改变心理学的40项研究(第8版,英文版)

You are probably aware that the two halves (or hemispheres) of your brain are not the sameand that they perform different functions. For example, in general, the left side of yourbrain is responsible for movement on the right side of your body, and vice versa. Beyondthis, though, the two brain hemispheres have much more elaborate specialized abilities. It has come to be rather common knowledge that for most of us, the left braincontrols our ability to use language while the right is involved in spatial relationships,such as those needed for artistic activities. Stroke or head-injury patients who sufferdamage to the left side of the brain will often lose, to varying degrees, their ability tospeak (often this skill returns with therapy and training). Some researchers believe thateach hemisphere of your brain may actually be a separate mental system with its ownindividual abilities for learning, remembering, perceiving the world, and feeling emotions. The concepts underlying this view of the brain rest on early scientific research onthe effects of splitting the brain into two separate hemispheres. This research was pioneered by Roger W. Sperry (1913–1994), beginning about15 years prior to the article examined in this chapter. In his early work with animalsubjects, Sperry made many remarkable discoveries. For example, in one series of studies, cats’brains were surgically altered to sever the connection between the two halvesof the brain and to alter the optic nerves so that the left eye transmitted informationonly to the left hemisphere and the right eye only to the right hemisphere. Following surgery, the cats appeared to behave normally and exhibited virtually with no illeffects. Then, with the right eye covered, the cats learned a new behavior, such as walking through a short maze to find food. After the cats became skilled at maneuveringthrough the maze, the eye cover was shifted to the cats’ left eyes. Now, when the catswere placed back in the maze, their right brains had no idea where to turn, and theanimals had to relearn the entire maze from the beginning. Sperry conducted many related studies over the next 30 years, and in 1981 hereceived the Nobel Prize for his work on the specialized abilities of the two hemispheresof the brain. When his research endeavors turned to human participants in the early1960s, he was joined in his work at the California Institute of Technology (Caltech) by Michael Gazzaniga. Although Sperry is considered to be the founder of split-brain research, Gazzaniga’s article has been chosen here because it is a clear, concise summary of their early collaborative work with human participants and it, along with other related research by Gazzaniga, is cited often in psychology texts. Its selection is in no way intended to overlook or overshadow either Sperry’s leadership in this field or his great contributions. Gazzaniga owes his early research, and his discoveries in the area of hemispheric specialization, to Roger W. Sperry (see Sperry, 1968; Puente, 1995). To understand split-brain research, some knowledge of human physiology isrequired. The two hemispheres of your brain are in constant communication with oneanother via the corpus callosum, a structure made up of about 200 million nerve fibers(Figure 1.1.1). If your corpus callosum is cut, this major line of communication is disrupted, and the two halves of your brain must function then independently. If we wantto study each half of your brain separately, “all” we need to do is surgically sever yourcorpus callosum.