Imagery Flashcards
What is mental imagery?
- our ability to mentally recreate perceptual experience in the absence of a sensory stimulus
- perception without sensation
- can create mental images of stimuli that you’ve never experienced
What is dual coding theory?
- human knowledge is represented in two separate systems
- non verbal vs verbal
What is the non verbal system?
- modality specific system
- based on sensory motor information
- image system
- images resemble what they stand for
- analog representation
- maintain perceptual features of the stimulus they represent
What is the verbal system?
- symbolic system
- abstract
- language system
- information does not resemble what it stands for
- abstract codes
What is depictive representation?
- non verbal representation
- analog representation
- depictive
- modal
- representations which maintain perceptual features of a stimulus
- like a photo
What is descriptive representation?
- abstract code
- verbal representation
- propositional representation
- descriptive
- amodal (non sensory)
- representations which have no direct connection to the features of a stimulus
- like a computer code
What is the imagery debate?
- we know that people experience mental images and there are many ways that imagery influences cognition
- the debate is what format or code does imagery take in our minds (depictive or descriptive)
Who is Kosslyn?
- argues images are depictive representations
- analog codes that maintain perceptual and spatial characteristics of objects
- preserve perceptual and spatial information
- when you do mental imagery, you’re bringing the representation to mind
Who is Pylyshyn?
- argues images are descriptive representations
- symbolic codes that convey abstract conceptual information, do not resemble the real world
- does not preserve perceptual and spatial information
- images as epiphenomenon: when you do mental imagery you hallucinate images as an effect of accessing the information
- Argues that knowledge is represented propositionally, via the manipulating of cognitive symbols
- Argues propositional codes are the only requirement for thought
- propositions: Can be verified as true or false and Can be used to describe relationships between items
What is an epiphenomenon?
- a mere by product of a process that has no effect on the process itself
Do people process mental images in the same way they process real stimuli?
- If images are depictive (maintain perceptual and spatial characteristics), then people should process images and physical stimuli similarly
- if images descriptive, then mental processing would depend on the number of propositions instead of perceptual & spatial characteristics of stimuli
What is mental scanning?
- Kosslyn
- It should take more time to travel longer physical distances than shorter ones
- It should take longer to process larger mental distances than shorter distances
- Visualize one landmark…scan the
mental image until you have ‘arrived’ at
the target landmark - The time it took to mentally travel
across landmarks increased with the
“distance” - “Distance” between landmarks varied,
but number of propositional properties
between landmarks remained constant - Evidence for depictive representation
What is the evidence for depictive representation?
- mental scanning
- mental rotation
- mental scaling
What is mental rotation?
- Shepard and Metzler
- Investigated the time it took for individuals to rotate mental images of abstract figures
- If mental rotation is similar to the rotation of real objects, then it will take individuals longer to mentally rotate a greater angular distance compared to a smaller angular distance
- Results demonstrated a linear relationship between amount of rotation of one of the shapes and reaction time for participants to identify whether the shapes were the same or different
- Evidence for depictive representation
What is mental scaling?
- Kosslyn
- When things get closer to you, they appear physically bigger until they fill your entire visual field
- Participants imagined animals standing next to an elephant or a fly
- Asked questions about the intermediary animal (e.g., does this cat have claws)
- Participants answered slower when the intermediary animal was paired with the elephant because they needed to mentally “zoom in”
- Then replicated with “elephant-sized fly” and “fly sized elephant”
- Evidence for depictive representation
What is the relationship between imagery and perception?
- Perky
-Segal & Fusella - Farah
- Motion aftereffects (Winawer)
What did Perky find about imagery and perception?
- If imagery is perception without sensation, then it follows that imagery and perception should use similar cognitive mechanisms
- Imagine and describe lemon
- Simultaneously participants were shown a very dim image of the same item
- Participant mental images matched features of the projection
- they reported not consciously perceiving the image
- Evidence that imagery and perception utilize similar cognitive systems
What did Segal & Fusella find about imagery and perception?
- Evidence for shared perception and mental imagery system from interference
- Indicate what stimulus was presented (arrow, music note or nothing) while either imagining a tree or telephone ringing
- Visual and auditory stimuli were presented at a very low intensity, making detection difficult
- Detection rates for the visual stimulus were lower when imagining a tree
- Detection rates for the auditory stimulus were lower when imagining a phone ring
- If imagery uses the same mechanisms as perception, imagining a visual stimulus would ‘use up’ resources, decreasing detection
- Evidence that imagery and perception utilize similar cognitive systems
What did Farah find about imagery and perception?
