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bird’s color, form, movement, and distance. One of the grand ideas of today’s cognitive neu-
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AP Exam Tip
roscience is that much of our brain work occurs off stage, out of sight. Thinking, knowing,
remembering, and communicating all operate on two independent levels — a conscious,
Dual processing is another one of deliberate “high road” and an unconscious, automatic “low road.” The high road is reflec-
those big ideas that shows up in
several units. Pay attention for the tive, the low road intuitive — together creating what researchers call dual processing
®
AP exam! (Kahneman, 2011; Pennycook et al., 2018). We know more than we know we know.
If you are a driver, consider how you move into the right lane. Drivers know this uncon-
sciously but cannot accurately explain it (Eagleman, 2011). Most say they would bank to
the right, then straighten out — a procedure that would actually steer them off the road. In
reality, an experienced driver, after moving right, automatically reverses the steering wheel
just as far to the left of center, only then returning to center. The lesson: The human brain is
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
a device for converting conscious into unconscious knowledge.
Or consider this story, which illustrates how science can be stranger than science fiction.
During my sojourns at Scotland’s University of St Andrews, I [DM] came to know cogni-
tive neuroscientists David Milner and Melvyn Goodale (2008). They studied a local woman,
D. F., who suffered brain damage when overcome by carbon monoxide, leaving her unable
to recognize and discriminate objects visually. Consciously, D. F. could see nothing. Yet she
exhibited blindsight — she acted as though she could see. Asked to slip a postcard into a
vertical or horizontal mail slot, she could do so without error. Asked the width of a block
in front of her, she was at a loss, but she could grasp it with just the right finger–thumb
distance. Likewise, if your right and left eyes view different scenes, you will be consciously
aware of only one at a time — yet you will display some blindsight awareness of the other
(Baker & Cass, 2013).
How could this be? Don’t we have one visual
Figure 1.5-3 system? Goodale and Milner knew from animal
research that the eye sends information simultane-
When the blind can “see” Copyright © Bedford, Freeman & Worth Publishers.
In this compelling demonstration ously to different brain areas, which support differ-
of blindsight and the two-track ent tasks (Weiskrantz, 2009, 2010). Sure enough, a
mind, researcher Lawrence scan of D. F.’s brain activity revealed normal activity
Weiskrantz trailed a blindsight in the area concerned with reaching for, grasping,
patient down a cluttered hallway.
Although told the hallway was and navigating objects, but damage in the area con-
empty, the patient meandered cerned with consciously recognizing objects. (See
around all the obstacles without another example in Figure 1.5-3.)
any awareness of them.
How strangely intricate is this thing we call
vision, conclude Goodale and Milner in their aptly
titled book, Sight Unseen (2004). We may think of
our vision as a single system that controls our visu-
ally guided actions. Actually, it is a dual-processing
system (Foley et al., 2015). A visual perception track
enables us “to think about the world” — to recog-
nize things and to plan future actions. A visual action
track guides our moment-to-moment movements.
The dual-track mind also appeared in a patient
dual processing the principle who lost all of his left visual cortex, leaving him blind to objects and faces presented on the
that information is often right side of his field of vision. He nevertheless could sense the emotion expressed in faces
simultaneously processed that he did not consciously perceive (de Gelder, 2010). The same is true of normally sighted
on separate conscious and people whose visual cortex has been disabled with magnetic stimulation. Such findings sug-
unconscious tracks.
gest that brain areas below the cortex process emotion-related information.
blindsight a condition in which Much of our everyday thinking, feeling, and acting operates outside our conscious
a person can respond to a visual
stimulus without consciously awareness (Bargh & Chartrand, 1999). Some “80 to 90 percent of what we do is uncon-
experiencing it. scious,” says Nobel laureate and memory expert Eric Kandel (2008). Sometimes our uncon-
scious biases (discomfort around someone of a different race or sexual orientation) do not

90 Unit 1 Biological Bases of Behavior

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