Maguire (2000) - Navigation ability

• biological approach

  → the study of the brain and the nervous system

  → investigates 'localisation of function' in the brain ,, i.e. which parts of the brain control specific behaviours

  → the approach assumes that ;

  • behaviour and experience can be affected by our biology - our brain and nervous system controls our behaviour
  • people are biological machines ,, controlled by chemicals like hormones and neurotransmitters
• the hippocampus


  → a structure in the brain ,, located in medial temporal lobe

  • part of limbic system ,, plays a key role in spatial memory and navigation - this is how you could draw the directions

  → previous research ; some animals have larger hippocampi volume ;

  • animals with a large territory have a larger hippocampi
  • small mammals who engage in lots of food storage
  • migrating birds
  • pigeons who fly long distances from unknown locations have larger hippocampi than other pigeon breeds
  • hippocampal volumes enlarge in some species during seasons when demand for spatial ability is greatest

  
• MRI scans


  → Magnetic Resonance Imagine (MRI) ;

  • provides 3D images of brain structures
  • uses magnetic fields and radio waves

  → MRI scans are analysed using ..

  • pixel counting (2D)
  • Voxel-based morphometry (3D)

  → therefore ,, pixel counting shown the area of a structure and VBM shows the volume or density
• aim


  → the aim of the study was to investigate whether changes could be detected in the brains of London taxi drivers and to further investigate the functions of the hippocampus in spatial memory
• method // procedure ; design

  → study is an example of a quasi experiment where the researchers compared the data of taxi drivers and non taxi drivers

  • researchers also made us of correlational analysis as they're investigating a relationship between the MRI scans and the length of time the taxi drivers had been licensed

  → matched pair design - match participants up with their characteristics they share ,, shows a clear comparison between groups
• method // procedure ; participants ~ 1


  → participants for this study were 16 healthy ,, right -handed male licensed London taxi drivers. the mean age of the taxi drivers was 44 years - range of ages was 32-62 years. all of the participants had been licensed London drivers for at least 1.5 years (mean time as taxi driver was 14.3 years - range was 1.4-42 years). the average time spent training to be a taxi driver before passing licensing tests fully (i.e. time spent on 'The Knowledge' was 2 years (range was 10 months - 3.5 years). some drivers were trained continuously and some part time
• method // procedure ; participants ~ 2


  → taxi drivers were compared to a control group of 50 healhy ,, right handed males who didn't drive taxis. MRI scans of 50 control p were selected from structural MRI scan database at same unit where taxi drivers were scanned. participants below 32 & above 62 yrs. age were excluded & females ,, left handed men & those with health issues. both mean age & age range didnt differ between taxi driver & control groups. researcher were careful to ensure an even spread of p in each decade

  → control group was as closely matched with taxi drivers as possible
• sample


  → 16 male London taxi drivers ;

  • all right handed
  • aged between 32-62 (mean aged 44)
  • licensed as taxi drivers for more than 1.5 years

  → 50 male non-taxi drivers ;

  • MRI scans taken from database
  • all healthy
  • all right handed ,, aged between 32-62
• procedure


  → data was collected using MRI scans which collects data about the structure or anatomy of the brain

  • collected using structural MRI scans of the taxi drivers and non-taxi drivers

  → scans were analysed using 2 techniques ;

  • VBM - Voxel Based Morphometry ; used to measure density of grey matter in the brain ,, provides a 3D measurement of volume of an area
  • Pixel counting ; 2D measurement of an area - were calculated by taking images of slices of whole length of hippocampus

  → 24 'slices' of the hippocampus ;

  • 6 - rear hippocampus ,, 12 - hippocampus body & 6 - front hippocampus
• controls


  → the same MRI scanner was used for all participants

  → pixel counting was done by a 'blind' researcher ;

  • didn't know aims of the research ,, or who's scan they were analysing

  → the hippocampal volume for each participant was calculated to include an adjustment for the size of each people's brain. this was to ensure that all participants data was comparable
• results - overall