- Imagery can also facilitate perception
- Participants shown faint T or H
- “Create a visual image of T or H while detecting the projected letter.”
- Presenting congruent stimuli enhanced detection performance
- Evidence that imagery and perception utilize similar cognitive systems
What are motion aftereffects?
- result when sensory stimulation leads to perceptual overcompensation leading to the illusion motion in the opposite direction
- Winawer demonstrated that mental imagery can create similar perceptual illusions
- Participants “imagined motion in a single direction” for 60 seconds
- This suggests that mental imagery activated the same visual processing neurons
What is the evidence against depictive representation?
- Reed
- Experimenter expectancy
- Demand Characteristics
What did Reed find against depictive representation?
- If mental images are depictive, they should easily be able to indicate if new shapes were part of the original from memory
- In some cases, participants were able to accurately determine if shapes were new or part of the original image
- But in other cases, accuracy was quite low
- Results could be explained if participants were giving verbal labels to objects, instead of storing spatial characteristics
What is experimenter expectancy?
- Researchers inadvertently convey the anticipated results of the experiment to participants, altering behaviour
- Experimenter expectations can influence participant responses (Intons-Peterson)
What are demand characteristics?
- Participants form an interpretation of the researcher’s purpose and subconsciously change their behaviour
What is the evidence from patients with brain damage?
- Patient TC
- Patient PB
- Madame D
- Neuroimaging
Who is patient TC?
- Experienced cardiac arrest after a car accident
- Had damage to the occipital & temporal lobes
- Suffered from cortical blindness
- Both the occipital and temporal lobes are important for visual perception
- Unable to distinguish light from
- Lack of head movements and blinking when observing objects in motion
- Loss of conscious vision was associated with loss of mental imagery
- Could not provide visual descriptions of familiar places, tasks or objects
- TC demonstrated deficits in both perception and imagery abilities
Who is patient PB?
- Experienced a stroke
- Had damage to the occipital lobe
- Suffered from cortical blindness
- PB was able to perform visual imagery tasks
Who is Madame D?
- Experienced multiple strokes
- Had damage to occipital & temporal lobes
- Maintain some visual ability, suffered color blindness
- Could copy drawings but was not able to read or recognize objects or faces
- Madame D was able to perform mental imagery tasks
- Lost perception
- If she could not recognize an object at her home, she would visualize it to help her identify items
- Imagery facilitated perception
Two patients sustained a closed-head
injury.
- There are also cases of individuals who lose mental imagery abilities but maintained perceptual abilities.
- Could not produce mental images
- Neither could draw animals or objects from memory
- Tested normally on: visual perception, memory, language
What are the limits to neuropsychology?
- Generalized function loss
- Difficulty with instructions
- Damage to fibers of passage
What is the evidence from neuroimaging?
- Neuroimaging results tend to support shared mechanisms between perception and imagery, although they are not exactly the same
- Kosslyn
- O’Craven & Kanwisher
- Ganis et al
What evidence did Kosslyn find from neuroimaging?
- Recorded cell activity in the primary visual cortex (V1)
- Participants memorized pictures of black and white stripes
- Answered questions about the lines by visualizing the drawings
- Demonstrated that viewing and imagining the stripes both activated V1 (PET), and that disrupting they were less accurate when V1 cells were disrupted (TMS)
- Showed causality
What evidence did O’Craven & Kanwisher find from neuroimaging?
- Imagery and perception activate the same specialized areas of the brain
- Participants were shown famous faces and familiar buildings while in an fMRI machine
- FFA showed greater activity when viewing and imagining faces
- PPA showed greater activity when viewing and imagining buildings
- Could determine if someone was viewing a face or building from brain activity
- Suggests shared areas of perception and imagery
What evidence did Ganis et al find from neuroimaging?
- Re-examining brain activity in imagery and perception with newer techniques
- Perception: higher-level brain areas (PFC) send top-down signals to perceptual processing areas
- Imagery: a re-enacted perceptual experience where the same neurons are activated by frontal brain areas instead of a stimulus
- Brain areas involved in planning, cognitive control, attention, and memory showed the most similarity in visual perception and imagery tasks (front of brain)
- There was limited similarity in in activity in V1 for the same tasks…this makes sense considering no visual stimulus is present during imagery tasks
What do most researchers agree on?
Imagery is a combination of depictive and abstract proposition and arises from similar brain mechanisms as perception