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G542: Core studies
MAGUIRE ET AL.
Section A
1a)
The IV is whether the participants were London taxi drivers or not, the DV was the size of the
hippocampus.
b)
One effect was that the VBM showed that the taxi drivers had significantly increased grey
matter in the right and left hippocampi compared with the controls.
2a)
One limitation in this study of the independent measures design is that the two groups may
have had pre-existing differences in the hippocampi which were not caused by the taxidriving experience.
b)
The IV could not be manipulated because the participants were already either taxi drivers or
not; they could not be allocated to the groups by Maguire.
3a)
The sample were right-handed London taxi drivers who had been licensed for more than 1.5
years.
b)
One limitation of this sample is that they all had the same type of experience of spatial
memory and navigation. They would have been more representative of the general public if
they had had a variety of different jobs such as bus drivers and pilots.
4a)
One technique was voxel-based morphometry, which identifies differences in the density of
grey matter in different parts of the brain. Grey matter is associated with higher-order
thinking. The other technique was pixel-counting which involves counting the single points
on a graphic image of a slice of the brain.
b)
One difference between the MRI scans of the two groups was that the taxi drivers showed
increased grey matter in the posterior hippocampi, while in the controls there was relatively
more grey matter in the anterior hippocampi.
5a)
These groups were used because the aim was to find out about the role of the hippocampus
in spatial memory and navigation, and taxi drivers have absorbed a large amount of spatial
information over a short period when they learn ‘The Knowledge’. The non-taxi drivers were
used as a comparison group or control who have not had this experience.
b)
Two criteria were that they were right-handed and had been licensed more than 1.5 years.
6a)
The study suggests that there is a relationship between navigational skills and the relative
distribution of grey matter in the hippocampus; this indicates that the hippocampus has the
role of storing memories of people and events, and with integrating information into an
existing map.
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b)
One finding that supports this is that the taxi drivers had significantly increased grey matter
in the right and left posterior hippocampi compared to controls.
7a)
Two controls used in this study were that the taxi drivers all had healthy medical,
neurological and psychiatric profiles, and that they had all been licensed over 1.5 years.
b)
It was important to use controls because these minimised the likelihood that other factors
had influenced the results, for example if they had various medical conditions this may have
affected their hippocampus structure. Also, the fact that they had all been licensed over 1.5
years meant that any effect on their brain structure would have had an equal chance to take
effect.
8a)
One method used to measure the size of the hippocampus was pixel-counting which
involves counting the single points on a graphic image of a slice of the brain.
b)
One problem is that although it gives a clear picture of current size, it is a snapshot only and
cannot give an indication of what the size was previously or exactly how the changes occur.
9.
One piece of evidence that supports the role of the hippocampus in spatial memory is that
the increased navigational skill of the taxi drivers was accompanied by a relative
redistribution of grey matter in the hippocampus, indicating that that structure was involved
in the dealing with the new knowledge they have learned.
10a)
The MRI scans created images of the whole brain, which were then used to measure the
size and volume of the participants’ hippocampi.
b)
One piece of evidence that the brains of taxi drivers are different from the brains of the
controls is that the taxi drivers showed increased grey matter in the posterior hippocampi,
while in the controls there was relatively more grey matter in the anterior hippocampi.
11a)
A negative correlation is where one variable increases while the other decreases; in this
study increased time spent as a taxi driver was correlated with less volume in the anterior
hippocampus.
b)
One conclusion is that spending time as a taxi driver results in a redistribution of grey matter
in the hippocampus from anterior to posterior.
12a)
That as time as a taxi driver increased, so did the amount of grey matter in the right
posterior hippocampus.
b)
One limitation is that correlations do not show cause and effect, meaning that this finding
cannot be taken to indicate that the taxi driving time caused the increase in the grey matter
in the hippocampus – other variables may have been involved.
13a)
Pixel counting involves producing MRI scans of photographic slices through the participants’
brains, each 1.5mm thick, and then counting the single points on the image to discover the
size of the brain structure (hippocampus).
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13b)
One reason this is reliable is that this is a scientific, objective, quantitative method with a
standardised procedure which should produce the same results if carried out by another
observer; a second person would count the same number of pixels in the same image.
14.
One group was 16 right-handed male London taxi drivers with a mean age of 44 years and
who had held their license for at least 1.5 years. The other group was a control group of 16
men with the same mean age as the experimental group.
15a)
Two criteria were that they were right-handed and had been licensed more than 1.5 years.
b)
One difference in hippocampal size between the two groups was that the taxi drivers had
significantly increased grey matter in the right and left hippocampi.
16a)
VBM enables every point of the brain to be examined in an objective way, and identifies
differences in the density of grey matter. By registering every brain to a template, this gets
rid of most of the large differences in brain anatomy between people, and then the
technique compares brains at every voxel.
b)
This template was produced by normalising images of brains and creating an ‘average’
image with which to compare the participants’.
17a)
No difference was found in the total hippocampal volume because the taxi-driving
experience created a redistribution of grey matter rather than creating or destroying existing
material.
b)
The data in this study may not be valid because although the hippocampal volume
increased in the posterior hippocampus for the taxi drivers, this does not necessarily mean
that it is the only part of the brain responsible for spatial memory.
18a)
The sample may be representative because there was a wide age range included (32–62)
so the findings would be generalisable of people of most working ages.
b)
It is unrepresentative because it only included males, so the findings are not generalisable
to female taxi drivers, particularly as anecdotally women have different spatial abilities from
men.
19a)
The control group consisted of 16 age-matched males.
b)
It is necessary to have a control group as a comparison for the experimental group: to see
whether any effects found in the taxi drivers’ brains would also apply to the non-taxi drivers.
20a)
The conclusion regarding spatial memory is that the hippocampus is involved in this
function, and that the left hippocampus has a different role from the right. The left seems to
store memories of people and events while the right integrates information into an existing
map.
