74 • CHAPTER 3 Perception
These results for D.F. demonstrate a single dissociation, which indi-
cates that judging orientation and coordinating vision and action
involve different mechanisms. To show that these two functions are not
only served by different mechanisms but are also independent of one
another, we have to demonstrate a double dissociation. As we saw in
the example of Alice and Bert, this involves fi nding a person whose
symptoms are the opposite of D.F.’s, and such people do, in fact, exist.
These people can judge visual orientation, but they can’t accomplish
the task that combines vision and action. As we would expect, whereas
D.F.’s temporal lobe is damaged, these other people have damage to
their parietal lobe.
Based on these results, Milner and Goodale suggested that the path-
way from the visual cortex to the temporal lobe (which was damaged
in D.F.’s brain) be called the perception pathway and the pathway from
the visual cortex to the parietal lobe (which was intact in D.F.’s brain) be
called the action pathway. The perception pathway corresponds to the
what pathway we described in conjunction with the monkey experiments,
and the action pathway corresponds to the where pathway. Thus, some
researchers refer to what and where pathways and some to perception
and action pathways. But whatever the terminology, this research demon-
strates that perception and action are processed in two separate pathways
in the brain.PICKING UP A COFFEE CUP
AND OTHER BEHAVIORS
With our knowledge that perception and action involve two separate mechanisms, we
can add physiological notations to our description of picking up the coffee cup, as
follows:The fi rst step in the process of picking up the cup is to identify the coffee cup among the
vase of fl owers and the glass of orange juice on the table (perception pathway). Once the
coffee cup is perceived, we reach for the cup (action pathway), taking into account its
location on the table. As we reach, avoiding the fl owers and orange juice, we position
our fi ngers to grasp the cup (action pathway), taking into account our perception of the
cup’s handle (perception pathway), and we lift the cup with just the right amount of force
(action pathway), taking into account our estimate of how heavy it is based on our per-
ception of the fullness of the cup (perception pathway).Thus, even a simple action like picking up a coffee cup involves a number of areas
of the brain, which coordinate their activity to create perceptions and behaviors. A
similar coordination between different areas of the brain also occurs for the sense
of hearing. Thus, hearing someone call your name and then turning to see who it is
activates two separate pathways in the auditory system—one that enables you to
hear and identify the sound (the auditory what pathway) and another that helps you
locate where the sound is coming from (the auditory where pathway) (Lomber &
Malhotra, 2008).
The discovery of different pathways for perceiving, determining location, and tak-
ing action illustrates how studying the physiology of perception has helped broaden
our conception far beyond the old “sitting in the chair” approach. These physio-
logical fi ndings, combined with behavioral experiments that have focused on active
aspects of perception (Gibson, 1979), mean that we can call perception “dynamic”
not only because it involves processes such as inference and taking knowledge into
account, but also because of how closely perception is linked to action. In the next
section we show how this idea has been carried even further, by describing neurons
that fi re not only when a person takes action, but also when a person watches some-
one else take action.● FIGURE 3.38 (a) D.F.’s “mailing” task; (b) results
for the mailing task.(a) Task: “Mail” card in slotDF Control
(b) Results of active mailingCopyright 2011 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.