Physiological Or Biological Approach to Psychology

Physiological or Biological Approach to Psychology

McGuire Taxi Drivers Brains

Sperry – Split Brain

Dement and Kleitman – Dreaming

McGuire Taxi Drivers Brains – how plastic are our brains? Do they structurally change with new experience? Is the Hippocampus the centre for spatial awareness and map learning?

Sperry – Split Brain – how independently does each side of the brain work? What would happen to our behaviour if our two hemispheres are split? What information and skills does each hemisphere contain?

Dement and Kleitman – Dreaming – what electrical activity is going on in our brains when we are asleep? When do we dream? How often do we dream? Why do our eyes move when we dream?

The Physiological Approach to Psychology

The assumptions of the physiological approach are that our biology has a significant impact on our behaviour. Some physiological psychologists would say that our brain and nervous system determine most of our behaviour. They study the brain, the nervous system, the endocrine system (hormones such as adrenaline, testosterone and oestrogen etc), heredity and disease, to determine their effects. In terms of the nature v nurture debate they consider nature to be most important. In the past studies have often been carried out on animals or on identical twins. However the onset of EEG machines to measure brainwaves and MRI scanning together with genetic engineering has recently extended our understanding of the human brain and how it works. The physiological approach also includes the work of evolutionary psychologists who study instinctive behaviours which are common to all animals and determine the reproduction of their species.

There are considerable strengths to the physiological approach as many tests which can be carried out such as EEG’s, MRI’s and DNA testing are highly scientific and therefore reliable. We all have very similar biological brains and nervous systems so data is also highly generalisable. However brain imaging techniques are relatively new and we cannot always be sure we are interpreting them correctly. We may see changes in brain functions but these techniques do not tell us what is causing those changes. Otherwise we often have to rely on the self report method when studying the brain and so demand characteristics may be a problem. Studies which are carried out in laboratories or hospital settings could also be said to lack ecological validity.

McGuire Taxi Drivers Brains and the Hippocampus

The Hippocampus helps us to navigate and find our way around both familiar and new environments. This part of the brain plays an important part in spatial memory and tests in laboratory animals have shown a tendency for the male species to have better spatial memories than females. This is thought to be an evolutionary difference.

London Taxi Drivers were used in the study as they undergo an intensive two year training of route and map learning of the London area before they are allowed to obtain a taxi licence. This training is known as ‘The Knowledge’.

Method: an experiment using independent groups comparing brains of taxi drivers with non taxi drivers. In addition correlational analysis was done to see if the hippocampus changes increased with time of being a taxi driver.

Subjects: 16 right handed male taxi drivers with a mean age of 44yrs. They were all healthy and had a minimum of two years experience ‘on the knowledge’. There was a control group of 50 right handed males with the same mean age range who volunteered to have an MRI scan of their brains.

Only right handed males were used as females are known to have slightly different functions in their hippocampus and whether you are left or right handed also affects how your brain is used and developed.

Structural MRI scans were used (which measure the structure rather than the function of the brains).

The Dependent variables were measured by: VBM (voxel-based morphometry) to measure the changes in shape of the grey matter. Pixel counting was also carried out on the scans of both the taxi drivers and non taxi drivers’ hippocampus to measure the volume. They sliced the scans into 26 slices looking at different sections of the hippocampus, posterior (back), anterior (front) and main body.

Control: a pixel counter was used who was highly experienced but did not know which group any of the pictures belonged so as to avoid bias.

Results:

1. The VBM analysis showed there was in increase in grey matter on bothsides at the back or posterior of the hippocampus and a decrease in grey matter at the front (anterior) of the taxi drivers. This showed that the brain is ‘plastic’ (can change shape).
2. Pixel counting showed there was no difference in the volume of the two groups hippocampus so proving the grey matter had shifted rather than expanded.
3. The correlation analysis showed change with length of time as a taxi driver in the volume of the right anterior hippocampus only.

Conclusions:

The work and learning involved in being a taxi driver in London caused structural changes to the brain. This shows that people who choose to do this kind of work do not have specifically different brains to start with but their brains develop and change with experience. It also shows that brains are plastic (can change shape with new experiences). The findings also support work carried out on animals such as monkeys and rodents as well as with patients with brain damage.

The study is important as it indicates that different parts of our hippocampus have different functions. The posterior is the part that is used when we are using previously learned information to find our way about whilst the front part is used when we are learning new layouts. This has implications for brain damaged patients and their recovery as it shows that given the right environmental stimulation some brain functions can be increased. The study also suggests that the right and left side of the hippocampus have different functions. The right side may hold more mental maps whilst the left side more memories of events.