Section B
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1.
Research has shown that the hippocampus is central to spatial memory. For example, in
species that have a need for spatial memory the hippocampi are larger than in species with
less need for spatial memory (when overall brain and body size are taken into account). In
some animals the size of the hippocampi (hippocampal volume) increases during seasons
when they use their spatial memory most.
2.
The aim of the study was to demonstrate that the hippocampus is the region of the human
brain associated with spatial memory and navigation.
3.
One hypothesis was that taxi drivers would show larger hippocampi than non-taxi drivers due
to their increased navigational experience and knowledge.
4.
This is a natural experiment (or quasi-experiment). It is an experiment because there is an IV
with different conditions (taxi driver/non-taxi driver) and a DV (size of the hippocampus). It is
a natural experiment because these conditions are not directly manipulated by the
researcher; the two groups already existed because the participants were either taxi drivers
or not already.
5.
One strength of this is that it is the only realistic way of comparing people who have not got
a huge amount of spatial knowledge and navigational experience with those who have. The
fact that it is an experiment with an IV means that cause and effect can be inferred, in this
study that the navigational experience of the taxi drivers has affected the size of the
hippocampus.
6.
One weakness is that because this is a quasi-experiment, individual differences may have
affected the participants’ pre-existing spatial abilities and navigational experience as well as
just having undertaken ‘The Knowledge’.
7.
16 London taxi drivers with a mean age of 44, who were all licensed for more than 1.5
years, male and right-handed.
8.
Two different samples were used to allow for a comparison of the brain scans (specifically
the hippocampi) of the taxi drivers who had a huge experience of navigating with those of
other participants who had not (the control group).
9.
The sample was selected by opportunity sampling, to be all male and to have had a license
for more than 1.5 years.
10.
One strength of the sample was that as they were all similar in terms of being licensed for
some time and being male, this should allow the experimenters to draw conclusions when
comparing with the control group as many extraneous variables were controlled.
11.
One weakness is that they may well have had similar intelligence levels in general and
perhaps been similar in other ways which may also have affected their scans.
12.
This is a snapshot study because it takes just one set of data for each experiment, and
captures the participants’ behaviour at one moment in time. It does not take account of
development over time. In this study, it shows people’s hippocampal size at a particular
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point in time rather than emphasising the changes over time as they learned more about
London navigation.
13.
One strength of snapshot studies is that they are quick to carry out, so Maguire could gain
all her data at once. This allowed her to draw rapid conclusions about the effect of
navigational experience on brain structures and their relative size.
14.
Snapshot studies do not allow the researcher to discover whether results are due to the
development of the behaviour or to individual differences. In the Maguire study the
participants will have had different experiences and differing innate abilities for navigation
and spatial awareness. Therefore their hippocampi may have been affected by other factors
than simply being a taxi driver or doing ‘The Knowledge’.
15.
One ethical issue raised by this study is that exposing people to MRI scanning when it is not
necessary for medical reasons could be considered to be invasive and potentially upsetting.
Secondly, if the brain scans had revealed health issues there would have been an ethical
issue for the researchers in deciding what to do with that information.
16.
The experimental group and the control group had structural MRI scans which were then
analysed using voxel-based morphometry and pixel-counting. In the VBM, differences in
density of grey matter in different parts of the brain were analysed. In the pixel-counting
procedure, hippocampal volume was calculated using a counting method of single points on
the MRI scan images. 26 ‘slices’ of the brain were analysed by experienced analysts who did
not know whether the scan they were looking at was a taxi driver or not. Total hippocampal
volume was calculated by adding up the pixels from each slice and multiplying this by the
distance between the adjacent slices. A correction was then made to account for the fact
that some people would have larger brains than others.
17.
One change in this study could be to have women participants. These would be in both the
taxi driver sample and the control sample. As in the original study, they would be matched
for age.
Another change to this study would be to recruit a sample of left-handed taxi drivers and
controls. In the same way, they would be matched for age, etc.
18.
It is difficult to say whether the first change would alter the results. Often, people claim (and
some research has backed this up) that women are less good at navigation and mental
maps than men and it is possible that conducting MRIs in this way may discover that the
female taxi drivers do not have such a markedly different posterior hippocampal volume as
the male taxi drivers; and that this might bring down the overall significance of the results.
However, it might also be possible that female brains have slightly different areas of
specialism and it might be that a different part of the brain shows changes according to
years of taxi driving. Certainly, this would be an interesting change to the study and would
tell us about female brains and navigation, which the original study does not.
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It would be interesting to see what effect left-handed participants had on the results.
Instead of finding that it was the right anterior hippocampus which was larger in the controls
than in the taxi drivers, the picture might be reversed – that it was the left and so on.
19.
Quantitative data in this study included the area measurements of the cross-section of the
three regions of the hippocampi in mm squared, and the amount of grey matter in the
posterior hippocampi.
20.
One strength of quantitative data in this study is that it allows easy analysis and
comparison, providing a numerical conclusion for whether navigational experience does
create differences in the size of the hippocampi. The scans and the VBM and pixel-counting
methods create clear, objective data so the taxi drivers could be directly compared against
the non-taxi drivers.
21.
One weakness of quantitative data is that it does not provide insight or detail into how
exactly the changes had occurred, or how the participants’ subjective experiences related to
the differences shown by the scans.
22.
There was significantly more grey matter in both left and right hippocampi (LH and RH) of
taxi drivers than controls. This difference was only in the posterior portion of both RH and
LH. In contrast, the controls had relatively more grey matter in the anterior RH and LH. In the
control group the anterior RH and the body of the RH were larger (i.e. had more volume)
than taxi drivers. In the taxi drivers both the posterior RH and LH had greater volume than in
the controls. There was a positive correlation between time spent taxi-driving and volume of
the posterior RH.
