10. VISUAL IMAGERY Flashcards
What is visual imagery?
seeing something in the absence of a visual stimulus
What is mental imagery?
- broader term that refers to the ability to recreate the sensory world in the absence of physical stimuli
- people generally have the ability to imagine tastes, smells and tactile experiences
What is the imageless though debate?
- idea of a link between imagery and thinking
- some think that thoughts are impossible without an image
- others contend that thinking can occur without an image
Explain the Paired Associate Learning (Alan Pavio, 1963)
- partis are presented with pairs of words
- eg. boat hat, car house
- during test, they are presented with first word from each pair
- task is to recall the word that was paired with it during the study period
What is the Conceptual Peg Hypothesis and how is it related to Paired Associate Learning?
Conceptual Peg hypo- concrete nouns create images that other words can ‘hang onto’.
- for eg. if presenting the pair of boat hat in the paired associate learning task, then presenting the word boat later will bring back the boat image
- this provides them a number of ‘places’ on which participants can place their hat in their mind
What is Mental Chronometry, an describe and example that can explain it
Mental chronometry- determining the amount of time needed to carry out various cognitive tasks
- partis saw pictures of cuboids and their task is quickly indicate whether the 2 pics were the same or diff
- the time they took to decide that two views were the same, is directly related to how different the angles were between the two views
- this means that partis were mentally rotating one of the views to see if it matched the other one
- IMP: this experi was one of the first to apply quantitative methods to study the imagery
- suggests that imagery and perception may share same mechanisms
Describe Kosslyn’s (1973) Mental Scanning experiment, and what is the significance of it.
Mental Scanning- participants create mental images and scan them in their mind
- asked ppl to memorize a pic of an object (boat)
- asked them to focus on one part of the boat like the anchor
- then asked to look for another part of the boat like the motor
- press ‘true’ button when they found this part of the boat OR ‘false’ if they cannot find
- IMP: kosslyn reasoned that if imagery, like perception, is spatial then it should take longer for participants to find parts that are located further away from the initial point of focus -> they had to scan across the image
- this exactly happened
IMAGERY AND PERCEPTION BOTH UTILISE SPATIAL REPRESENTATIONS OF THE STIMULUS
What were the criticisms against Kosslyn’s mental scanning experiments?
- Glen Lea (1975)
- proposed that as partis scanned, they may have encountered other interesting parts that could have distracted them and hence increased their reaction time
- KOSSLYN REBUTTED: did another experi to scan betw 2 places on a map.
- they were told to imagine an island that contained seven diff locations
- hence they had to mentally scan betw every possible pair of locations
- they got the same results: took longer to scan between greater distances on the image
- THIS PROVES THAT VISUAL IMAGERY IS SPATIAL IN NATURE
- Zenon Pylyshyn (1973)
- proposed the imagery debate
- IB: debate about whether imagery is based on spatial mechanisms, such as those involved in perception or mechanisms related to language (called propositional mechanisms)
Further elaborate on the Imagery debate that was mentioned by Pylyshyn (1973) as criticism towards Kosslyn’s mental scanning experiments.
spatial representation- kosslyn interpreted the results of his research on imagery as supporting the idea that the mechanism responsible for imagery involves spatial repre
Pylyshyn DISAGREED with this, saying that just because we experience imagery as spatial, doesnt mean that the underlying repre is spatial.
- he proposed that mechanisms underlying imagery involves Propositional representations
- PR: repre in which rls can be represented by abstract symbols such as an equation or a statement such as ‘the cat is under the table’.
Describe Kosslyn’s (1978) size in the visual field experiment
The further smth is, it is difficult to see the small details as it only fills a portion of your visual field. As you move closer, it fills more of your visual field and you can perceive details like the door handle more easily.
- asked partis to imagine 2 animals (elephant and rabbit) next to each other
- imagine they were standing close so that the larger animal fit most of visual field
- then asked qns like ‘does the rabbit have whiskers’
- asked them to find the part of the animal in their mental image and ans quickly
- when he repeated this, he told them to imagine a rabbit and fly
- they now created larger images of rabbits
- RESULT: partis answered qns about the rabbit more rapidly when it filled more of their visual field
Mental walk- imagine they were walking towards their mental image of animal
Overflow- when image filled the visual field or when its edges started becoming fuzzy
- he then got them to do mental walk
- task is to estimate how far away they were from the animal when they began to experience overflow
- RESULT: partis had to move closer for small animals than for larger animals
- HENCE THIS PROVIDES FURTHER EVI THAT IMAGES ARE SPATIAL JUST LIKE PERCEPTION
Describe Martha Farah’s H or T experiment
- had partis to imagine letter H or T on screen
- then pressed a button that caused 2 squares to flash, one after another
- one square contained a target letter, which was either a H or T
- task is to indicate whether the letter was in first square or second
- RESULTS: target letters was detected more accurately when partis had been imagining the same letter than the different letter
- HENCE, farah interpreted this results as showing that perception and imagery share mechanisms
What is the relevance of Kosslyn (1995)’s topographic map
- the visual cortex is organized as a topographic map
- specific locations on a visual stimulus cause activity at specific locations in visual cortex
- kosslyn instructed partis to create small, medium and large visual images while they were in a brain scanner
- looking at a small object causes activity at the back of the visual cortex
- larger objects cause activity to spread towards the front of the visual cortex
HENCE, BOTH IMAGERY AND PERCEPTION RESULT IN TOPOGRAPHICALLY ORGANIZED BRAIN ACTIVATION
Explain Ganis et al. (2004)’s experiment to determine if there is an overlap between brain areas activated by perceiving an object and those activated by creating a mental image of them.
- fmri to measure activation
- perception condition: partis observed a drawing of an object
- imagery condition: told to imagine a picture that they had studied before
- both had to answer a question ‘is the object wider than it is tall’?
- RESULTS: activation in 3 different locations in the brain
- A) perception and imagery both activated at same areas in frontal lobe
- B) shows the same result further back in the brain
- C) shows activation in the visual cortex in the occipital lobe at back of brain
- HENCE, THERE IS ALMOST A COMPLETE OVERLAP OF THE ACTIVATION CAUSED BY PERCEPTION AND IMAGERY IN THE FRONT OF THE BRAIN, BUT SOME DIFF IN THE BACK
What is multi voxel pattern analysis (MVPA)
- to train a classifier to associate a pattern of voxel activation with particular stimulus (like eg. apple and pear)
- then to present a stimulus and see if the classifier can identify it based on the pattern of voxel activity created by the stimulus
Describe Kosslyn (1999)’s bar stimuli experiment and its significance
- presented transcranial magnetic stimulation to visual cortex while partis were doing task
- either did perception or imagery task
- perception task- partis briefly viewed a display (of bars) and make judgement about the stripes
- eg. are the stripes in quadrant 3 longer than those in quadrant 2?
- imagery task was the same, just that they closed their eyes and used their own mental image
- reaction time was measured to make the judgement when TMS was applied to the visual area
- RESULTS: show that stimulation caused partis to respond more slowly
- this slowing effect occurred for both perception and imagery
- concluded that BRAIN ACTIVITY IN VISUAL CORTEX PLAYS A CAUSAL ROLE IN PERCEPTION AND IMAGERY
