Week 8: Visual imagery Flashcards
Mental imagery
ability to mentally recreate perceptual experience in the absence of a sensory stimulus (EX. losing keys and visualise prior path to retrace)
Dual-coding theory
Human knowledge is represented in two separate imagery systems (verbal & non-verbal)
- verbal: abstract, symbolic system (language system)
- Non-verbal: modality-specific system (based on sensory-motor information; image system) > imagining a dog by actually “seeing” a dog in one’s head
Imagery debate facts
- People experience mental images
- There are many ways that imagery influences cognition
Imagery debate question
What format or code does imagery take in our minds? Kosslyn vs Pylyshyn
Kosslyn
images are depictive representations
- More in line with everyday experience
- Preserves spatial and perceptual information
Pylyshyn
images are descriptive representations
- Images as epiphenomenon
- Language: the word “Sid Smith” doesn’t look like the building
- Simpler: encompasses depictive argument too
Epiphenomenon
Computer heats up as you write essay, the longer you work the hotter it gets
But the heat didn’t cause the essay to get written; heat is a by-product of computer processing
Mental Scanning Study (Kosslyn, 1973)
If visual images are analog codes of physical stimuli then it should take more time to travel longer distances and longer to process larger mental distances
how long to look at flower but alt explanation: stored information on flower and running through list in head as opposed to seeing the flower (descriptive)
Mental rotation study (Shepard and Metzler, 1971)
Investigated time it took to rotate mental abstract images. Theory: takes longer to rotate when angular distance is larger. Results showed a linear relationship between the amount of rotation and reaction time in identifying wether shapes were identical
Mental Scaling
How much one can see of an object depends on size and distance from the viewer.
Mental Scaling Study (Kosslyn 1975, 1978)
Cat next to elephant vs cat next to butterfly. Quicker in stating cat has claws when next to butterfly because didn’t have to zoom in as much mentally.
Cat next to elephant-sized butterfly or cat next to butterfly-sized elephant. Took more time to respond to former because of relative size.
Imagery and Perception (Perky, 2010)
Theory: mental images should use similar cognitive processes as pictures in our minds
Create and describe a mental image of a lemon. Matched projection even though they could not perceive it.
Imagery and Perception- Interference: Segal & Fusella (1970)
While imagining either a tree, a note or nothing report what stimulus you here. Results: detection rates for visual stimulus were low when imagining a tree and similarly with harmonica and phone ringing. You are using up resources.
Imagery and Perception- Facilitation: Farah (1985)
Pts shown a faint T or H and had to visual T or H while detecting. Presenting congruent stimuli enhanced detection performance.
Motion Aftereffects
illusory visual effects that occur after prolonged viewing of a stimulus. Happens because cells in visual system. When a viewer looks away the opposite direction of motion is detected.
Winawer et al (2010)
Imagine motion in one direction for 60 seconds> was enough to bias pts perception of a motion, creating motion aftereffects
Reed (1974)
Does rhombus fit into original shape? If mental images were depictive, they should easily be able to indicate if new shapes were part of the original from memory.
Some cases pts were acuarte some not. Explained: giving verbal labels to objects instead of spatial characteristics.
Arguing against depictive representations… experimenter expectancy
(Researchers inadvertently convey the
anticipated results of the experiment
to participants, altering behavior.)
Arguing against depictive representations… demand characteristics
Participants form an interpretation of
the researcher’s purpose and
subconsciously change their behavior.
Pylyshyn critique
Because participant performance in experiments on depictive representation varied depending on task details, Kosslyn’s results only support their theory because that is what participants thought they were supposed to do
Evidence from neuroimaging
there are shared mechanisms between perception and imagery but are not the same. recorded cell activity in the primary visual cortex (V1) and memorised/ answered questions about the lines by visualising 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)
Evidence from neuro: O’Craven & Kanwisher (2000)
Imagery and perception activate the same specialized areas of the brain.
Is activity in the fusiform face area (FFA) and parahippocampal place area (PPA)
similar in imagery vs perceptual tasks? Pts were shown familiar faces and buildings while in an fMRI machine.
Results:
FFA showed greater activity when viewing and imagining faces (vs buildings).
PPA showed greater activity when viewing and imagining buildings (vs faces).
Could determine if someone was viewing a face or building from brain activity.
Evidence from neuro: (Ganis et al., 2004)
Re-examining brain activity in imagery and perception with newer techniques.
Front brain: planning, cog control, attention & memory showed the most similarity to visual perception and imagery tasks
difference between imagery and perception
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.