23.
VBM and the pixel-counting techniques are very reliable as they are based on scientific
methods which should not be open to interpretation or experimenter bias. This was
reinforced by the fact that the analyst was ‘blind’ as to which group the brain scans came
from, meaning that they would not have interpreted them in a way which conformed to their
expectations. Therefore another neutral analyst should obtain consistent results by
reproducing the method. The fact that the participants did not actually have to do anything
(except be scanned) reduces the scope for participant biases, again making it more likely
that the findings would be consistent as the research was not dependent on measuring
behaviours or thought processes. The standardised procedure would make the study
replicable.
24.
The scientific method used is a valid way of measuring hippocampal volume and density of
grey matter because it is a direct measurement of a physical attribute. This in turn appears
to be a valid way of measuring spatial memory and navigation as other research has shown
that the hippocampus is the key region of the brain responsible for this ability. However, we
might be able to infer that taxi driving might increase posterior hippocampal volume (though
see critical comments above), but it may not be valid to infer that other forms of navigation
(e.g. navigating a boat, or even just on foot, or creating a mental map of a rural area rather
than an urban area) would have the same effect on structures of the brain. Without studying
people with such skills, it would be impossible to be sure.
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25.
The data collection method lacks ecological validity in this study as scanning the brain is an
unusual way of investigating brain processes that is far from an everyday occurrence for the
participant. However, it could be argued that this method is very appropriate for
physiological psychology where the brain structures are seen as of paramount importance,
and indeed it is the only practicable method for discovering whether there is a basis for
ideas about neuroplasticity in relation to experiences and knowledge.
Section C
1.
One assumption of the biological approach in psychology is that much of human behaviour
is governed and can be explained by biology, e.g. hormones, genes, neurotransmitters, brain
structure and so on. This means we probably have less control and free will than we would
like to think.
2.
The physiological approach could explain individual differences in memory by arguing that
particular structures in the brain are related to specific cognitive functions, and that the size
of these may be related to people’s particular skills. In Maguire’s study, evidence suggests
that the hippocampus plays a special role in memory related to navigational tasks. The
physiological approach would also suggest that a great deal of use of a particular cognitive
function such as memory could cause structural changes in the brain.
3.
One similarity with Dement and Kleitman is that both studies monitor the brain. Maguire et
al. use an MRI scan, while Dement and Kleitman use an EEG. Both studies use these
techniques because both are interested in the relationship of the brain with psychological
phenomena – Dement and Kleitman are interested in linking the biological event or REM
with the psychological event of dreaming; Maguire et al. are interested in linking the
biological structure of the brain (size of hippocampus) with the psychological activity of
navigation.
One difference between the two studies is that Dement and Kleitman’s study is monitoring
on-going, ‘live’ changes in brain activity. The EEG shows differing levels of activity in the
brain as it is really happening, second by second, (akin to ‘live TV’). In contrast, the MRI just
shows a one-off image of the brain, fixed at a particular point in time (akin to a photograph).
4.
One strength of the biological approach is that it is scientific. It probably represents the most
scientific end of psychology. This means that it is objective, usually empirically based and
widely respected. For example, in Maguire, the procedures use advanced technological
processes and equipment and the procedures were highly controlled – same VBM and pixelcounting techniques, single blind technique so observers did not know whose scans they
were analysing and so on. Because all these aspects of the procedure increase the validity
and objectivity of the research, it is widely accepted and respected.
Another strength of the biological approach is that it generally produces useful contributions
to psychology – both in terms of applications and in terms of usefulness for helping further
research in the area. For example, Maguire’s work is useful in considering how, because the
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brain has plasticity (it can alter and re-form itself as a function of environment and
experience) this gives hope to sufferers of brain damage. This study suggests that brain
functions which may have been lost after brain injury or stroke can return with sufficient
practice and exposure. This is very valuable to know because it can mean that such people
should not just be ‘written off’ but instead deserve an intensive, well designed programme
of rehabilitation.
One weakness of the biological approach is that it can be reductionist – only looking at
simple explanations. For example, in Maguire, she focuses purely on navigational
experience and knowledge as causes of the differences found in the hippocampi of the two
groups, when actually the situation may be more complex than this and other factors may
have come into play as well, such as genes.
Another weakness of the physiological approach is that its methods tend to lack ecological
validity. For example, Maguire relies on technology to investigate brain structure but it may
be more useful to look at people’s performances on everyday tasks and how they feel about
their abilities or lack of them in order to gain full insight into the effects of navigational
experience.
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DEMENT AND KLEITMAN
Section A
1a)
The IV is whether the participants were woken from REM sleep or non-REM sleep, and the
DV was the recall of dreams.
b)
One way the DV was measured was by waking the participants in various stages of sleep
and asking them to report into a tape-recorder what they had been dreaming about.
2a)
Caffeine and alcohol.
b)
One problem with asking participants not to take these substances is that they might do so
usually, so their sleep in the study would be different from their normal sleep.
3a)
An EEG measures electrical activity in the brain and measures changes in voltage.
b)
One limitation of using an EEG is that although it can reveal what stage of sleep the
participant is in, it cannot tell whether or not they are dreaming or the content of dreams.
4a)
It measures movements of the eyeballs.
b)
One limitation is that, although it can reveal whether the participant is in REM sleep or not, it
cannot tell whether they are dreaming or what the content of the dream is.
5a)
Two controls were that all participants were told not to have caffeine or alcohol before the
study, and they were all woken by a bell on their bedside.
b)
The caffeine and alcohol control was used so that these substances would not affect the
nature of the sleep the participant experienced, or the frequency or content of any dreams
they had, influencing the results separately from the stage of sleep.
