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Module 1.4c



                                                                                                        Figure 1.4-21
                                                                                                        One skull, two minds
                                                                                                        When an experimenter flashes
                                                                                                        HE•ART across the visual field,
                                                                                                        a woman with a split brain
                                                                                                        verbally reports seeing the
                                                                                                        word transmitted to her left
                                                                                                        hemisphere. However, if asked
                                                                                                        to indicate with her left hand
                                                                                                        what she saw, she points to the
                                                                                                        word transmitted to her right
                                                                                                        hemisphere (Gazzaniga, 1983).
                             “Look at the dot.”                 Two words separated by a dot
                                 Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
                                                                are momentarily projected.
                                  (a)                                    (b)

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                                    “What word did you see?”  or  “Point with your left hand
                                                                 to the word you saw.”
                                                          (c)

                      their left hand to what they had seen, they were startled when their hand (controlled by the
                      right hemisphere) pointed to HE. Given an opportunity to express itself, each hemisphere
                      indicated what it had seen. The right hemisphere (controlling the left hand) intuitively knew
                      what it could not verbally report.
                          When a picture of a spoon was flashed to their right hemisphere, the patients could
                      not say what they had viewed. But when asked to identify what they had viewed by feeling
                      an assortment of hidden objects with their left hand, they readily selected the spoon. If the
                      experimenter said, “Correct!” the patient might reply, “What? Correct? How could I possi-
                      bly pick out the correct object when I don’t know what I saw?” It is, of course, the left hemi-
                      sphere doing the talking here, bewildered by what the nonverbal right hemisphere knows.
                          A few people who have undergone split-brain surgery have been for a time bothered by
                      the unruly independence of their left hand. It was as if the left hand truly didn’t know what
                      the right hand was doing. The left hand might unbutton a shirt while the right hand buttoned
                      it, or put grocery store items back on the shelf after the right hand put them in the cart. It was
                      as if each hemisphere was think-
                      ing, “I’ve half a mind to wear my                                                 Figure 1.4-22
                      green (blue) shirt today.” Indeed,                                                Try this!
                      said Sperry (1964), split-brain sur-                                              People who have had split-brain
                      gery leaves people “with two sep-                                                 surgery can simultaneously draw
                      arate minds.” With a split brain,                                                 two different shapes.
                      both hemispheres can compre-
                      hend and follow an instruction to
                      copy — simultaneously —  different
                      figures with the left and right
                      hands (Franz et al., 2000; see also
                      Figure 1.4-22). Today’s researchers

                                                                    The Brain: Damage Response and Brain Hemispheres  Module 1.4c   83






          03_myersAPpsychology4e_28116_ch01_002_163.indd   83                                                                   15/12/23   9:23 AM
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