Chapter 10: Visual imagery
Visual imagery: seeing an object or scene in the absence of a visual stimulus.
Mental imagery: the ability to recreate the sensory world in the absence of physical stimuli, also
occurs in senses other than vision. Imagery provides a way of thinking that adds another dimension
to the verbal techniques that are usually associated with thinking.
Imagery in the history of psychology
Early ideas about imagery
Imageless thought debate: the idea of a link between imagery and thinking -> thought is impossible
without an image vs thinking can occur without images. Behaviourists finally ended the debate by
saying that the study of imagery is unproductive because visual images are invisible to everyone
except the person experiencing them.
Imagery and the cognitive revolution
Conceptual peg hypothesis: concrete nouns create images that other words can hang onto,
therefore memory for pairs of concrete nouns was much better than memory for pairs of abstract
nouns.
Mental chronometry: an approach to measuring memory by measuring the amount of time needed
to carry out various cognitive tasks. -> time in the mental rotation task. -> imagery and perception
may share the same mechanisms.
Imagery and perception: do they share the same mechanics?
Mental scanning: a task in which participants are asked to create mental images and then to scan
them in their minds.
Kosslyn asked participants to memorize a picture of an object and then to create an image of tat
object in their mind and to focus on one part of it. Then were asked to look for another part of the
object and to press the “true” button when they found this other part and the “false” button when
they could not find it. -> visual memory is spatial, it would take longer to find a part of the object
that was located further from the original focus.
Similar studies: with places on map, with places on island.
Imagery debate: a debate about whether imagery is based on spatial mechanisms, such as those
involved in perception, or on mechanisms related to language, called propositional mechanisms.
Imagery debate: is imagery spatial or propositional
Spatial representation: a representation in which different parts of an image can be described as
corresponding to specific locations in space.
Epiphenomenon: something that accompanies the real mechanism but is not actually part of the
mechanism itself. It is a critique on spatial representation, saying that just because you experience
imagery as spatial, doesn’t mean that the representation is spatial itself. Spatiality is not a part of the
representation, but just something that we experience.
Propositional representation: relationships that can be
represented by abstract symbols
Depictive representation: representations that are like
realistic pictures of an object.
,Tacit knowledge explanation: explanation for the results in the spatial representation experiments
that said that believed that participants simulated the results in those experiments since they knew
that travel times between places took longer etc.
Experiment where participants were shown a screen with a couple of dots, and then afterwards one
arrow, pointing in a direction. The task of the participants was to determine whether the arrow was
pointing at a previously presented dot. Whenever the dot was farther from the arrow, the
participants took longer to respond. -> this experiment is a criticism on the tacit knowledge
explanation because they most likely used spatial representation.
Behavioural experiments: comparing imagery and perception
There is a relationship between the distance of an object and the amount of details one can discern.
Experiment in which participants were asked to imagine an elephant and rabbit standing next to
each other and standing close enough so both of them would take up their whole visual field. Then
asked them whether the rabbit had whiskers. He repeated the experiment by imagining a rabbit next
to a fly. When the rabbit was more filled within the visual field, participants responded more rapidly
to the question. -> imagery is spatial
Mental walk task: task in which participants are asked to imagine walking towards an object. The
task was to estimate how far away from the animal before they began to experience overflow: when
the image filled the visual field or when the edges started to become fuzzy. Participants had to move
way closer for small animals, than for larger animals. -> imagery is spatial
An experiment that measures the effect of variations in one basic visual characteristic in both
perception and imagery. If perception and imagery rely on overlapping representations, then
reaction times should be affected in a similar way for real and imagined stimuli.
Participants in the imagery task were asked to imagine a stimuli shown at the beginning of the test
and imagine the change appearing in the stimuli when the tone sounded and to react as soon as the
imagined change took place.
They did this for lamination, contrast, gratings of different spatial frequency, speed of motion, and
orientation.
Then participants in the perceptual task were asked to do the same, but were actually presented
with a change in stimulus.
The reaction time for perception and imagery looked very similar. And also the bigger the change,
the faster the reaction time in both situations.
The reaction time for the perception task was slightly slower each time, showing that it was
apparently a more difficult task.
If imagery affects perception, and perception affects imagery, then they both have access to the
same mechanisms.
Experiment in which participants were asked to look at a wall and project an image of an object on
them. However, the experimenter was projecting a very dim version of the asked object on the wall.
Participants description of their image matched the projection of the image on the screen
eventhough they reported not having seen an image. Participants mistook the actual picture for
their own mental image.
Other variations of this experiment:
Participants were seated in front of a wall and asked to imagine an H. Afterwards they pushed a
button and two squares were flashed, one of them containing a letter: an H (target) or a T (non
target). If the participants had been imagining an H before, they detected the H more accurately
than the T.
, Imagery and the brain
Studies done with brain imagining techniques like fMRI have shown evidence of perception and
imagery to be closely connected.
Imagery neurons in the brain
Single neurons respond to some objects, but not to others. The same neuron would also respond to
the same imagined objects, but not to other imagined objects. -> imagery neurons.
fMRI
The visual cortex was activated both by perception and imagery. The visual cortex also reacted to
questions like “is the green of grass darker than the green of pine trees” and “is electrical current
measured in amperes?” -> when we visualise something.
Specific visual stimuli can activate specific visual locations in the visual cortex. Small objects activate
the far back of the visual cortex and larger objects spread to a bigger area around this. When asked
to imagine small or large objects, the same effect was measured within the visual cortex. -> study
was not able to be replicated though.
They found out which conditions had to be met in order to find evidence for activation of the
topographically organized visual areas as a result of visual imagery.
1. The task has to require high resolution images of the details of shape.
2. The task should not require spatial images
3. A sensitive fMRI technique needs to be used.
There are overlapping brain areas that are activated by perception and imagery, but there are also
differences.
An experiment with two conditions.
One is a perception condition in which participants are shown a faint drawing of an object that they
had studied before. For the imagined condition participants are asked to imagine an object that they
had studied before. For both of the tasks the participants needed to answer the question: “is the
object wider than it is tall?” Both conditions activated the same areas in the frontal lobe, but the
perception condition also activated the occipital lobe more than imagery. -> visual areas are less
involved in imagery than in perception.
Another experiment only looked at fMRI results and determined whether the participant was
imagining or perceiving in a scenario. They found that activity in the primary visual cortex in the
occipital lobe was a predictor for perception (these respond to more orientationally like lines),
whereas activity in higher visual areas was a predictor for imagery (react more to whole images).
Imaginary also deactivates areas associated with non-visual processing like hearing and touch. A
similar drop was not measured in perception.
Transcranial magnetic stimulation
Showing that an area of the brain is activated by imagery does not prove that this activity causes
imagery. -> brain imagery can also be seen as an epiphenomenon.
Experiment where participants were shown quadrants with stripes and were asked questions
comparing the different quadrants with stripes to each other. This was also done in an imagery
condition, where they were closing their eyes and imagining the quadrants. By using TMS on the
visual cortex, they found that answers slowed down both for perception and imagery -> not an
epiphenomenon.
