Case studies Flashcards
Stephan and Zucker (1972)
Circadian Rhythms
Stephan and Zucker investigated the effects that damage to the SCN has on circadian rhythms.
They contained rats in a laboratory with 12 hours of light (fluorescent lights) and 12 hours of dark, and free access to food and water. They showed a circadian rhythms of drinking and locomotor activity (movement from one place to another).
Some rats received bilateral leisons directed the SCN (to damage the SCN). In all experiments water intake was measured to the nearest ml daily. The number of revolutions traversed by the rats in the running wheels was recorded on counters that were read daily.
When the group of rats with damage to the SCN were compared to the normal controls, they found that damage to the SCN eliminated the typical circadian patterns of drinking, eating and activity of the rat.
Weakness: Ethical issues- the study was extreme considering the number of rats that died.
Weakness 2: Methodological issues- other parts of the hypothalamus was also damaged to prove that this did not affect circadian rhythms and did not influence the results of the study.
The surgical procedure was difficult and only 11 out of 25 rats survived.
Possible that the harshness of the surgical operation might have influenced the rat’s behavior.
Results to this research may not be applicable to humans.
Strength: Shows the significance of the SCN in circadian rhythms, and the potential impact on physiological and behavioral activities that damage to the SCN has. This information helps other psychologists and researchers in their own investigations.
Siffre (1975)
Circadian Rhythms
Michel Siffre conducted a study to see the effects of the absence of exogenous zeitgebers, on biological rhythms. He spent 179 days/6 months in an underground cave in texas.
There was no light so the absence of this zeitgeber meant that the biological rhythms were free running.
A variety of physiological functions were recorded: body temperature, heart rate, blood pressure and sleep-wake pattern.
Two key findings:
His standard 24 hours sleep-wake cycle expanded to 25-32 hours. His days became longer and on the 179th day he thought it was only the 151st day.
His body temperature circadian rhythm was more stable, it extended slightly to about 25 hours but stayed consistent.
We usually go to sleep when body temperature is falling and wake up when it’s rising but Siffre’s sleep-wake cycle became desynchronized from his body temperature rhythms.
He concluded, that in the absence of exogenous zeitgebers, endogenous pacemakers can still regulate biological rhythms but it is not perfect.
Weakness: Ethical issues- Siffre reported feelings of depression, suicidal thoughts and memory problems as little as 80 days into the study.
Weakness 2: Methodological issues- this case study is only on one man, so the results cannot be fully generalized.
Strength: Other studies support these findings. Aschoff (1965) found that students in an underground bunker under similar conditions as Siffre also extended (their day) to between 25 and 27 hours.
McClintock et al. (1971)
Infradian rhythms
The aim of the study is to show that the menstrual cycle is influenced by the pheromonal secretions from other women.
The study was conducted on female university students not taking birth control pills, using a quasi-experimental design (participants are not randomly assigned) with independent measures.
The control group of women wore an
alcohol soaked pad in their armpits. The fumes
from these were inhaled by women in the experimental group and their menstrual cycles were monitored.
The menstrual cycle of the experimental group who inhaled secretions of women who were about to ovulate, became shorter, where as when they inhaled secretions from women who had just ovulated, their menstrual cycle became longer.
In conclusion, the experimental groups’ menstrual
cycles were affected by the secretions from the
control group. This explains why when a group
of women live in close proximity their menstrual
cycles tend to synchronise.
Weakness: Although their finding prove that menstrual cycles are influenced by exogenous zeitgebers, it is not clear why this happens and how it happens (human response to pheromones is not yet well understood).
Weakness 2: No physiological data collected.
Weakness 3: Trevathan et al (1993) carried out a similar study on whether homosexual partners had
their cycles synced and found that they didn’t
Weakness 4: Yang and Shank (2006) for almost a year, researchers collected data on menstrual cycles from 186 Chinese women living in dorms. They discovered that women who lived in groups did not have their cycles synchronized. Second, they looked at the first research on menstrual synchrony. In that study, they discovered that group synchronization was purely random. They then show that cycle variability causes cycle beginningsto converge and subsequently diverge, which could explain impressions of synchrony.
Strength: There is a large sample size which means the accuracy of the study is increased and there is a small margin of error.
Dement and Kleitman (1957)
Ultradian rhythms
Dement and Kleitman (1957) discovered that REM sleep was associated with dreaming. They conducted an experiment on 9 adult participants (7 male and 2 female). The aim of this study was to see if the physiological aspects of REM sleep related to the participant’s psychological experience of dreaming.
They woke up participants at various times, and found that those that were woken during REM sleep reported dreaming around 80 per cent of the time. Where as, those woken during NREM sleep reported dreaming only 20 per cent of the time.
Additionally, the dreams during REM sleep were found to be far more vivid than the ones during NREM.
