Sperry (1968) Split brain study

spary 1968 split brain study background the biological approach to psychology is primarily focused on the relationship between our human autonomy and our behavior and experiences the approach has led to many useful discoveries such as how the nervous system and various chemicals can have a big effect on our behavior as well as advances in medical treatment for example MRI scanners which can detect various conditions and activities in the brain one such discovery led to a groundbreaking new treatment for people who suffer from epilepsy people who suffer from epilepsy can have episodes of fits or seizures which are caused by a sudden burst of electrical activity in the brain the epilepsy occurs when the electrical storm travels from one hemisphere of the brain to the other causing the entire brain to be affected and causing an epileptic episode it was discovered that the main region of the brain responsible for connecting the left and the right hemisphere of the brain is the corpus colosum which is a large band of white matter located in the center and that when this is severed it can reduce and even prevent epilepsy in patients this procedure continues to be used today for severe cases of epilepsy however it does come with additional side effects the brain is composed of two distinct hemispheres which both specialize in different types of information generally the left side control speech language arithmetic and comprehension and is sometimes known as the analytical or logical brain while the right side controls creativity artistic ability and intuition and is often known as the creative brain brains are also contralateral which means that information that enters your senses on the left side of your body gets processed by the right brain hemisphere an information entering senses on your right side gets processed by left brain hemisphere the brain is usually able to share information between two hemispheres via the corpus colosum however for people whose brain has been split the brain cannot do this as easily the researchers in spari study of patients with split brains wanted to investigate the implications of the procedure on their abilities aim spari wanted to investigate how each hemisphere of the brain processes independent streams of consciousness and memories and how this impacts the ability of split brain patients sample the study used a total of 11 participants all of whom had previously undergone a split brain surgery to help treat their severe cases of epilepsy or participants had had their surgeries at varying times ranging between five and a half years before the study and just a few weeks or months methodology spari study was a quasi experiment which took place in a laboratory using an independent measures design the independent variable was whether or not participants had a split brain however there was no control group that was measured during the experiment since the effects of not having a split brain were already known the dependent variable was the performance of participants on the tactile and visual tasks in the experiment procedure the visual tasks that spari devised consisted of having the participants sit at a table in front of a screen participants were instructed to stare at a focal point in the center of the screen while having one eye covered the researcher would then project images and other visual stimuli onto either the left side of the screen or the right depending on which corresponding eye the participant had open however at least one of the visual tasks involved stimuli being presented to both sides all of the visual stimuli that were projected onto the screen was only shown for one tenth of a second to ensure that the stimuli only entered the intended visual field left or right the dollar sign and question mark task involved a dollar sign and a question mark being presented to the screen simultaneously one to the left visual field and one to the right and then the participants were tested on what they had seen during the tactile tasks the participants were instructed to put their hands under the screen so that they could touch a number of objects on the other side which they couldn't see the experimental would place objects into the participants hands then ask them to describe them results for the visual tasks it was found that the participants ability to reliably identify the stimuli presented to them was severely impaired in one of the tasks where lights were flashed from the left visual field of the screen to the right the participants reported only seeing lights flash up on the right side however when the right eye was covered and the lights were flashed to the left visual field the participants claimed to have not seen any lights whatsoever but when asked a point at which side the lights had flashed they could do so another finding was that participants could only recognise visual stimuli that had been presented previously if it was shown to the same side for example if they were shown stimuli to the right visual field and then subsequently shown the same stimuli in the left field they would claim that they had not seen it before it was further found that stimuli presented to the right visual field which is connected to the left brain hemisphere responsible for speech and language participants could describe what they had seen in speech and writing with their right hand if the same stimuli was presented to their left visual field which is linked to the right brain hemisphere responsible for creativity and intuition they would either insist they didn't see anything or that stimuli was only present on the right visual field which they hadn't seen however the participants were able to nonverbly indicate which stimuli they had seen by pointing with their left hand in the dollar sign and question mark task where a dollar sign was shown to the left visual field and a question mark shown to the right visual field it was found that participants would draw a picture of the dollar sign when asked to draw what they had seen but when asked to verbally identify what they had seen they would report having seen a question mark similarly with the tactile tasks any object that were placed in the participants right hand could be accurately described even verbally or through writing however if those same objects were placed in the participants left hand they could only make guesses about what they were holding and often seemed unaware that they were even holding anything at all objects that had previously been held would only be recognised again by the same hand for example any objects that had only been handled by the left hand were not recognised by participants as being an object that they had previously held when they held it with their right hand when two different objects were placed in each hand of the participant and then hidden in the pile of objects both hands could only identify the object that it had held and ignored the other hands object conclusions the researchers concluded that the brains of split room patients have lost the ability to cross integrate information from one hemisphere to the other this means that they seem to have two independent streams of consciousness each with a set of perceptions memories impulses and abilities almost like two independent minds in one body the fact that participants brains were split meant that any stimuli that was presented to one hemisphere was not processed by the other hemisphere due to the distinct roles of each hemisphere the loss of cross integration manifested as the inability of the participants to verbally describe or describe in writing any stimuli that was presented to their left visual field despite the fact that they could still non-verbally identify that same stimuli by pointing at it with their left hand this shows that in order to verbally describe something the region of the brain associated with language has to be able to communicate with the region that processes stimuli for that specific field either left or right evaluations the study was a quasi experiment since the independent variables occurred naturally and were not manipulated by the researchers this makes it more difficult to establish cause and effect compared with the traditional laboratory experiment due to the low level of control the researchers also decided not to use a control group specifically within the experiment which reduces the study's validity since there was no separate condition to compare the split brain patients results to however the researchers did state that a control group was not needed since the results of healthy people without a split brain were already known the study's external validity and ecological validity was quite low since stimuli was deliberate since stimuli was deliberately only delivered to one hemisphere by using an eye covering to prevent stimuli from being processed by both this would not usually happen in the participants every day lives since they would normally use both eyes to process stimuli from the world around them which would negate the fact that they had lost the ability to cross integrate information between hemispheres the sample consisted of 11 participants which is a relatively small sample due to the rarity of split brain patients the participants had also previously suffered from another neurological problem in the form of epilepsy which may have acted as a confounding variable and also means that we should be careful in generalizing the study's findings the researchers ensured that participants used eye coverings which improved the level of control in the study by preventing stimuli from being processed by both the participants hemispheres the study was also fairly ethical since no variables were manipulated in the experiment and the participants split brains were naturally occurring participants were also not deceived and were able to give their consent before taking part in in the study.