Hemispheric lateralisation Flashcards
What is hemispheric lateralisation ?
Each hemisphere has a specific function
What is the left hemisphere used for ?
Language - where the two language centres are located
What is the right hemisphere used for ?
Visual and spatial dominant
What was Fink’s study ?
- Conducted PET scans of participants during processing tasks
- When looking at the whole picture, the right hemisphere was highly active
- When focusing on small, fine details, the left hemisphere was highly active
- Visual processing is therefore lateralised
What was Nielson’s study ?
- analysed brain scans of 1000 participants aged 7-29
- There was evidence of lateralisation, however there was no evidence of dominant hemispheres (being right or left brained)
Counterpoint: Only looking at young brains
Szarflacki - lateralisation decreases with age
What has happened to people with split brains ?
- They have a severed corpus callosum
- This is the part between the two hemispheres
- The two hemispheres therefore cannot communicate
What was the basis of Sperry and Gazzaniga’s study ?
- Investigated hemispheric lateralisation in 11 split brain patients
- Had their corpus callosum out (comissurotomy) due to severe epilepsy
- Quasi experiment - naturally occurring independent variable
What were the 4 different tasks in Sperry ?
- Describing tasks - Asked if they could describe what they saw (meant to describe a smiley face)
- Tactile task - Touching a key, had to describe what it was and then find one that felt the same
- Drawing task - had to draw a smiley face
- Composite task - Given two different words and asked why they drew/wrote what they did
What were the findings of the describing task ?
Right hemisphere = Couldn’t describe what they saw because the right side is visual dominant and has limited language use
Left hemisphere = Could describe what the can see due to the two language centres located in the left hemisphere
What were the findings of the tactile task ?
Right hemisphere = Couldn’t describe due to visual dominant side.
But they could kind another key due to their somatosensory cortex which is used by both sides
Left hemisphere = Could describe what they could see.
Used the somatosensory cortex to find the key
What were the findings of the drawing task ?
Right hemisphere = Drawn with left hand - better with visual tasks - able to draw accurately
Left hemisphere = Drawn with the right hand - less capable with visual tasks - tried to drawn but wasn’t accurate.
What were the findings of the composite task ?
Right hemisphere = Saw the word key and drew a key
Left hemisphere = Saw the word ring and wrote the word ring.
When they were asked about why they drew and wrote the pictures and words they couldn’t say why. This is because the two sides can’t communicate due to the severing of the corpus callosum.
Why is artificial task a limitation of Sperry’s study ?
- The study has limited ecological value
- The tasks aren’t realistic
- The board used to split the sides also isn’t applicable to real-life
- In real-life both hemispheres are used just separtely
Why is generalisability a limitation of Sperry’s study ?
- You can’t generalise this to every human as these participants had unique conditions
- They were also all right handed which affects the drawing task
- Means there is little application wide-scale due to a small sample size
What is a supporting study of Sperry’s study ?
Luck
- Found that split brain patients performed better than the control groups in certain tasks
- E.g identifying the odd one out using the left hemisphere
- Supports that two-sides of the brain are separate and distinct