Strengths of the study are its usefulness to the understanding of brain recovery in brain damaged patients and the ability of the brain to adapt to environmental stimulation. This supports theories of evolution which show how animals adapt over time and change their body structure and function to adapt to their changing environments.

Validity: this study does appear to be highly valid (does measure what is says it is measuring). Firstly reliable scientific techniques were used to measure the differences in brain function and secondly not only were taxi drivers compared to the control group but also correlation analysis supported the fact that as time went by the changes became more significant. The validity is also supported by the fact that the same changes have been seen in the study of rodents and other mammals.

Problems: of course learning such detailed mapping is a skill that many of us do not do and do not need. We also cannot generalise to women or even people who are left handed as there may be significant differences between these two groups. But the strengths do seem to outweigh the disadvantages on this study.

Two changes to the study and how it would affect the data:

One change I would make to the McGuire study is to use women. Other studies on mammals have shown that women do have different spatial abilities than men. However this maybe due to the fact that they have different roles in society and so have different experiences. If the same study was done one women taxi drivers it would show if the study can be generalised to both sexes or if the hippocampus changes would be different in women than men. This would be useful for the nature nurture debate as it would show if some sex differences in the brain are down to nature or simply to the experiences of the society in which women are brought up.

Another change I would make is to include left handed people. Many people are left handed. It would be interesting to see if left handed people have the same function in their hippocampus and if the same side of the hippocampus enlarges in a left handed person or if the left side of the hippocampus would enlarge rather than the right. This would enable us to know if handedness does affect brain plasticity or not and if handedness has any other effects on the brain such as spatial awareness.

Sperry – Split brain

The brain is divided into two main lobes, left and right. The left hand side of the brain controls the right hand side of the body and the right hand side of the brain controls the left hand side of the body. Most people have some lateralisation of function, that is to say one side has a different role to the other. In most people the language side of their brain is on their left whether or not they are right or left handed.

Sperry took advantage of a naturally occurring variable by experimenting on patients who had to have their corpus collosum cut in order to control severe epilepsy.

The aim of Sperry was to investigate the effects of de-connection and show scientifically the different functions of each hemisphere.

Method; A quasi experiment (as the variable was naturally occurring) in a laboratory.

Subjects: 11 patients who had already experienced a commissurotomy for their epilepsy. 9 were recent patient 2 had their surgery some years before.

Procedure: A table with a screen. The screen had a space beneath it so the patient could put their hand below the screen and touch objects on the table. The experimenter sat one side of the table and the participant the other side and objects were projected through the screen into one or other of their visual fields (either left or right).

Results:

1. Objects shown to the left visual field could not be named but could be picked up by the right hand or drawn by the right hand. Objects shown to the right visual field could be named and picked up by the left hand.

1. When shown an object in one visual field it could only be recognized again if shown to the same visual field.

1. If objects were put in the right hand they could name it but would say they would not have any awareness of it if it was put in the left hand. However they could find it by touch with the left hand if put in a bag along with other objects.

1. When subjects saw embarrassing pictures of a nude appear in their left visual hemisphere they giggled even though they could not say what they had seen. This suggests the hemisphere has its own awareness just not the speech.

1. Right hemispheres were better at carrying out mathematical problems.

Advantages and conclusions:

The study is useful in that at the time it was groundbreaking in demonstrating how each side of the hemispheres work. It also revealed the purpose of the corpus collosum in being the communication pathway between the two hemispheres. It also showed how independently the two sides of the brain can work and how each has its own purpose and function.

Validity

The problem with this study is that the patients all had severe epilepsy so it could be argued that the results are not valid to ‘normal’ brains.

Reliability:

The sample was small and we cannot repeat the experiment on people with a normal brain due to ethics

Key words:

Left and right hemisphere

Corpus Collosum

Epilepsy

Quasi experiment

Commissurotomy

Two changes to this study and how it would change the data:

This question is almost impossible to answer as we cannot objectively experiment on ‘normal’ patients as this would be unethical. When surgeons carry out brain surgery they often have the patient awake so they can talk and answer questions. By probing different parts of the brain the surgeon can then tell which part is responsible for which activity and so avoid damaging certain parts responsible for speech and movement. Brain scans which can show a brain working can now be carried out. A patient is given an injection of glucose which has a radio active tracer. They are then given tasks to do whilst their brain is scanned. The part of the brain which is being used the most uses more glucose and so the tracer shows up highlighted on the scan. This is now the best way to study brain function and would make the data more valid as we could do this on healthy patients. The only other way we could improve the study would be to make it more reliable by repeating the same experiments with more subjects to be sure that the sane results are found. I do not think this question is likely to come up.