Weakness: Since this study, REM has been perceived as ‘dreaming sleep’, which is inaccurate as they are very different. REM is a physiological state identified by scientific measures of brain and body activity, whereas dreams are ‘subjective’, and there is no actual method of recording.them and this means scientific psychology has difficulties studying dreams and their functions.
Strength: ethics- Right to withdraw, after two days 4 left.
Strength 2: High level of control - the researchers controlled many extraneous variables such as not drinking alcohol or caffeine before the experiment, waking up participants with the same doorbell sound and having participants in the same environment. This makes the results valid and reliable.
Strength 3: Replicable - it was a laboratory experiment conducted with the use of scientific equipment so this makes it easier to replicate the study and check for reliability.
Weakness: low ecological validity - the environment where participants were studied was artificial. They slept in a laboratory with electrodes on their head and face and were woken up by a doorbell. This may have affected the results as it could have caused demand characteristics and the realism of the study was lowered.
Weakness 2: Low generalizability - the results cannot be generalised to the wider population because only 9 people were studied, therefore the sample was too small and the result may have been individual. Also, there was no diversity in age, ethnicity and sex.
Schwartz et al. (1995)
Jet lag
Schwartz (1995) studied the possible negative effects of jet lag on athletic performance by focusing on US baseball teams.
They studies results over a three-year period and showed that teams travelling east to west before a game won 44 per cent of their games, where as those travelling west to east only won 37 per cent.
The reason for this is because when travelling east to west the body clock is ahead of local time and simply has to wait, whereas when travelling west to east the body clock ends up behind local time and has to catch up. The body clock finds it easier to wait than it does catching up.
Weakness: An extraneous variable in this study would be the skills of the players, however the length of the study (3 years) means that this variable should have evened itself out. However there is still a possibility that this variable influenced the results of this study.
Weakness: the results from this study cannot be generalized to the wider population as this is a study only conducted on men only and even more specifically on athletic performance.
Strength:
Czeisler et al. (1982)
Shift work
Czeisler et al. (1982) introduced a forwards shift rotation which is similar to phase delay in jet lag, in which flying east to west requires us to delay our sleep in order for our biological rhythm (body clock) to resynchronize our body clock with the external zeitgebers.
Similarly to how phase advance is considered more difficult to adjust to than phase delay, Czeisler came up with this forward shift rotation in hopes that it would have a similar effect and be easier than the traditional backwards shift rotation.
The backward shift rotation had 7 days in each rotation and workers reported high levels of stress, sleep difficulties and health problems which all negatively impacted their productivity. To help them overcome this, Czeisler increased the time between changes in shift time to 21 days so that the workers would have more time to adjust properly to the new times.
After 9 months, the same workers at Utal chemical plant who originally claimed to suffer health problems now reported feeling less stress, with less sleep difficulties and health problems, and increased productivity.
Weakness: Cannot be generalized because it is only on Utal chemical plant workers who all work the same job therefore require similar abilities.
Weakness 2: May not be valid or reliable today, sinc eth study was conducted in 1982 and since then there have been a lot of changes including technology innovations which plays a major role in the lifestyle of people nowadays.
Strength: This study is supported by Gordon et al. (1986), who found similar results in a study on Philadelphia police officers. In which he moved them from a backward shift rotation to 18 days on a forward shift rotation and found that there was a 30 per cent reduction in sleeping on the job and a 40 per cent reduction on accidents on the job. The officers reported better sleep and less stress.
Lesku et al. (2006)
Evolutionary explanations
Leksu et al. analyzed data on sleep patterns from 54 species and looked at a range of variables, including: body mass
brain mass
basal metabolic rate (BMR)- the rate of energy expenditure that is carried out when the person is at a state of rest
sleep exposure index- assessment of animal’s sleep site and its level of safety
trophic position- herbivore or carnivore
This study consists of measurements and observations os sleep patterns in many species, in which the measurements cover ecological niche, physiological characteristics (body size, brain mass, BMR), and EEG recordings of REM and NREM sleep.
Key findings:
Brain mass is positively correlated with the amount of REM sleep, but it has no association with NREM. Animals with larger brains have more REM sleep.
The sleep exposure index is negatively correlated with the amount of REM sleep. The more dangerous the sleep site is the less REM sleep.
Trophic position was correlated with the amount of REM and with the total sleep time. Herbivores overall has less REM and total sleep time than carnivores.
BMR is negatively correlated with NREM and total sleep time.
Body mass is negatively correlated with sleep time. Large animals sleep less than small animals.
Weakness: methodological issues- the results in this research are based on correlations between variables. Although strong correlations can establish a powerful relationship between variables, a correlational design cannot say whether the relationship is ‘cause and effect’. To establish this, the use of controlled experiments would be required.
Strength: high ecological validity - the research is based on observations of animals in their natural habitat.
Advantage of evolutionary explanations: an advantage of the evolutionary approach with its focus on ecological factors is that it takes the whole animal and its lifestyle into account. Therefore, it is not a reductionist approach.
