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Lecture

PSYC 2650 Lecture Notes - Sundae, Roger Shepard, Fudge


Department
Psychology
Course Code
PSYC 2650
Professor
Dan Meegan

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Visual imagery serves an important role in our daily lives, even without our realizing it. It
plays a causal role in our behaviors, such as when we salivate or feel hungry after
mentally picturing a hot fudge ice cream sundae. While purchasing a new sweater, we
may image how it would look with our black striped pants. Or if buying new curtains for
an apartment, you might mentally rotate each room and scan the number of windows
that need curtains. Although using visual imagery, and operating on those images
through scanning and rotation might seem like an ordinary and automatic act, pulling up
an image (e.g., of your new apartment) from memory and manipulating that image is a
high-level cognitive skill. The way people form and process mental images has been of
interest to researchers in cognitive psychology for many years. At its heart, the mental
imagery debate is about the nature of the mental representations that we use, and their
functional role in cognition.
In the Mental rotation, 2-D ZAP you found that there is a strong relation between the
degree of mental rotation of two-dimensional letters and the time it takes to make
judgments about the letters. This relationship is analogous to longer reaction times to
physically rotate an object. The same relationship between degree of rotation and
response time was found using three-dimensional stimuli. In the 1970s, Roger Shepard
and Metzler presented subjects with pairs of 3-D block figures at various degrees of
rotation from each other. The subjects were asked to judge whether the two figures were
the same (albeit rotated), or mirror images of each other. This ZAP is a replication of
Shepard and Metzler’s original experiment on the mental rotation of 3-D stimuli.]
Your data should have shown that response times to the 3-dimensional stimuli were
proportionately related to the degree of rotation between the two images. The
further the images were rotated relative to each other, the longer it takes to
mentally align them. Shepard's research has shown that the mean speed with which
people rotate images is about 60 degrees a second.
You may have thought that this 3-dimensional rotation task seemed more difficult
than the 2-dimensional version of this experiment. In general, people make more
mistakes in the three-dimensional task than the two-dimensional task, and also have
a longer average time for rotating. However, both the 2- and the 3-dimensional
mental rotation tasks show the same linear reaction between degree of rotation and
response time (though the 3-dimensional graph is steeper).
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