IB Psychology SL - Biological Approach Full notes
Studies:
Genetic similarities
- Polderman et al
- Bouchard et al
Neurotransmitters
- Fisher et al
- Crockett et al
Neuroplasticity
- Maguire et al
- Draganski et al
Genetics and Evolution
- Curtis et al
- Fessler et al
Local...
It is common knowledge that our conscious existence emanates from our brain. However,
neuroscience in its modern form has really only been around for 60 years. Early neuroscientists such
as Camillo Golgi, Paul Broca and Carl Wernicke relied on both animal research and dissection of
human cadavers to conduct investigations into the role of the brain in human behaviour.
Modern technology has allowed researchers to build a more accurate understanding of how the
human brain functions. Before brain imaging technology, psychologists were limited to the study of
dead or damaged brains
The sophistication with which the procedures and techniques involved in animal-based brain
research and cadaver autopsy has increased dramatically over the years. But the basic underlying
principles of a reductionist approach to understanding the functions of the brain and their impact on
behaviour are still very much relevant today. Brain-based research generally focuses on four
methodologies:
o animal research via the use of lesions
o human and animal research using post-mortem brain analysis and dissection
o brain imaging technology
o genetic analysis
Reductionist Approach
Reductionism essentially takes a complex phenomenon and boils it down to its simplest and most
primitive explanation.
The reductionist approach to research is a technique that is extremely valuable to the scientific
community. It has been argued that reductionism is the backbone of modern science, and a detailed
understanding of psychological phenomena depends on the identification of specific variables
influencing human behaviour and mental processes. The reductionistic explanation is advantageous
in that it identifies specific variables involved in the human experience of attraction, which leads to
targeted applications of the theory.
An understanding of the specific factors shaping behaviour on a cellular or molecular level is meant
to inform understanding of human behaviour and psychology as a whole. For example, the
identification of specific evolutionary factors in human mating strategies could eventually form part
of a fuller understanding of human attraction in general.
The major challenge for reductionism is that it cannot fully explain a complex system which is more
than the sum of its parts. The idea is that complex systems may develop properties that emerge
through interaction, so an understanding of the individual components of behaviour doesn't fully
explain the behaviour itself.
,PET (Positron Emission Tomography)
A type of nuclear medicine imaging that is currently the most accurate method of studying brain
activity.
PET starts with the injection of a radioactive dye mixed with glucose into the participant. The
dye produces measurable gamma rays as the sugar is metabolised in the brain. The fact that the
brain metabolises sugar is what allows the PET scan to work, as it is presumed that the more
metabolisation of glucose that occurs in a given brain region, the greater activity in that region. A
PET scan detects the rays emitted from the glucose mixture and turns them into computer images of
brain activity. The brain activity is then colour-coded by software based on the amount of glucose
metabolised in specific regions of the brain. These scans are used to examine functions, such as
blood flow, oxygen use and sugar (glucose) metabolism, to identify activity in certain regions of the
brain.
Strengths Weaknesses
- Not all brain imaging technologies can show the - Ingest radioactive substance: even though the
brain in action, as it functions, but PET scanning radioactive elements used in these scans are short
does. Therefore, PET is often used when static lived it might cause some complications - for
scans like the CT scan and MRI scan are example for pregnant women, PET scans could
inconclusive. PET scans have the advantage of hurt the baby
sensitivity of brain function over fMRI and MRI. o Although the radioactive tracer might hurt when first
injected into the body it doesn't stay radioactive for
- Able to pinpoint molecular activity in the brain, it
long, so the risk from radiation is very low.
offers the potential to identify a variety of
- Expensive compared to other forms of medical
diseases and illnesses in their earliest stages, on a
imaging.
cellular level.
- The sensitivity of this diagnostic tool is too high. In
- Useful for showing abnormalities in brain activity case a patient was suffering from chemical
levels in diseases that do not show structural imbalance for instance those who are diabetic or
changes until much later, such as Alzheimer’s just ate something before undergoing the
disease procedure, the likelihood of PET imaging false
results is high.