6a)
Controlled observations were made by waking the five intensively studied participants at
various intervals to avoid unintentional patterns, for example by using a random number
generator. Participants were woken by a bell at their bedside and asked to speak into a
recording machine to say whether they had been dreaming and if so, what about.
b)
One strength of this method is that neither participants nor experimenters had conscious
control over when the awakenings took place, so their expectations about dreaming could
not influence the results.
7a)
Two characteristics of REM sleep are that rapid eye movements occur, and the brain wave
pattern is similar to a waking pattern.
b)
It is not possible to manipulate the IV because the stage of sleep the participant was in
could not be affected or selected by the researcher.
8.
Evidence supporting the link between REM and dreaming includes that there was a high
incidence of recall of dreams during REM periods and a low incidence of recall during non-
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REM periods; and that the length of REM activity was proportional to the estimated duration
of a dream.
9a)
One way in which the sample is representative is that it is likely that these participants’
sleep patterns are similar to everyone else’s; there is no reason to believe that they had
atypical experiences of sleep and most people’s sleep patterns follow a ‘normal’ sequence.
b)
One way in which the sample is unrepresentative is that there was a gender imbalance
which does not reflect the general population (7 men and 2 women).
10a)
The procedure was standardized by ensuring that all participants were asked to refrain from
consuming alcohol and caffeine prior to the study; and that they all slept in the same
laboratory conditions.
b)
This standardization is important because otherwise confounding variables could affect the
outcome of the study, for example if some participants took alcohol and caffeine these
could affect the dreams they had regardless of whether they were in REM sleep or not.
Standardisation ensures that all participants have the same experiences while in the study.
11.
One piece of evidence that supports the link between REM and dreaming is that there was a
high incidence of dream recall from REM periods and a low incidence of dream recall from
non-REM periods. One piece of evidence that challenges this link is that sometimes dreams
were recalled even when the participants had not been woken in REM sleep.
12a)
Two characteristics of the sample were that there were 9 of them and they were all adults.
b)
This may have affected the findings because the small number may have meant that they
had atypical experiences or sleep patterns, and the fact that they were adults means that no
evidence has been provided for less-developed brains and whether REM has the same
characteristics for children.
13a)
This study lacked ecological validity because normally people would not sleep in laboratory
conditions attached to electronic equipment.
b)
It was appropriate that it lacked ecological validity because use of the EEG and EOG was the
only to gather the relevant scientific quantitative data necessary for valid findings.
14a)
One hypothesis was that there would be a relationship between eye movement periods and
dream recall.
b)
Results relating to this hypothesis were that there was a high incidence of recall of dreaming
during REM periods and a low incidence of dream recall during non-REM periods.
15a)
Data was collected by asking the participants to say, if they had been dreaming when they
were awakened, whether their dream had lasted for 5 or 15 minutes.
b)
Participants were 82% correct in their estimates of whether their dreams had lasted 5 or 15
minutes, as measured against their periods of REM.
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16a)
One piece of evidence that dreaming in non-REM was ‘leftovers’ from REM periods was that
any dreaming reported by people awoken from non-REM sleep was when they were within 8
minutes of having finished a period of REM.
b)
One other characteristic of REM is that the muscles show a lack of tone.
17a)
A positive correlation is one where, as one variable goes up, so does the other.
b)
One problem with assuming that REM sleep is the same as dreaming is that we cannot be
completely certain that dreaming does not occur at other times.
18a)
One example of a dream where eye movements had been mostly vertical was when the
participant dreamt of standing at the bottom of a cliff and looking at climbers at various
levels.
b)
One example of a dream where eye movements had been mostly horizontal was when the
participant dreamt of people throwing tomatoes at each other.
19a)
One reason why this data may not be reliable is that the sample size was so small that other
people as participants may have produced different results; for example, these participants
may have had particularly vivid dreams.
b)
One reason why this data may not be valid is that the participants may have invented the
dreams they reported as they may have felt obliged to report a dream even if they were not
really having a dream at the time.
20a)
This is an experiment because there was an IV (whether the participant was woken from
REM sleep or non-REM sleep) and a DV (reports of dreaming and dream length).
b)
This is a laboratory experiment because the participants were studied while they slept in a
controlled environment specific to the research, containing technical equipment such as the
EEG.
Section B
1.
Different stages of sleep have been identified by previous research. One way to classify the
stages is on the basis of eye movements. At certain times during the night a person’s eyes
dart about under closed eyelids. This is called rapid eye movement sleep or REM sleep. This
stage is also associated with a unique brain wave pattern – fast, desynchronised electrical
activity in the brain that resembles the state of the awake brain. Research has found that
people in REM sleep are likely to be dreaming, so this might provide a very useful way of
knowing when someone is dreaming and would permit the objective study of dreams.
2.
The aim of the study was to investigate the link between eye movements and dreaming to
demonstrate that dream experiences and REM activity are connected.
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3.
One hypothesis was that there would be a high incidence of dream recall during REM
periods and low incidence during NREM periods.
4.
This can be considered to be a natural experiment (or quasi-experiment). It is an experiment
because there is an IV with different conditions (whether woken in REM or NREM) and a DV
(dream recall). It is a natural experiment because these conditions are not directly
manipulated by the researcher but occur naturally – the experimenter cannot dictate which
stage of sleep the participant is in.
5.
One strength of this is that it is the only way of studying sleep as no one can influence the
stage of sleep someone is in. The fact that it is an experiment with an IV (woken in REM or
NREM) means that cause and effect can be inferred, in this study that the stage of sleep
affects dream recall.
6.
One weakness is that because this is a quasi-experiment, individual differences may have
affected the participants’ ability to recall dreams.
7.
Nine adults, seven males and two females, five of whom were studied intensively.
8.
The sample was selected by opportunity sampling, meaning that they were people easily
available to Dement and Kleitman for a sleep study.
9.
