So, if my right thumb emerged on top, I was a coldly logical and rational person, likely to excel in the pure sciences (a dominant left brain); conversely, if it were my left thumb, I was an imaginative, creative and emotionally inclined person and, of course, likely to excel in the arts (a dominant right brain). And this claimed to be a class of second year psychology! Popular debate, self help books, even articles on management are replete with references to this rather romantic conception of specialization or 'lateralization' of brain function.
What is the 'split brain hypothesis'? The idea can be traced to the 'split brain experiments' by the Nobel prize winning neurologist, Roger Sperry. These experiments involved epileptic patients, who had (as a part of their treatment) had their corpus callosum (the thick band connecting the left and the right hemispheres of the brain) surgically removed...(hence the usage of the term 'split brain'). Consequently, in these 'split brain patients', neither hemisphere of the brain had access to what the other hemisphere already 'knew'. It is in these experiments that evidence of lateralization or the specialization of each cerebral hemisphere in certain functions was first found.
When an object (a fork) was placed in the left visual field of the 'split brain patient'( ie when his "right brain" was operating without help from the left), he was unable to name the object. When, however, he was asked to pick up the same object, he was able to do so with his left hand. On the other hand, when the object was placed in his right visual field ("left brain" operating without help from the right), the patient could name the object, but was unable to pick it up with his right hand. These results pointed to a certain degree of specialization: at a rudimentary level, of the right brain in controlling motor activity and of the left brain in controlling language. Similar experiments supported the notion that the left brain tends to organize through logical categories and the right brain tends to resort to mental imagery and spatial perception. For instance, when a split brain patient was asked to associate a cake kept on a plate with a picture, his left brain associated it with the picture of a fork and a spoon (logical connection by function), while his right brain associated it with the picture of a hat!(similarity in appearance)
However, subsequent research involving brain scanning techniques has revealed that the difference in the functioning of the two cerebral hemispheres lies in their processing style ie rather than specializing in particular processes, the two cerebral hemispheres use different techniques for performing the same process. While, the left hemisphere focuses on and processes by detail, the right hemisphere focuses on the larger picture. This is typically why the left hemisphere is found to be relatively specialized in verbal and analytical reasoning (detailed, step by step analysis), while the right hemisphere is found to be more adept at spatial perception or the figurative usage of speech (necessary, for instance, in understanding jokes and proverbs).
In every individual, both the hemispheres of the brain contribute to every mental activity. In every individual, for every mental activity, it is necessary that the left hemisphere work in its unique processing style, just as it is necessary that the right hemisphere apply its processing style. The exclusive control of one hemisphere over certain activities like logical or creative thinking is, therefore, a myth, with each activity requiring the complementary functioning of both the hemispheres.
Returning to the chirpy and 'intrinsically motivated' psychologists, it is my sincere hope, that their cherished notion of the logical-rational 'left brain dominant person' and the creative-imaginative 'right brain dominant person' will only continue to find resonance in pop psychology.
