PSYB57H3 Chapter Notes - Chapter 10: Mental Rotation, Image Scanner, Soltyrei
Chapter 10: Visual Knowledge
•Far more is known about visual knowledge than auditory, olfactory, taste knowledge, etc.
Visual Imagery
•Visual images can have an everyday use—as a basis to make decisions, or as a remembering aid
Introspections About Images
•Within the last century or so, psychologists have begun to gather systematic data about imagery
•Francis Galton asked participants to introspect, and the self-reported data he obtained fit well with
common sense: participants reported that they could “inspect” their images just like a picture, and
viewing them from a certain position and distance, showing that they are picture-like
•However, some of his participants reported richly-detailed images, while other reported very sketchy
images or no images at all. Do people differ in the nature of their imagery?
•Keep in mind a methodological concern raised by Galton’s data: perhaps all participants had the
same imagery sills, but some were cautious about what they say, while others liked to discuss it.
So, what is needed is a more objective approach
Chronometric Studies of Imagery
•For more objective data, participants are asked to do something with their images rather than describe.
Usually they are asked to make a judgement based on the image. The speed of the judgements can be
then be measured
•The pattern of what information is included and prominent depends on the mode of presentation; for
description, the features that are prominent will be distinctive and strongly associated with the object
being described, and for depiction, distinctiveness and association won’t matter—instead, size and
position will determine what’s prominent and what’s not
•Describing a cat would include distinctive features like whiskers, claws, and so on. But not a head
because it is too obvious to mention. Drawing a cat would have a prominent head because it is
larger and up front. Claws and whiskers may be less salient because they are small and so would
not take up too much space in the drawing
•So what information is available in a visual image? Depictive (pictorial) or descriptive (verbal)? Self-
reports indicate picture-like representations. Is this confirmed by the data?
•Thinking about cats via imagery results in quicker responses for picture-like representations (head
faster than claws) and thinking about cats without imagery results in quicker responses for verbal
representations (claws faster than head)
•In an image-scanning procedure, participants were asked to memorize a map and image a black
speck moving from one landmark to another, and hit a button when the speck “reaches” the target. This
allowed for measurement of how long the participants needed to “scan” from one landmark to the next.
Data suggests that participants scan at a constant rate, so doubling the distance between landmarks
doubles the time needed, tripling the distance triples the time, and so on. Similar results appear for
“zooming in” on a mental image
•These results suggest that travel in the imagined world resembles travel in the actual world, at least
with regard to timing
•The images will represent information about all the shapes and sizes within the scene, and it will also
preserve a diverse set of spatial relationships. It’s in this fashion that images directly represent the
geometry of the scene, and it’s in this way that images depict the scene rather than describing it, and so
are more similar to pictures or maps than they are to descriptions
Mental Rotation
•Other results make a similar point with regard to the transformation of mental images
•Mental rotation tasks show that the farther you have to imagine a form rotating, the longer the
evaluation takes
•Participants can imagine in-depth 3D rotations as easily as 2D rotations. Apparently, they can represent
3D forms in their images, and they can imagine these forms moving in depth. Therefore, in
circumstances, visual images are not mental pictures; they are more like mental sculptures
Avoiding Concerns About Demand Character
•Participants in these studies know that moving a longer distance takes more time; perhaps they are
controlling the time of their responses to create a “normal” pattern. Perhaps they are not imagining
rotations or scanning across an image at all, but rather waiting a moment before hitting the button for
longer distances
•One reason they might do this is to give “good data” to be helpful. As a result, they are sensitive to the
demand character of the experiment—cues that might signal how they are “supposed to” behave in
that situation
•Another possibility is that this sort of “simulation” is what imagery really is all about. Perhaps in trying to
“imagine” something, a person draws on his knowledge about how the event would unfold in the real
world and tries to simulate this event in the best way. So, longer times may occur because people know
these manipulations should take more time and so try their best to simulate the process
•We can set these concerns aside, and maintain the claim that the scanning and rotation data are as
they are, not through simulation, but indeed because of how images represent spatial layout. Several
lines of evidence support this claim. In several studies, judgements about spatial layouts are asked to
be made, without mentioning imagery. This should diminish the demand character and avoid suggestion
for simulation of “mental travel.” Even then, participants spontaneously form images and scan across
them, and show longer response times for longer scans
Interactions Between Imagery and Perception
•Forming a visual image interferes with seeing and forming an auditory image interferes with hearing
•Visualizing and perceiving draw on similar mechanisms, so that one of these activities can serve to
prime the other
•The specific brain structures required for vision are crucial for imagery as well, and this can be
documented in several ways, including neuroimaging techniques; the occipital lobe is active in vision
and in visualizing before the “mind’s eye”
•Area V1 and Area V2 are involved in the earlier stages of visual perception, responding to the specific
low-level features of the input. These same areas are particularly active when participants maintain
highly detailed images, and activation increases as larger and larger objects are imagined
•Area MT/MST is highly sensitive to motion in visual perception, and is particularly active when
imagining movement
•Brain areas that are especially active in face perception are highly activated when imagining faces
•Disruption of Area V1 (where axons from the visual system first reach the occipital lobe) with TMS
causes problems in vision as well as visual imagery
•People who lose the ability to perceive a colour, or fine detail also have problems visualizing these
(complications to this to be discussed later)
•Brain damage also causes parallels in how people pay attention to input and imagery; e..g, patients
with neglect syndrome may only pay attention to what’s on the left in visual input and imagery
Sensory Effects in Imagery
•Researchers indicate that imagery and perception function in similar ways; in other words, the research
indicates a functional equivalence between many aspects of visual imagery and perception
•Visual acuity—ability to see fine detail, greater at center of visual field than periphery. Two-point acuity
tests measure the ability to see fine detail. The closer two dots are, the harder it is to see the gap
between them and distinguish as two separate dots rather than one dot. Acuity is greatest when looking
directly at them and far worse if positioned 10 degrees away from the line of vision. To test this in
imagery, the dots are removed and participant is told to imagine that they still present. Participant
moves the eyes further and further from the imagined position and judges if the dots are still separate
•The imagery data, just like perceptional data, fell off abruptly if dots aren’t in the center of vision;
and fell off more rapidly if participants looked above or below the dots rather than to left or right
Document Summary
Chapter 10: visual knowledge: far more is known about visual knowledge than auditory, olfactory, taste knowledge, etc. Visual imagery: visual images can have an everyday use as a basis to make decisions, or as a remembering aid. So, what is needed is a more objective approach. Chronometric studies of imagery: for more objective data, participants are asked to do something with their images rather than describe. Usually they are asked to make a judgement based on the image. But not a head because it is too obvious to mention. Drawing a cat would have a prominent head because it is larger and up front. This allowed for measurement of how long the participants needed to scan from one landmark to the next. Data suggests that participants scan at a constant rate, so doubling the distance between landmarks doubles the time needed, tripling the distance triples the time, and so on.
