Maguire

• Background

  Maguire was inspired by previous research that had been done, specifically by Blakemore and Cooper about functional brain plasticity, however, she wanted to expand on this and research structural brain plasticity.

  
  

  She wanted to investigate the hippocampus, which is a major part of the limbic system in charge of navigation.

  
  

  Previous research had suggested that the hippocampi of some animals grows in size during times when their navigational and special reasoning skills are exercised more often.

  
  

  However, there had been no research illustrating whether human brains would plasticise as a result of environmental changes, therefore, Maguire wanted to investigate this further and the best people to use were London Taxi Driver as they had to learn 'The Knowledge' of London and had much navigational experience.
• Aim

  To investigate the differences in the brains of London taxi drivers and a control group who were not taxi drivers (volume of the hippocampus)
• Sample

  experimental group:

  - 16 male taxi drivers

  - healthy, all right handed

  - mean age 44 years

  - taxi driver job during 14.4 years

  
  

  control group:

  - 16 male non taxi drivers

  - all right handed

  - mean age 44 years

  - no medical, neurological or psychological health problems
• Research method

  - matched participants with independent measures

  - quasi experiment

  - IV = whether p's are taxi driver or non taxi drivers

  - DV = volume of hippocampus (grey matter)
• Procedure

  MRI scans of all p's were analysed using:

  -> VBM (automatic procedure that 'normalises' the scans to a template to eliminate overall brain size as a variable) = brains of 16 taxi driver was compare to 16 non taxi drivers to see if there was a difference in structure

  
  

  -> pixel counting compared vol of anterior, body + posterior cross-sections of taxi drivers hippocampus

  
  

  images were analysed by one person (low concurrent validity/inter-rater) experienced in technique + objective analysis = allows total hippocampal volume to be calculated
• Results

  VBM analysis showed no sig difference between brains of the two groups except

  -> taxi drivers had increased grey matter vol in right + left posterior hippocampus

  
  

  Pixel counting showed although no sign diff in overall volume of hippocampi

  -> taxi drivers had sig greater posterior hippocampal volume than controls
• Conclusions

  - there are regionally specific structural differences between the hippocampi of taxi drivers compared to those who are not

  -> shows evidence of brain plasticity/ changes of hippocampal grey matter are acquired due to nurture

  
  

  - clear evidence that environment experience (regular navigation) can cause structural brain plasticity
• Link to biological approach

  Biological psychologists suggest that although behaviour had a physiological origin and genetic information is inherited, the environment an individual is in can alter how genetics are demonstrated (1).

  
  

  Maguire's study examined structural brain plasticity in London taxi-drivers vs non-taxi drivers, and found that taxi drivers had significantly greater grey matter volume in their posterior hippocampus (responsible for spatial navigation of routes already visited) in comparison to controls (1).

  
  

  Maguire thereforelinks to the biological approach as she explores the innate brain region of the hippocampus, which is part of everyone's physiology; yet the way in which the volume of this region of the brain plasticises is due to the environmental experiences we have e.g. taxi drivers have vast navigational experience of London, leading to increased volume in this region(2)
• Link to key theme of 'brain plasticity'


  She found that the volume of the posterior hippocampi of the taxi drivers was larger than the control group, linking to thekey theme of brain plasticity as this clearly illustrates that structural brain plasticity can occur based on environmental navigational experience
• Ethics (followed + broken)

  + deception

  + informed consent (volunteer sample)

  
  

  - MRI may cause anxiety + emotional harm = protection of p's violated
• Reliability

  Internal:

  + highly standardised procedure

  -> eg. all of the men had the same MRI scan + same software was used to analyse scans

  
  

  External:

  + collects quant data = if study was replicated the same results could be gathered

  + scientific + objective equipment = MRI scanner to check for consistency of data

  - sample of men was quite small + no women were used = no room for wide comparison of female hippocampal volume
• Validity

  + removes individual differences = matched on gender, age

  
  

  + researcher was blind to conditions

  
  

  + no risk of demand characteristics = p's cannot falsify their hippocampal volume although lab experiment

  
  

  - low ecological validity = p's wouldn't usually have an MRI scan in their daily lives as taxi drivers
• Sample evaluation

  + no gender bias = males were used to remove EV's

  
  

  - unsure of the brain plasticity of female taxi drivers

  
  

  - not typical of general population + brain plasticity = everyone's brain may not respond in the same way to the environment demands of doing 'the knowledge
• Research method evaluation

  + high control over EVs

  -> matched on key characteristics that could affect the hippocampus eg. age, gender

  -> removes individual differences

  
  

  + correlational analysis to establish relationship between volume of grey matter

  -> cannot confirm cause

  
  

  - Risk of individual differences as cannot randomly allocate p's to conditions due to naturally occurring IV -> IQ and navigational experience could impact volume of hippocampus instead of whether they are a taxi driver
• Nature v nurture debate

  + interactionist:

  -> how nature + nurture elements interact to cause brain plasticity

  -> enhances our understanding of how environment can alter how our innate biological factors change over time, encouraging practical applications such as using structures of the brain that you wish to exercise

  
  

  - interactionist:

  -> didn't only focus on role of innate hippocampus in humans = looked at how environment led to changes in structure of the brain
• Reductionism v holism

  Reductionism:

  ->focuses on how physiology can change + grow by comparing 2 different groups of men with different navigational experience = volume of hippocampus can pre-determine navigational experience

  
  

  Holism:

  -> innate size of hippocampal when interacted with environment/navigational experience, the volume can increase + structural plasticity can occur
• Scientific nature

  Scientific:

  -> Uses scientific equipment to allow for quantifiable measures = objective software used to analyse VBM + pixel counting

  
  

  Unscientific:

  -> Use of a correlation meaning cannot determine cause + effect between years taxi driving + volume of hippocampus as intelligence may affect this