Imagery and Perception: Do They Share the Same Mechanisms? • 275showing the cat and the table that could be represented in a
picture (● Figure 10.5). Representations that are like realistic
pictures that resemble an object, so that part of the represen-
tation correspond to parts of the object, are called depictive
representations.
We can understand the propositional approach better by
returning to the depictive representation of Kosslyn’s boat in
Figure 10.2. ● Figure 10.6 shows how the visual appearance of
this boat can be represented propositionally. The words indicate
parts of the boat, the length of the lines indicate the distances
between the parts, and the words in parentheses indicate the
spatial relations between the parts. A representation such as this
would predict that when starting at the motor, it should take
longer to scan and fi nd the anchor than to fi nd the porthole
because it is necessary to travel across three links to get to the
porthole (dashed line) and four links to get to the anchor (dot-
ted line). This kind of explanation proposes that imagery oper-
ates in a way similar to the semantic networks we described in
Chapter 9 (see page 250).
In addition to suggesting that Kosslyn’s results can be explained in terms of propo-
sitional representations, Pylyshyn also suggested that one reason that scanning time
increases as the distance between two points on an image increases is that participants
are responding to Kosslyn’s tasks based on what they know about what usually hap-
pens when they are looking at a real scene. According to Pylyshyn (2003), “When asked
to imagine something, people ask themselves what it would look like to see it, and they
then simulate as many aspects of this staged event as they can” (p. 113). People know
that in the real world it takes longer to travel longer distances, just as I know it takes
longer to drive to Philadelphia than to Erie, so, Pylyshyn suggests, they simulate this
result in Kosslyn’s experiment. This is called the tacit knowledge explanation because it
states that participants unconsciously use knowledge about the world in making their
judgments.
Although Pylyshyn was in the minority (most researchers accept the spatial rep-
resentation explanation of visual imagery), his criticisms couldn’t be ignored, and
researchers from the “spatial” camp proceeded to gather more evidence. For example,● FIGURE 10.5 Propositional and spatial, or depictive,
representations of “The cat is under the table.”
“The cat is
under the table”
Propositional
representationSpatial, or depictive,
representation● FIGURE 10.6 How the visual appearance of the boat in Figure 10.2 can be represented
propositionally. Paths between motor and porthole (dashed line) and motor and anchor
(dotted line) indicate the number of nodes that would be traversed between these parts of
the boat. (Source: Reprinted from S. M. Kosslyn, “Mental Imagery,” in S. M. Kosslyn & D. N. Osherson, An Invitation
to Cognitive Science, 2nd edition, volume 2: Visual Cognition, pp. 267–296, Fig. 7.6. Copyright © 1995 with permission
from MIT Press.)PROPELLER HANDLEMOTOR(behind) CABIN (behind)(bottom of)(rear of)(top front of)(side of)(attached to)(front of) WINDSHIELD PORTHOLE ANCHORMotor to porthole: 3 links
Motor to anchor: 4 linksREAR DECK FRONT DECKCopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.