Dement and Kleitman – Sleep and Dreams

Our bodies have different patterns or rhythms which are built into our biology. Circadian rhythms are those that happen each day based on a 24 hour cycle and all animals and plants have some kind of built in pattern of life. Plants, animals, birds respond to changes in light and temperature stimulating their sleep, migration or breeding patterns. Humans have a body clock or rhythm which determines their sleep wake cycle and also their body temperature. Our body temperature falls at night reaching its lowest point in the early hours of the morning. This is one reason why night shift workers find it so hard to sleep in the day time.

No one knows the precise reason for sleep although sleep deprivation studies have shown how brain function reduces without sleep and long term sleep deprivation can even result in paranoia and mental illness. The assumption is that sleep is required for psychological and physiological restoration. Accidents in the work place often occur at night when workers are functioning at their worst part of the circadian cycle.

Evolutionary theory suggests that we sleep to preserve resources and keep us safe in times of darkness and extreme cold however if this was true one might think that humans would have evolved to need less sleep than they do.

As well as a 24 hour cycle we also have a cycle to our sleep pattern. You need to understand this cycle and occasionally you will be asked about this cycle in an examination question:

The Sleep Cycle: the whole sleep cycle lasts for about 90 minutes

1. Stage One: we start to feel drowsy often as the light fades and the pineal gland starts to produce melatonin in the brain.
2. Stage Two: deeper stage but still can be woken easily and heart rate and breathing start to slow.
3. Stage Threedeeper sleep with more long slow delta waves on a EEG machine. Difficult to wake up, heart rate and blood pressure still dropping.
4. Stage Four delta or quiet sleep and hardest to wake up from and last in bursts of about 30 minutes.
5. Stage Five – we return to where stage one would be but instead go in REM sleep (rapid eye movement sleep). Our eyes move but our bodies cannot. We stay in this stage for 5 – 15 minutes and then go through stages two to four again and again all night.

Aim of the Dement study was to see if the REM sleep part of the cycle does correspond to dreaming and to see if the eye movements match the content of the dream. Dement also wanted to find our if subjects could tell how long they had been dreaming for.

Method: laboratory experiment in sleep lab.

Apparatus:

1. EEG machine to measure sleep brain waves
2. Electrodes attached to eyes to measure eye movements
3. A tape recorder so subjects could self report and a bell to wake the subjects

Subjects: 7 adults makes and 2 adult females. Only 5 were studied intensively the other 4 were used to confirm the findings.

Controls:

Subjects told not to have any caffeine or alcohol on days of trials

Were woken by bell so experimenter did not effect dream recall

Procedures:

1. Subjects woken at random and asked to report if dreaming
2. Subjects woken between 5 and 15 minutes when in REM sleep and asked if they could estimate length of time they had been dreaming
3. Subjects asked to explain dram and this was matched to eye movements.

Results and conclusions:

1. Most dreaming occurred in REM sleep
2. Dreams matched eye movement (when eyes went up subject said he had been climbing a ladder.
3. Subjects were very good at estimating time they had been dreaming.

1. Dement and Kleitman concluded that the measurement of REM during sleep can be used as an objective measure of dreaming and that dreaming appears to occur in real time.

The study was useful in that it was a first in scientifically measuring when we dream but it fails to tell us why we dream or indeed why we go through specific cycles of sleep. It also could be said to lack ecological validity.

Two changes to this study and how it would affect the data:

One change I would make to the study is to carry out the experiment in peoples homes. This would have an effect of making the data higher in ecological validity as we cannot be sure that sleeping in a laboratory did not affect their sleep patterns or their dreaming. However it would mean that the study was less controlled as people would not be as closely monitored in their own homes as they would be in a laboratory. This would therefore make the data less scientific. Another change that I would make to this study would be to make sure that their were an equal amount of subjects that were male and female studied as well as a range of different ages as this would make the data more generalisable. At present we cannot be sure that women are exactly the same in their dream and sleep patterns as men and the study does not tell us anything about the effect of age on sleep patterns and dreaming.