  TAXI drivers ;

  → POSTERIOR HIPPOCAMPUS ;

  • taxi drivers - larger grey matter volume than controls (in both left & right hippocampi)
  • controls - smaller grey matter volume than taxi drivers (in both left & right hippocampi)

  → ANTERIOR HIPPOCAMPUS ;

  • taxi drivers - smaller grey matter volume than controls (in both left & right hippocampi)
  • controls - larger grey matter volume than taxi drives (in both left & right hippocampi) ,, higher volume in right hippocampi than left

  → ELSEWHERE IN THE BRAIN ;

  • no differences between taxi drivers and the control group
• results ; VBM // pixel counting

  → taxi drivers had significantly increased grey matter in the right & left hippocampi

  • no differences anywhere else in the brain

  → also ,, no differences in total hippocampi volume. however ;

  • in the taxi drivers ,, the posterior hippocampi was larger than the controls
  • in the controls ,, there was more grey matter in the anterior hippocampi than the taxi drivers

  → also ,, in the controls ,, their anterior hippocampi was larger on the right than the left
• correlation ;


  → 1st graph ;

  • positive correlation - as length of time as taxi driver increases ,, right posterior hippocampal volume increases

  → 2nd graph ;

  • negative correlation - as length of time as taxi driver increases ,, right anterior hippocampal volume decreases

  
• explanation of findings ; 1

  → 'professional dependence on navigaitional skills in licensed London taxi drivers is associated with a relative redistribution of grey matter in the hippocampus'

  → results suggest plasticity of the hippocampi ;

  • structural changes as a result of experience

  → ANTERIOR HIPPOCAMPUS ;

  • may be involved in encoding new information

  → POSTERIOR HIPPOCAMPUS ;

  • seems to be related to previously learned spatial information
• explanation of findings ; 2

  → 'professional dependence on navigaitional skills in licensed London taxi drivers is associated with a relative redistribution of grey matter in the hippocampus' ;

  → LEFT HIPPOCAMPUS ;

  • wasn't correlated at all with length of taxi driving experience. possible role - to store memory of people & events associated with the content of taxi driving

  → RIGHT HIPPOCAMPUS ;

  • this was positively correlated with length of taxi driving experience. seems to integrate information into a 'mental map'
• evaluation ; STRENGTH ~ 1

  → MRI scans provided researchers with vast amounts of quantitative data relating to volume and size of the hippocampus enabling them to carry out statistical analysis such as correlational analysis - can easily draw comparisons between hippocampi of taxi and non-taxi drivers

  → study empolyed many controls - E.G. samples were matched for age ,, sex and handedness. the pixel counting was carried out by a researcher who was experienced in this technique but 'blind' to the participants conditions - therefore prevented variables from influencing the results of the study
• evaluation ; STRENGTH ~ 2

  → MRI scanning technology doesn't pose any health risks to the participants ,, and all of the participants gave informed consent. none of the participants should have been negatively affected by their experience ,, so it was an ethical study
• evaluation ; WEAKNESS ~ 1

  → the task of being scanned in an MRI scanner is hardly ecologically valid. however ,, it would not be possible for the participants to respond to demand characteristics. MRI scanning is also a costly technique in terms of expensive equipment and researchers' time ,, although the use of computers does make very sophisticated analysis possible

  → an obvious weakness is that all the participants were male and right handed - not generaliseable to other populations
• evaluation ; WEAKNESS ~ 2

  → it's normally difficult to make conclusions from quasi experiments as as any differences found between the 2 groups may not have occured because of the IV. E.G. - it could be possible that people with certain brain differences are attracted to certain jobs

  • however ,, researchers carried out correlational analysis - clearly demonstrates that there was a pos correlation between length of time participants had been driving cabs & their posterior hippocampal volume - suggests that length of time taxi driving is associated with increased grey matter in the hippocampus