Mental Imagery Flashcards
Mental Images
We experience the world via perception – but is there a different way of “perceiving”? Can we create perception in our mind?
There is evidence for mental images – seeing with “the mind’s eye”
One question is whether these images are “real”. The Behaviourists (e.g. Watson) denied their existence as unproven
In support of mental imagery:
The 19th-century chemist Kekule reported that the structure of benzene came to him as a visual image in a dream
The conceptual peg hypothesis
Early cognitive psychologists found that pairs of concrete nouns can be more easily remembered than abstract nouns
E.g. Hotel - Student vs Knowledge - Honour
Concrete nouns create a mental image to “hang onto”
Do mental images and perception share the same mechanisms?
The classical studies from Shepard & Metzler (1971):
tetris-like blocks
Mental rotation experiments ask whether the manipulation of images is similar to the manipulation of real objects
The result of Shepard & Metzler’s study was that we need longer for mental rotation with increasing angle between the objects to rotate
This means, rotation speed follows real-world physical properties of the stimuli
Thus, we might have “real” images in our mind that we rotate (60 degrees / second)
Do mental images and perception share the same mechanisms? Stephen Kosslyn (visual scanning)
Another way to investigate the properties of mental images is visual scanning
In visual scanning experiments, participants first have to scan images and then create a mental image in their mind
Participants were then asked to focus on one part (e.g. the anchor), and then decide whether another part (e.g. the motor) was present or not
Results: Stephen Kosslyn (visual scanning)
He found that it took participants longer to make the decision the further away the crucial part was from the initial starting point (here the anchor)
Thus, he concluded that people created real mental images and travelled along the images in their minds when solving the problem
Results: Stephen Kosslyn (visual scanning) Island Experiment
In a similar experiment Kosslyn asked participants to scan and imagine an island
People then had to mentally travel to various locations on the island
The time it took to respond to questions about these locations increased linearly with the distance on the image, confirming his earlier results
Do mental images and perception share the same mechanisms?
Zenon Pylyshyn (critical of Stephen Kosslyn’s results)
Pylyshyn argued that Kosslyn’s experiments do not show that we have mental images involving spatial representations in our mind
The experience might be spatial, but could just be an epiphenomenon that doesn’t do anything
He argued that the underlying representation would be a propositional representation
E.g.
UNDER
(BALL, TABLE)
Revert back to verbal codes perhaps the representation is is not an image
Pylyshyn (semantic network hypothesis)
According to Pylyshyn, a propositional representation is not depictive (or spatial) but similar to nodes in a semantic network
Travelling within this network between nodes would also explain the longer response times that Kosslyn observed
Spatial representation hypothesis (supports the notion the humans have a mental image)
There is overwhelming evidence for the spatial representation hypothesis
For example, it takes participants longer to answer a question about the mental image of a rabbit when imagined beside an elephant as compared to when imagined beside a fly
The explanation is that the bigger animal fills more space in the mental image
Do mental images and perception share the same mechanisms?
Farah (1985)
Farah (1985) asked participants to imagine a letter (H or T) on a screen
Then she briefly flashed two squares on the screen, one was empty, one contained a letter
Participants had to report what came first: the square with the letter or the empty square?
Participants were better at the task when the letter shown was the same letter as they had imagined before
This study demonstrates that…
You can prime yourself with your metal image
The mental image must be real as it effects how we process later stimuli
Do mental images and perception share the same brain networks?
With the availability of brain imaging techniques, it became possible to ask whether mental imagery and perception rely on similar brain structures
For imagination of music, very similar activation was observed in the auditory cortex compared to listening to music
Similarly, studies repeatedly found that object areas in the brain (in the ventral visual stream) were activated for both perception and visual imagery
FMRI studies
Recently, more sophisticated analysis techniques for functional magnetic resonance imaging (fMRI) became available
These techniques, called “multivoxel pattern analysis” (MVPA) allows to compare how similar the activation patterns in brain regions are for different experimental conditions
Using MVPA, researchers have found that the patterns of activation in ventral visual cortex are so similar for perception and mental images that one could be predicted from the other
Does the manipulation of mental images also rely on brain networks for real manipulation?
How real are mental images? Shepard & Metzler (1971) have argued that people rotate mental images of their cubes in their mind
Does the mental rotation involve motor structures of the brain – although it happens only in the mind?
Some fMRI studies found activation in primary motor cortex during mental rotation – in a region that controls hand movements
However, other did not observe motor cortex activation during mental rotation at all (Sauner et al., Eur J Neurosci, 2006)
Maybe we only need our motor cortex when we imagine using our hands?
Transcranial Magnetic Stimulation (TMS)
to investigate the involvement of the primary motor cortex in cognitive activities
The stimulation of the hand area of primary motor cortex makes the muscle at the respective hand twitch!
The strength of the muscle activity can be measured and is called Motor-Evoked Potential (MEP)
It can be used as an indicator for the excitation of the motor cortex during a cognitive task
When stimulated with TMS during mental rotation, the MEPs are enhanced – indicating that the motor cortex is activated!
This is further evidence that the same brain regions are involved in mental and real rotation, independent of strategies
Do mental images exist?
There is compelling evidence from behavioural and neuroscience studies that mental imagery is very similar to perception
The brain is using the early perceptual regions for the creation of mental images, pointing to a strong overlap (however, not identical activation!)
The manipulation of mental images is very similar to the manipulation of real images, and it also seems to involve brain regions for real manipulation
However, there are also differences: Mental imagery takes effort, is fragile, and there seem to be differences in individual skill/ability
