<P> The same effect occurs for visual pairs and reasoning . For example, a patient with split brain is shown a picture of a chicken foot and a snowy field in separate visual fields and asked to choose from a list of words the best association with the pictures . The patient would choose a chicken to associate with the chicken foot and a shovel to associate with the snow; however, when asked to reason why the patient chose the shovel, the response would relate to the chicken (e.g. "the shovel is for cleaning out the chicken coop"). </P> <P> "Scientists have often wondered whether split - brain patients...are' of two minds"' (Zilmer, 2001). However, recent evidence has emerged that despite lack of communication between the two cereberal hemispheres, consciousness appears to still take a unified state . </P> <P> In the 1950's, research on people with certain brain injuries made it possible to suspect that the "language center" in the brain was commonly situated in the left hemisphere . One had observed that people with lesions in two specific areas on the left hemisphere lost their ability to talk, for example . Roger Sperry and his colleague pioneered research . In his early work on animal subjects, Sperry made many noteworthy discoveries . The results of these studies over the next thirty years later led to Roger Sperry being awarded the Nobel Prize in Physiology or Medicine in 1981 . Sperry received the prize for his discoveries concerning the functional specialization of the cerebral hemispheres . With the help of so - called "split brain" patients, he carried out experiments, and for the first time in history, knowledge about the left and right hemispheres was revealed . In the 1960s Sperry was later joined by Michael Gazzaniga a psychobiology Ph. D. student in his work on split - brain research at Caltech in Pasadena, California . Even though Sperry is considered the founder of split - brain research, Gazzaniga's clear summaries of their collaborative work are consistently cited in psychology texts . In Sperry and Gazzaniga's "The Split Brain in Man" experiment published in Scientific American in 1967 they wanted to explore the extent to which two halves of the human brain were able to function independently and whether or not they had separate and unique abilities . They wanted to examine how perceptual and intellectual skills were affected in someone with a split - brain . At Caltech, Gazzaniga worked with Sperry on the effects of split - brain surgery on perception, vision and other brain functions . The surgery, which was a treatment for severe epilepsy, involved severing the corpus callosum, which carries signals between the left - brain hemisphere, the seat of speech and analytical capacity, and the right - brain hemisphere, which helps recognize visual patterns . At the time this article was written, only ten patients had undergone the surgery to sever their corpus callosum (corpus callosotomy). Four of these patients had consented to participate in Sperry and Gazzaniga's research . After the corpus callosum severing all four participants personality, intelligence, and emotions appeared to be unaffected . The testing done by Sperry and Gazzaniga showed however, the subjects demonstrated unusual mental abilities . The researchers created three types of tests to analyze the range of cognitive capabilities of the split - brain subjects . The first was to test their visual stimulation abilities, the second test was a tactile stimulation situation and the third tested auditory abilities . </P> <P> The first test started with a board that had a horizontal row of lights . The subject was told to sit in front of the board and stare at a point in the middle of the lights, then the bulbs would flash across both the right and left visual fields . When the patients were asked to describe afterward what they saw, they said that only the lights on the right side of the board had lit up . Next when Sperry and Gazzaniga flashed the lights on the right side of the board on the subjects left side of their visual field, they claimed to not have seen any lights at all . When the experimenters conducted the test again, they asked the subjects to point to the lights that lit up . Although subjects had only reported seeing the lights flash on the right, they actually pointed to all the lights in both visual fields . This showed that both brain hemispheres had seen the lights and were equally competent in visual perception . The subjects did not say they saw the lights when they flashed in the left visual field even though they did see them because the center for speech is located in the brain's left hemisphere . This test supports the idea that in order to say one has seen something, the region of the brain associated with speech must be able to communicate with areas of the brain that process the visual information . </P>

Who performed the first successful split brain surgery
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