PSYC10003 Lecture Notes - Lecture 33: Mental Rotation, Benzene, Underlying Representation
12 Jun 2018
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Lecture 33, Tuesday, 24 May 2016
PSYC10003 - MIND, BRAIN & BEHAVIOUR 1
LECTURE 33
MENTAL IMAGERY
•Mental imagery;
•Do we have mental images and are they similar to perception?
•Mental rotation;
•Shepard & Metzler and rotating stuff in our mind
•Mental scanning;
•How long does it take to travel through a mental landscape?
•Mental imagery and the brain;
•What happens in the brain when it only rotates in the brain?
MENTAL IMAGES
•We experience the world via perception – but is there a different way of “perceiving”? Can we
create perception in our mind?
•The 19th-century chemist Kekule reported that the structure of benzene came to him as a visual
image in a dream.
•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.
•However, early cognitive psychologists found that pairs of concrete nouns can be more easily
remembered than abstract nouns.
•This led to the conceptual-peg hypothesis: Concrete nouns create a mental image to “hang onto”
•HOTEL – STUDENT, KNOWLEDGE – HONOUR
DO MENTAL IMAGES & PERCEPTION SHARE THE SAME MECHANISMS?
•Mental rotation experiments ask whether the manipulation of images is similar to the
manipulation of real objects.
→ Shepard & Metzler (1971)
•The classical studies from Shepard & Metzler (1971):
•a) How long does it take to rotate images in the mind?
•b) Do we manipulate “images” in our mind, as we would manipulate 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 (with 60 degrees/second)
Lecture 33, Tuesday, 24 May 2016
PSYC10003 - MIND, BRAIN & BEHAVIOUR 1
→ Stephen Kosslyn
•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 (Eg. the anchor), and then
decide whether another part (Eg. the motor) was present or not.
•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.
•In a similar experiment Kosslyn asked participants to scan and imagine an
island.
•People then had to 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.
→ Zenon Pylyshyn
•Pylyshyn argued that Kosslyn’s experiments do not show that we have
mental images involving spatial representations in our mind.
•He said the experience might be spatial, but it also could just be an
epiphenomenon that doesn’t do anything.
•He argued that the underlying representation would be a propositional
representation.
•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.
•However, there is still 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.