One strength of the sample is that is that it could be argued that because sleep is a natural
phenomenon common to all humans, these individuals would be likely to be representative
of the rest of the population because their experiences of sleep stages and dreaming would
be the same as everyone else’s.
10.
One weakness is that this is a very small sample (only five participants were studied
intensively); this means that the data gathered from them about their ability to recall dreams
from various stages of sleep may not be consistent with the data from another sample.
11.
One ethical issue is that the experience of having disrupted sleep, and trying to sleep in a
laboratory attached to equipment may have caused them to feel anxious and stressed.
Another is that being woken at irregular intervals through the night may have caused them
persistent sleep problems which could have continued into the future.
12.
Participants were asked to come to the lab just before their usual bedtime, having abstained
from coffee or alcohol on the day of the study. Electrodes were attached around their eyes
to measure electrical activity and therefore eye movement, and to their scalp to measure
brain waves via EEG. The participants went to sleep in a darkened room. At various times in
the night participants were woken by a bell by their bed. They were awoken to a random
pattern either during REM or during other sleep stages. They were woken on average 5.7
times per night. They had to say into the tape recorder if they had been dreaming or not,
and if so how long they had been dreaming for and what about. The participant could then
go back to sleep.
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13.
One change to the study is that it could be conducted on a larger sample of participants.
Instead of just nine participants, they could widen it to, e.g. 20 or even 50 participants and
study each participant for two or three nights.
Another change to the study could be that they conduct it in the participant’s home instead
of in a laboratory.
14.
In terms of the overall results, they would probably find that there was still a strong
relationship between REM and dreaming. However, they might uncover more individual
differences in terms of the pattern of the different stages of the sleep stages, duration of
REM, and ability to recall a dream. However, having a larger (and therefore, likely to be more
representative) sample should mean that the results can more validly be applied to the
general population.
This should mean that the participant should sleep more naturally as they would be in their
own bed and normal sleeping environment (normal smells, bed linen, background noise and
so on). Overall, this might change the pattern of sleep and depth of sleep – people might
sleep more deeply if they are more relaxed at home), but it probably would not affect the
overall finding that there is a relationship between REM and dreaming.
15.
Qualitative data was gathered by waking participants with a door bell, to various patterns,
and asking them to recount into a tape recorder the dreams they were having when they
were woken, if any.
16.
Two examples of qualitative data were descriptions of the dreams participants were having,
and descriptions of the participants’ reactions when woken, such as that they were
bewildered.
17.
A strength of qualitative data is that it provided detailed information about the content of
the participants’ dreams, which could not be described numerically. This allowed Dement
and Kleitman to assess whether the content tallied with the visible movements of the eyes.
18.
One weakness is that the qualitative data is difficult to analyse and to represent in a concise
clear fashion; themes are hard to draw out and Dement and Kleitman are left with only one
example to back up their theory in the case of horizontal eye movements, for example.
19.
Quantitative data includes how many dreams were recalled after being woken in REM and
NREM, and the number of times the participants were right in their estimate of dream
length.
20.
One strength of quantitative data in this study is that it allows easy analysis and
comparison, for example to see exactly how many times as a percentage the participants
could remember their dreams while woken in REM compared with NREM.
21.
One weakness of quantitative data is that it does not provide insight into how the
participants felt about their dreams and does not build up a detailed picture of sleep and
dreaming experiences.
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22.
On average REM activity lasted 20 minutes and occurred every 92 minutes. The frequency
was characteristic for each individual. Episodes tended to be longer later on in the night.
Participants frequently reported having a dream when woken during REM sleep (65–90% of
the time) but were less likely to report a dream in NREM sleep (3–12.5%). Most of recall in
NREM periods was within eight minutes of the end of an REM episode. Participants were
83% correct in estimating whether REM activity lasted for 5 or 15 minutes. There were
significantly more correct estimates of length of REM than incorrect estimates (92 correct,
19 incorrect). There was a significant positive correlation between the duration of REM
activity and the number of words used to describe a dream. There was a strong association
between pattern of REMs and the content of dreams. For example horizontal eye
movements during REM sleep were linked in one participant to a dream about two people
throwing tomatoes.
23.
Dement and Kleitman addressed reliability by double-checking the results from their main
five participants with four others, which would improve the likelihood of consistency. The
use of EEG and EOG, in common with other scientific, technology-based procedures, lend
themselves to easy, reliable replication. The standardised procedure and lab environment
means that the study could be easily repeated although the small sample size may mean
that results would be different from another group of people.
24.
The use of the EEG and the EOG, which are scientific and objective measures, means that
the measurement of the stage of sleep is valid. However, the self-report nature of the data
collection means that participants may have invented the dream content, and even whether
they were dreaming or not, due to demand characteristics, so this may not give a valid
picture of their dream experiences.
25.
There are many ways in which the sleep that was studied wasn’t very much like normal
(repeated wakings, strange bed, less sleep than normal, etc.) so it is necessary to be
cautious about making generalisations from these findings. However, even if dreaming was
affected (such as there being more or less dreaming) the contrived nature of the study might
not affect the fact that when you do have REM activity you are dreaming, so the results may
be relevant to everyday life.
Section C
1.
One assumption of the biological approach in psychology is that much of human behaviour
is governed and can be explained by biology, e.g. hormones, genes, neurotransmitters, brain
structure and so on. This means we probably have less control and free will than we would
like to think.
2.
The physiological approach could explain dreaming by focusing on the different stages of
sleep and the brain wave patterns of each. REM sleep seems to be linked with dreaming,
and REM sleep is governed by physiological processes associated with electrical activity in
the brain.
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3.
One similarity with Maguire et al. is that both studies monitor the brain. Maguire et al. use
an MRI scan, while Dement and Kleitman use an EEG. Both studies use these techniques
because both are interested in the relationship of the brain with psychological phenomena –
Dement and Kleitman are interested in linking the biological event or REM with the
psychological event of dreaming; Maguire et al. are interested in linking the biological
structure of the brain (size of hippocampus) with the psychological activity of navigation.
