesis
• argue that the spatial information is present in
  both streams
• critical difference is the function of the
  spatial information

41
Neuropsychology of visual imagery

• Goodale Milner (1992)
• What/how hypothesis
• argue that the spatial information is present in
  both streams
• critical difference is the function of the
  spatial information
• in the what stream the spatial information
  identifies objects and is associated with
  consciousness
• the end product is a conscious awareness of
  objects, their colour etc.

42
Neuropsychology of visual imagery

• Goodale Milner (1992)
• What/how hypothesis
• the critical function of the how stream is to
  help organisms move
• it knows the location of objects so that you can
  reach to the right spot it knows the shape of
  objects so that you can grasp the object
  effectively
• this knowledge, however, is unconscious

43
Neuropsychology of visual imagery

• Results from patients with lesions supports the
  idea that there are dissociations between what
  and where/how, as does data from cognitively
  unimpaired individuals
• e.g., the visual system is fooled by visual
  illusions, but the grasping system is not
• present visual illusion to individual and have
  them judge size by indicating it using thumb and
  index finger or to pick up the poker chip