Hemispheric lateralisation and split brain research Flashcards
What is lateralisation?
The idea that two halves of the human brain are not exactly alike - each hemisphere has functional specialisation
What do each of the hemispheres specialise at?
Left - language and speech
Right - visual / motor tasks
How are the hemispheres connected?
Through the corpus callosum
What is the main advantage of lateralisation?
Increases neural processing capacity
By using only one hemisphere to engage in a particular task this would leave the other hemisphere free to engage in another function
What did Rogers et al (2004) find?
Found that in domestic chickens brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously - finding food and being vigilant for predators.
What did Tonnessen et al (1993) find ?
Found a small but significant relationship between handedness and immune disorders, suggesting that the genetic process that leads to lateralisation may also affect the development of the immune system
Does lateralisation of function stay the same or change throughout our lives ?
Changes with normal ageing - across many types of task and many brain areas, lateralised patterns found in younger adults tend to switch to bilateral patterns in healthy older adults
What did Szaflarski et al (2006) find?
Found that language became more lateralised in children and adolescents but after the age of 25 lateralisation decreased with each decade of life
What does a ‘split brain’ operation involve?
Severing the connections between the right hemisphere and the left hemisphere, mainly the corpus callosum.
What does split brain research study?
How the hemispheres function when they can’t communicate with each other
What was the aim of Sperrys study?
The aim of the study was to record the psychological effects of hemispheric deconnection and to find evidence for lateralisation of function in “normal brains “.
What was the sample in sperrys study?
11 people, both male and female who has the split brain operation because they had previously suffered with severe epilepsy
What was the visual field task in sperrys study?
An image could be projected to a ppts RVF (processed by LH) and the same, or different, image could be projected to the LVF (processed by the RH). In the normal brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture of the visual world. However, presenting the image to one hemisphere of a split-brain participant meant that the information cannot be conveyed from that hemisphere to another
What was the result of the visual task in Sperry’s study?
When participants were shown an image in their RVF this image would be processed in the left hemisphere which is in charge of language and therefore the participant would be able to see and write what they had seen. When participants were shown an image in their LVF this image would be processed in the right hemisphere which is in charge of spatial awareness therefore they wouldn’t be able to say the word but they could draw it.
What was the result if a pinup picture was shown to the LVF?
An emotional reaction (eg. A giggle) but the participants usually reported seeing nothing or just a flash of light
What can we conclude from Sperry’s study?
Split brain patients appear to have two independent streams of consciousness, each with its own memories, perceptions and impulses: effectively, two minds in one body. This supports the argument of lateralisation of function.
Evaluate Sperry’s study - ecological validity and mundane realism
Sperry’s research was conducted under lab conditions which are artificial, meaning that the results lack mundane realism.
It would be very rare for a split brain patient to just use one visual field and therefore present information to just one visual field in real life, therefore it can also be criticised for lacking ecological validity.
Evaluate Sperry’s study: generalisability
There are very few of these patients, and only 11 were present in Sperry’s study. This is a very small sample size so can be said to lack generalisability to the target population.
Evaluate Sperry’s study: individual differences
Sperry failed to control for individual differences and the participants in his study differed in age, gender, handedness, age at which they developed epilepsy etc. This means that patients may have developed strategies to compensate for the effects of the operation therefore meaning that Sperry’s findings would lack validity.