One difference between the two studies is that Dement and Kleitman’s study is monitoring
ongoing, ‘live’ changes in brain activity. The EEG shows differing levels of activity in the brain
as it is really happening, second by second, (akin to ‘live TV’). In contrast, the MRI scans
used in Maguire et al. just show a one-off image of the brain, fixed at a particular point in
time (akin to a photograph).
4.
One strength of the biological approach is that it is scientific. It probably represents the most
scientific end of psychology. This means that it is objective, usually empirically based and
widely respected. For example, in Dement and Kleitman the use of the EEG and EOG is
scientific and objective. Because all these aspects of the procedure increase the validity and
objectivity of the research, it is widely accepted and respected.
Another strength of the biological approach is that it generally produces useful contributions
to psychology – both in terms of applications and in terms of usefulness for helping further
research in the area. For example, Kleitman’s work on the physiological/biological aspects
of sleep and dreaming means that he is often described as ‘the father of modern sleep
research’ – linking REM and dreaming has meant that the research provided a tool (both for
other research and for diagnosing people with sleep disorders) for investigating sleep. This
really has changed the way that we think about sleep, work with sleep disorders, and how
sleep is researched.
One weakness of the biological approach is that it can be reductionist – only looking at
simple explanations. For example, in Dement and Kleitman, they are not interested in the
psychological motivations for particular dreams, why people dream particular things and
what they might mean. So, whereas Freud would be interested in interpreting the content of
the dream in terms of fears and wishes, the biological approach completely ignores this.
Therefore, it could be said that it is reductionist as it only looks at the simple explanations
and ignores more complex psychological explanations. Dreaming is probably a fusion of
physiological activity and ‘subconscious’ activity.
Another weakness of the physiological approach is that it overlooks nurture and overemphasises nature. For example, the implication of Dement and Kleitman’s study is that
dreaming is hard-wired into humans as a result of the genetically determined physiological
activity of REM and sleep stages.
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SPERRY
Section A
1a)
Hemisphere deconnection is when the two halves of the brain (hemispheres) are separated
by severing the corpus callosum which carries communication between them.
b)
Hemisphere deconnection affected the participants when they were shown stimuli to one
visual field in that if they were shown an object in their left visual field, which is processed by
the right hemisphere, they could not describe the object as the right hemisphere has
minimal language capacity.
2.
One method used to assess the split-brain patients was to show a $ sign to the left visual
field at the same time as showing a ? sign to the right visual field, to see which symbol could
be described or recognized subsequently. Another was to place two objects simultaneously
in the hands of the participants, which were then hidden in a pile of other objects, to see
whether each hand would identify only the item it had previously held or both items.
3a)
One difference between ‘split-brain’ patients’ and ‘normal’ people’s ability to identify objects
by touch was that although the latter could name items held in both hands, ‘split-brain’
patients could name an object that was held in the right hand but only guess about items
held in the left hand.
b)
This is because the right hand is processed by the left hemisphere, which contains language
capabilities. The left hand is dealt with by the right hemisphere which has virtually no
language. In the ‘normal’ patients, the information from both hands can pass across the
corpus callosum and be received by both hemispheres equally.
4.
Visual stimuli were presented to the participants flashing them very briefly (0.1 sec) onto the
left or right visual field via a screen, while the participant gazes at the centre of the screen
and has one eye covered.
5.
One finding is that if a composite word such as KEYCASE is flashed partly to the right
hemisphere and partly to the left, the participant will be able to spell the word ‘case’ with his
right hand (RVF goes to left hemisphere which has language and controls the right hand) but
say select a key from objects with the left hand (LVF goes to right hemisphere which controls
the left hand). Another is that if two objects are placed simultaneously one in each hand and
then hidden in a pile of objects, each hand will select their own object but ignore the other.
6a)
The deconnection was done to alleviate epileptic seizures by limiting the spread of the
electrical activity in the brain.
b)
If an object was placed out of sight in their left hand, the participant cannot name it.
7a)
Visual material presented to the RVF could be described in speech because it is processed
by the left hemisphere which controls language.
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b)
One other finding from this study is that if two objects are placed simultaneously one in each
hand and then hidden in a pile of objects, each hand will select their own object but ignore
the other.
8a)
A ‘split-brain’ patient could not describe in speech material presented to their LVF because
this is dealt with by the right hemisphere which has virtually no language capacity.
b)
Patients did not suffer difficulties in their everyday life because they would have the time to
move their eyes and all information could therefore be received by both visual fields and
processed by both hemispheres.
9a)
The sample was a group of patients who suffered from severe epileptic seizures which could
not be controlled by medication, so they had had hemispheric deconnection to reduce the
severity of their seizures.
b)
One problem with generalizing from this sample is that it is unclear whether they had
suffered brain damage from the severe seizures they had experienced, which may make
their brain function different from that of others.
10a)
Patients seeing visual material presented to their LVF could not describe it because this is
processed by the right hemisphere which has limited or no language function.
b)
One conclusion from this finding is that the right hemisphere has virtually no language
capacity, and therefore if ‘normal’ people can describe material presented to their LVF, the
information must have passed across the corpus callosum.
11a)
One piece of evidence that supports this is that if two objects are placed simultaneously one
in each hand and then hidden in a pile of objects, each hand can only identify the item it
previously held and will ignore the other.
b)
One piece of evidence that challenges this is that objects named out loud can be identified
by both hands, showing that some functions are only partially bilateral and therefore the
opposite hemisphere may have a limited knowledge of the information the other one has.
