Biological Research Methods Flashcards
what are the 3 brain scanning techniques
CAT
PET
fMRI
describe the CT scanning technique
x ray computed tomography
someone lies on moving platform to be passed through scanner
dye makes picture clearer for analysis
used to check damage of brain
knowing how areas block the x ray shoes something about areas (eg is a tumour present or damage)
what evidence is there to support CAT studies
Betts (2009)
Case of Herbert Weinstein
his defence used CAT scanning to show he had damage to the brain that might have led his aggression (strangling his wife)
this persuaded the jury that his actions were not thought through
Betts suggested that 10% of people pleading NGRI have a psychosis that is neurologically based
strengths of CT
- less harmful than PET scans
- can detect changes in physical structure
- can be used in industry (wide application)
- not painful and non-evasive
weaknesses of CAT scans
- MRI gives clearer picture when it comes to examining causes of headaches so fits more in needs of psychology
- xrays can cause damage - notably cancer (radiation from scan is what is normally exposed to in the course of a year)
describe PET scans
positron emission spectroscopy
picks up ‘hot spots’ in the brain enabling us to find out which parts are working at a particular time
radioactive tracer is added to chemical (usually glucose) and injected into vein in arm
tracer provides positrons which give signals that are recorded
as glucose is used in brain, it shows up as an area of activity
used to study blood flow in brain, check stroke damage, or nervous system problems
what are positrons
small positively charged particles
what evidence supports PET scans
Raine et al (1997)
investigates idea that brains of murderers are different to that of non murderers
he used those accused of murder but pleaded NGRI
he used PET scans to give images of participants brains and then certain areas linked with aggression
give the strengths of PET scans
- less dangerous and distressing than surgery
- validity (construct)
- reliable as it can be repeated eg whenever someone speaks the same area of the brain is used (sane areas of brain are consistently found for different activities so reliable)
give the weaknesses of PET scans
- radioactive tracer is invasive
- head in tube can be claustrophobic
- difficult to isolate different brain functioning specifically
describe fMRI scanning
functional MRI scanning
blood and oxygen levels are measured / picks up on changes of use of brain areas depending on task being carried out
relies on fact that blood flow and neuronal activity are linked
good for finding out how brain functions by using ‘normal patients’
what evidence is there to support fMRI scans
Brunnlieb et al (2013)
investigated if taking vasopressin would moderate aggression
(studies already suggested it worked in rats)
used healthy adults who took it nasally
one group had placebo other had real
double blind technique
test used fMRI to see activity in brain
participants had to make a decision about punishment
no differences found between real and placebo - study didn’t work
give the strengths of fMRI scans
- no danger from radiation or invasion
- detection in changes of blood are very precise so brain areas in use are identified clearly
give the weaknesses of fMRI scans
- cannot look at actual receptors or neurotransmitters whereas a PET scan
- too much head movement can distort imaging
- brain is never at rest so hard to get a baseline measure
- risks eg those with pacemakers, claustrophobia
give the strengths of twin studies
- both MZ and DZ twin babies are born at same time and share similar environment
- MZ twins have identical genetics so used to investigate the influence of genes on behaviour
- both MZ and DZ share environment
give the weaknesses of twin studies
- MZ twins will be treated more alike than DZ twins so environments are more similar
- MZ twins do not share environment even in womb so tend to develop differently despite DNA being the same
- epigenetic modification as some genetic characteristics are triggered by the environment
- no study has found any behavioural characteristics that is 100% shared by MZ twins so genetics are bound to play a part
what is the contemporary study for twin studies
Brendgen et al 2005
what were the 3 key aims of Brendgen study
- to see if social aggression could be caused by genes or the environment
- to see if social aggression shared the same cause as physical aggression
- to see if one type of aggression leads to another type
who were the sample of Brengen’s study
6 year old twins from Quebec, Canada
234 pairs of twins - 94 MZ twins (44 males, 50 males), 140 DZ twins (41 males, 32 females, 67 mixed)
how were the teacher ratings and the peer ratings done
teacher: based on agreement with a number of statements on physical and social aggression taken from preschool behaviour scale and direction and indirect aggression scale
3 point scale
examples “to what extent does your child try to make others dislike a child” (social) “to what extent does the child get into fights” (physical)
peer ratings: each child in twins’ class given booklet containing photos of every child in class and asked to circle 3 pics of children they thought matched behaviour descriptions
eg: “tell others not to play with a child” or “gets into fights”
what were the results of Brendgens study
- physical aggression heavily influenced by genetics
- social aggression influenced by environment
- physical aggression layer led to social aggression but not other way around
- higher concordance rates for physical aggression in MZ twins than DZ
- similar concordance rates for social aggression between MZ and DZ
what was the conclusion of Brengen’s study
- strong genetic component to physical aggression but not social aggression
- social aggression likely to be due to environment
- as children grow they tend to become more socially aggressive because of social conventions on physical violence and developing different ways to express themselves
give the strengths of adoption studies
- best way of separating genes from environment so the two can be tested
- ## studies are longitudinal and so developmental trends can be identified from them
give the weaknesses of adoption studies
- environment of adoptive families is not as different from biological families
- only certain types of family are accepted as adopters of children
