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believe that a split-brain patient’s mind resembles a river that has branched into separate
streams, each unaware of its influence on the other (Pinto et al., 2017). (Reading these reports,
TEACH 1.4-9 can you imagine a patient enjoying a solitary game of “rock, paper, scissors” — left versus right
hand?)
Teaching Tip When the “two minds” are at odds, the left hemisphere does mental gymnastics to
Students often leave this section with rationalize reactions it does not understand. If a patient follows an order (“Walk”) sent
to the right hemisphere, a strange thing happens. The left hemisphere, unaware of the
the impression that life is difficult for order, doesn’t know why the patient begins walking. But if asked, the patient doesn’t reply,
split-brain individuals. In fact, they “I don’t know.” Instead, the left hemisphere improvises — “I’m going into the house to get a
experience difficulty only in the first Coke.” Gazzaniga (2006), who described these patients as “the most fascinating people on
earth,” realized that the conscious left hemisphere resembles an “interpreter” that instantly
months after surgery. As time passes, constructs explanations. The brain, he concluded, often runs on autopilot; it acts first and
the “two separate minds” begin to then explains itself.
figure out how to work together. Help
students understand that split-brain
individuals do not experience prob- AP Science Practice Check Your Understanding
®
lems in daily life because the optic
chiasm is not severed in the surgery. Examine the Concept Apply the Concept
▶
▶(a) If we flash a red light to the right hemisphere of a person
▶Explain what is meant by split brain.
▶
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
The optic chiasm (covered in more ▶ ▶Explain the classic split-brain studies. with a split brain, and flash a green light to the left hemisphere,
detail in Module 1.6b) is the place will each hemisphere observe its own color? (b) Will the person
be aware that the colors differ? (c) What will the person verbally
where the nerves connecting the eyes report seeing?
and the brain cross, leading to cross- ▶ ▶Can you put yourself in the shoes of a patient with a split
brain? What would it be like to have knowledge which you were
hemispheric processing. Because unaware of and couldn’t verbally report but were nevertheless
split-brain individuals do receive visual able to act on?
information from both visual fields, the Answers to the Examine the Concept questions can be found in Appendix C at the end of the book.
abnormalities are only noticeable in
specialized laboratory conditions.
Right–Left Differences in the Intact Brain
So, what about the 99.99+ percent of us with undivided brains? Does each of our hemi-
spheres also perform distinct functions? The short answer is Yes. When a person performs
ENGAGE 1.4-9 a perceptual task, a brain scan often reveals increased activity (brain waves, blood flow, and
glucose consumption) in the right hemisphere. When the person speaks or does a math
(15 minutes) Have students search calculation, activity usually increases in the left hemisphere.
the internet for educational programs A dramatic demonstration of hemispheric specialization happens before some types of
brain surgery. To locate the patient’s language centers, the surgeon injects a sedative into
that sell themselves as “educating Copyright © Bedford, Freeman & Worth Publishers.
the neck artery feeding blood to the left hemisphere, which usually controls speech. Before
both sides of your brain.” Even though the injection, the patient is lying down, arms in the air, chatting with the doctor. Can you
this myth has been debunked, it is still predict what happens when the drug puts the left hemisphere to sleep? Within seconds,
quite prevalent. After 10 minutes of the person’s right arm falls limp. If the left hemisphere is controlling language, the patient
will be speechless until the drug wears off. If the drug is injected into the artery to the right
searching, have students report back hemisphere, the left arm will fall limp, but the person will still be able to speak.
to the class. Tie their examples back To the brain, language is language, whether spoken or signed. (See Module 3.5 for
into a discussion of the intact brain. more on how and where the brain processes language.) Just as hearing people usually use
the left hemisphere to process spoken language, deaf people use the left hemisphere to
process sign language (Corina et al., 1992; Hickok et al., 2001). Thus, a left hemisphere
stroke disrupts a deaf person’s signing, much as it would disrupt a hearing person’s
TEACH 1.4-9 speaking (Corina, 1998).
Enrichment 84 Unit 1 Biological Bases of Behavior
Is language only located in the left
hemisphere? Share with your stu-
dents the case of V. J. (reported by can say it but not write it. This is the first clear TEACH 1.4-9 15/12/23 9:23 AM
03_myersAPpsychology4e_28116_ch01_002_163.indd 84
Michael Gazzaniga), a left-handed scientific evidence that in some people the
and divided-brain woman whose capacities for spoken and written language Teaching Tip
case challenges notions of where the may be located in different hemispheres. Help students see that basic language pro-
capacity for language resides. When Linguist Steven Pinker thinks that V. J.’s case cessing is a left-hemisphere activity, as the
a word is presented to her left visual provides evidence that reading and writing textbook points out by citing research that
field and thus processed by the right arose separately from spoken language and deaf people process sign language in the
half of her brain, she can write it but may be wired into the brain wherever there left hemisphere. However, notice in the other
not say it. When a word is presented are “spare areas.” citations that the right hemisphere is respon-
to her right visual field and thus pro- sible for more complex understandings and
cessed by the left hemisphere, she interpretations of language. Working together,
the hemispheres help us have a rich, complex
understanding of language.

84 Unit 1 Biological Bases of Behavior

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