12a)
One piece of evidence to support this is that participants could not name items flashed to
their left visual field, which is processed by the right hemisphere, indicating that it does not
have significant language capability.
b)
One function controlled by the right hemisphere is spatial construction.
13a)
One reason the data may not be reliable is that the sample has unique characteristics in
terms of the magnitude of the seizures they had experienced, so their brain function may
have been altered in such a way that another sample would produce differing results.
b)
One reason the data may not be valid is because the way the participants react in such an
unusual situation (one eye covered, in a lab setting, doing tasks not obviously reflective of
everyday life) is not a valid way of measuring their experiences every day.
14a)
Two behaviours controlled by the left hemisphere are speech and writing.
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b)
One piece of evidence that supports this is that participants could describe in speech and
writing items which were shown to their right visual field, which is processed by the left
hemisphere.
15a)
The IV in this study was whether the patient had hemispheric deconnection or not.
b)
This could not be manipulated because it would be unethical to perform this operation for
the purposes of research, so the researcher had to select patients who had already had it
carried out.
16a)
One way in which the sample may be representative is that lateralization and the functions
of the hemispheres are considered to be the same for all humans, so it is likely that the
effects of the hemispheric deconnection would be no different for other people than for
these few participants.
b)
One way in which the sample may be unrepresentative is that it is unclear whether they had
suffered brain damage from the severe seizures they had experienced, which may make
their brain function different from that of others.
17a)
One function exclusive to the right hemisphere is spatial awareness; one exclusive to the left
is speech.
b)
This lateralization may cause a problem for some people because if a brain injury or damage
resulting from disease is experienced in one hemisphere, the other may not have the
capacity to take over any loss of function.
18a)
He meant that people’s brains work, to an extent, in ways unique to them, and so does their
ability to make up for any loss of brain structure or function.
b)
One piece of evidence to support this is that some patients display ipsilateral control, i.e.
each hemisphere controls the same side of the body.
19a)
Two structures severed in the split-brain operation were the cerebral commissures which
connect the left and right hemispheres of the brain.
b)
Normal patients can say what they see in their left visual field because the information from
the eyes can pass across the corpus callosum to allow both hemispheres to be aware of it.
20a)
One way in which the study lacked ecological validity was that the method for collecting
data, where the data was flashed so briefly, would not happen in everyday life.
b)
It was appropriate because otherwise the participant could move their eyes so both
hemispheres would receive the information and the point of the study would be lost.
Section B
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1.
Previous research has indicated that the brain is divided into two halves called
hemispheres. The right and left hemispheres (RH and LH) of the brain communicate with
each other via a small group of connections. The main connection is the corpus callosum.
The importance of communication between the hemispheres is that otherwise you have, in
essence, two brains that can function independently. However, there are difficulties because
many functions are cross-wired, for example the right hand is controlled by the left
hemisphere. Other functions, such as language, are lateralised. Severing the links between
the two hemispheres has been found to limit epileptic seizures.
2.
The aim of the study was to look at the psychological effects of hemispheric deconnection in
split-brain patients, and to use the results to understand how the right and left hemispheres
work in ‘normal’ people.
3.
One hypothesis was that participants seeing information in their left visual field would not be
able to describe it because it is processed by the right hemisphere which does not have
language capabilities.
4.
This is a natural experiment (or quasi-experiment). It is an experiment because there is an IV
with different conditions (whether the patient has had the corpus callosum split) and a DV
(their abilities in the tasks). It is a natural experiment because these conditions were not
directly manipulated by the researcher, as Sperry did not carry out the operations for the
purposes of the research, but they had already been done for health reasons. This means
that Sperry could not allocate participants to the experimental condition.
5.
One strength of this is that it is the only realistic way of investigating split-brain patients, as
obviously the ethics involved would prevent this being done for research purposes. The fact
that it is an experiment with an IV means that cause and effect can be inferred, in this study
that impaired performance on the tasks is due to the severing of the corpus callosum.
6.
One weakness is that because this is a quasi-experiment, individual differences may have
affected the participants’ abilities in the tasks.
7.
The sample was a group of patients who had suffered from severe epileptic seizures which
could not be controlled by medication; they had had a commissurotomy to relieve this.
8.
The sample was an opportunity sample, meaning that they were available from the very
small relevant population for Sperry to use in research rather than being randomly selected
or volunteering.
9.
This is a reasonable number of participants given the small size of the target population and
the rarity of the procedure they had undergone.
10.
As they were all originally epilepsy sufferers, this may have caused differences in their brain
or performance which would not apply to others, so generalisation may be problematic.
11.
This is a snapshot study because it takes just one set of data for each experiment, and
captures the participants’ behaviour at one moment in time. It does not take account of
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development over time In this study, it shows people’s abilities in the tasks and does not
take account of how those abilities may change over time.
12.
One strength of snapshot studies is that they are quick to carry out, so Sperry could gain all
his data at once. This allowed him to draw rapid conclusions about the effect of the splitbrain state on the ability to perform various naming and touch tasks.
13.
Snapshot studies do not allow the researcher to discover whether results are due to the
development of the behaviour or to individual differences. In the Sperry study the
participants will have had different experiences during their epilepsy and operation, and the
brain does have some plasticity which may alter abilities in a way only revealed by studying
participants over time.
14.
One ethical issue is psychological harm: participants might have felt more abnormal after
the tests were done and this could lower their self-esteem, especially if they perceived
themselves as having done badly. The researchers might have counselled them afterwards
to help their self-esteem. Another ethical issue is privacy: it should not be possible to identify
who the individuals were so no names were mentioned, although one could question
whether the initials gave too much of a clue considering the tiny target population.
15.
The participants had one eye covered and were asked to gaze at a fixed point in the centre
of a projection screen. Visual stimuli were projected onto the screen, either to the right or
left of the screen at a very high speed – one picture every 0.1 second or less. This meant
that the information was only received by one visual field. Various tasks were carried out
including flashing words partly to the LVF and partly to the RVF, and then noting whether the
participants could say the word or select the object with the same hand.