- Even though the radioactive components used in
the scans are not long lasting it is still exposure to
radioactive rays which is not good and which also
means there is only a number of times one can
undergo PET imaging.
MRI (Magnetic Resonance Imaging)
Produces a static image of the brain using a magnetic field and pulses of radiowave energy to make
pictures of human physiology. Uses magnetic fields to indirectly visualize brain structure
It is used to find problems such as tumours, bleeding, injury, blood vessel diseases or infection.
Physicians also use MRI to detect structural brain abnormalities in patients. MRI scans are noted for
their relatively high degree of detail (especially in comparison with older CT scans based on X-ray
technology). This is especially useful when studying the human brain at a microscopic level.
Contrast material (dye) may be injected before the MRI scan to show abnormal tissue more clearly,
but, even still, MRI scans only provide static images. People with metal clips, plates or screws in their
brains can't be scanned because of the strong magnetic field exerted by the scanner.
Strengths Weaknesses
- High resolution pictures - Only structural data
- Better than CT scans in detecting soft tissues - People with metal in the body (eg. plates/screws)
can’t be scanned because of the strong magnetic
field
- Expensive
, fMRI (Functional Magnetic Resonance Imaging)
Essentially an MRI combined with a PET scan, because it shows physiological structures in great
detail but also shows them in action as they function.
The same large magnet as in MRI is used to create images of human physiology, but fMRI also
measures changes in blood flow to different active areas of the brain, which is how activity is
measured.
When neurons in a particular region are active, more blood is sent to that region. The fMRI machine
maps changes in the brain’s metabolism (specifically, chemical changes within the cells) to show
precisely which parts of the brain are active during a wide range of human behaviours. It also
investigates the correlation between behaviour and brain activity in certain areas, and used to help
assess the effects of stroke, trauma or degenerative disease (such as Alzheimer's) on brain function.
Strengths Weaknesses
- fMRI does not require the use of radiation (like - Can not provide precise information about when a
other scans), so health risks are minimised. part of the brain becomes active
- Generally more precise than PET scans. - Expensive
- fMRI is best for research necessitating a three- - Sensitive to motion
dimensional analysis of function, as it has superior
spatial definition relative to the PET scan.
- Over the last decade it has provided new insight
to the investigation of how memories are formed,
language, pain, learning and emotion, etc.
- Good for showing WHERE activity is
Overall Pros and Cons of Brain imaging techniques
Strengths Weaknesses
- Brain imaging technologies allow psychologists to - The main issue is the sheer complexity of human
look into healthy, functioning human brains behaviour: even the most precise brain scan is
without any real fear of damage or change. unlikely to reduce any given behaviour to a single
- These technologies have made it much more neuron or molecule. Most human behaviour
possible to study the biological correlations of results from the interaction of multiple biological,
human behaviour, in the brain especially cognitive and social processes, and brain imaging
- They are much less invasive than exploratory doesn't capture this.
surgery. Scientists can use brain scan technology - Correlation ≠ causation: even if there is a
to establish broad correlational evidence between high correlation between a particular cognitive
a given behaviour and brain region. This can task and a brain pattern, we cannot be sure that
provide insight for further research or triangulate when the particular brain pattern in question is
existing research. observed, the very same correlated task must be
- They can expand knowledge about the happening. Furthermore, just because two things
relationship between biological factors and occur at the same time does not prove that one
behaviour thing causes the other.
- They can help with the early diagnosis and o Brain-based reports on behavior are neither ‘biological’
treatment of disorders like autism, Alzheimer's nor ‘psychosocial’, but instead must incorporate both
disease or schizophrenia. - Lack of ecological validity: the situation is far from
- They can help with identifying the brain area natural, so how is it possible to know if the brain
involved with problems like phantom limb pain, activity is that which would occur naturally?
therefore assisting the sufferer to overcome the - It’s expensive to use brain scan technology. 1) it
pain. reduces the total number of participants per
study as well as the likelihood of replication. 2)
not many have access, and therefore the scans
are generally carried out on people living in
wealthier parts of the world.
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