16.
One change to this study could be to observe split-brain patients in their everyday lives to
see how their condition might affect them. They could be watched doing ordinary tasks in
ordinary conditions, e.g. preparing and eating food, cleaning, interacting with family
members, etc.
Another change to this study would be to use many more patients, for example 30, which
would be a more representative number but still realistic given the nature of the target
population.
17.
The first change would make the study more ecologically valid. Also, it might reveal some
everyday behaviours which were affected by having a split brain, which on a superficial
inspection seemed quite normal.
This would probably show overall similar findings and would also help explore the individual
differences between the participants and discover whether there was any pattern or reasons
for why some participants could show ipsilateral control (right hemisphere communicating
with right hand).
18.
Qualitative data included comments made by the participants such as ‘This hand is numb’,
and descriptions of how the participants behaved in response to the tasks such as that both
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hands could select their own object but ignored each other’s if two objects were placed
simultaneously in them.
19.
The qualitative data provided detail which was useful to Sperry as it described the
participants reactions in ways which numerical data could not, including insight into what
the patients ‘knew’ with each hemisphere.
20.
One weakness is that it makes this data difficult to analyse and to represent in a concise
clear fashion; it is not easy to categorise or draw themes from diverse comments made by
the patients.
21.
The results of this study were that if a projected picture is shown and responded to in one
visual field, it is only recognised again if it appears in that visual field (VF). If visual material
appears in the right visual field (RVF, processed by left hemisphere), the participant could
describe it in speech and writing as normal. If the same visual material is projected to the
left visual field (LVF, processed by the right hemisphere) then the participant says he did not
see anything or says there was just a flash of light on his left side. (Language centres are in
the left hemisphere.) If you then ask the same participant to use his left hand (right
hemisphere control) to point to a matching picture or object in a collection of
pictures/objects, he points to the item he just insisted he couldn’t see. These results
confirm that the right hemisphere cannot speak or write (called aphasia and agraphia
respectively).
22.
Laboratory experiments are easy to replicate using the standardised procedures and
equipment of the initial study. All of the procedures of the mini-experiments were clear and
specific. In this way, Sperry’s study would be replicable and in fact has been repeated and
shown consistent results. However, it would obviously be hard to find an equivalent sample
and the small size of that sample may mean that the same results from another group may
not be obtained due to individual differences.
23.
The innovative equipment and task paradigm creates high validity for this study as it
provides a way in which only one hemisphere becomes aware of the information; therefore
the performance of the participants is a genuine reflection of the capabilities of that
hemisphere. However, the fact that the patients had had their operation a variety of
different lengths of times previously means that some of them may have developed
compensatory strategies that others did not, which may have affected the results.
24.
The tasks used in Sperry’s study are not ecologically valid as the patients in their real life
would always be able to access information with both hemispheres by using both visual
fields following relevant eye movements. In everyday life they show little impairment due to
this, so the study could be said to tell us little about their ‘normal’ lives and abilities.
However, in this case it could be said to be still appropriate because Sperry was aiming to
contribute to the theoretical knowledge about the brain’s structures and functioning, which
he has achieved.
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Section C
1.
One assumption of the biological approach in psychology is that much of human behaviour
is governed and can be explained by biology, e.g. hormones, genes, neurotransmitters, brain
structure and so on. This means we probably have less control and free will than we would
like to think.
2.
The physiological approach could explain the difficulties experienced by split-brain patients
because it indicates how the brain controls various behaviours from one hemisphere or the
other, so the lack of a pathway for this information to travel between the two affects
capability in various tasks. This is shown by Sperry’s study where a physical alteration in the
brain causes impairment in language and touch-based tasks.
3.
One similarity with Maguire is that both studies are quasi-experiments, meaning that the IVs
are naturally occurring rather than being deliberately manipulated by the researcher. In
Maguire, the two groups are taxi drivers and non-taxi drivers, which is a pre-existing state.
Similarly, in Sperry, the participants have already had the split-brain operation to control
epilepsy so they were not allocated to the condition by the researcher.
One difference between Dement and Kleitman’s study and Sperry’s is that the former is
monitoring ongoing, ‘live’ changes in brain activity. The EEG shows differing levels of activity
in the brain as it is really happening, second by second, (akin to ‘live TV’). In contrast,
Sperry’s study looks at a static state, namely the abilities of the two hemispheres once they
have been separated.
4.
One strength of the biological approach is that it is scientific. It probably represents the most
scientific end of psychology. This means that it is objective, usually empirically based and
widely respected. For example, in Sperry, the tightly controlled procedure and environment
as well as the specially designed equipment creates a very scientific procedure. Because all
these aspects of the procedure increase the validity and objectivity of the research, it is
widely accepted and respected.
Another strength of the biological approach is that it generally produces useful contributions
to psychology – both in terms of applications and in terms of usefulness for helping further
research in the area. For example, Sperry’s work generating knowledge about different parts
of the brain could be used to better understand people who have suffered brain damage in,
for example, a car accident. Also, sometimes people need to have brain tumours removed
and surgeons need to know the effects of removing parts of the brain.
One weakness of the biological approach is that it can be reductionist – only looking at
simple explanations. For example, in Sperry, the participants’ success in the tasks is taken
purely as evidence for the effects of the commisurotomy. It could be said that this is
reductionist as it only looks at the simple explanations and ignores more complex
psychological explanations or considerations of how the participants feel or the wider effects
on their lives.
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Another weakness of the physiological approach is that it overlooks nurture and overemphasises nature. For example, in Sperry’s study the focus is on the physical structure of
the brain and does not take into account compensatory strategies used by the patient or
possible neuroplasticity which may develop over time (‘nurture’).
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