AQA Psychology for A Level Year 2 - Student Bk

Concepts: Jet lag On page 47, we noted the unpleasant and potentially dangerous effects of shift work on the body’s biological clock. Jet lag is another important form of desynchronisation that can disrupt the sleep/wake cycle, causing sleeplessness, irritability and nausea, as the body struggles to adapt to changing time zones. Question Using research into endogenous pacemakers, what advice would you give would-be travellers on how best to minimise the negative effects of jet lag? @ookx hs @ookx hs Methodological issues in studies The findings from the Campbell and Murphy study have yet to be replicated . Other psychologists have been critical of the manner in which the study was conducted and have suggested that there may have been some limited light exposure to the participants’ eyes – a major confounding variable . Also, isolating one exogenous zeitgeber (light) in this way does not give us insight into the many other zeitgebers that influence the sleep/wake cycle, and the extent to which these may interact. Consider: As well as light and social cues, what other exogenous zeitgebers may affect the sleep/ wake cycle? Interactionist system Only in exceptional circumstances are endogenous pacemakers free-running and unaffected by the influence of exogenous zeitgebers. Total isolation studies, such as Siffre’s cave study, are extremely rare and could be judged as lacking validity for this reason. In real-life, pacemakers and zeitgebers interact, and it may make little sense to separate the two for the purpose of research. Consider: Explain how endogenous pacemakers and exogenous zeitgebers interact in the context of the sleep/wake cycle. Evaluation e X tra 1. With reference to an example, define what is meant by an endogenous pacemaker . [3 marks] 2. Describe one study that investigated the effect of an exogenous zeitgeber on the sleep/wake cycle. [4 marks] 3. Discuss the effect of endogenous pacemakers and exogenous zeitgebers on the sleep/wake cycle. [16 marks] Check It Methods: Delayed sleep-phase disorder Delayed sleep-phase disorder (DSPD) is a circadian rhythm sleep disorder affecting the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms. People with DSPD generally fall asleep some hours after midnight and have difficulty waking up in the morning. Patients can sleep well and have a normal need for sleep. However, they find it very difficult to wake up in time for a typical school or work day. Twenty patients who suffered from DPSD were involved in an investigation. Researchers randomly allocated the 20 patients into two groups: Group A (the treatment group) and Group B (the control group). Group A were given a course of drugs that increased melatonin production for six weeks at bed-time (around 11pm). Group B were given a placebo for the same period of time. At the end of the six-week period, all the participants were assessed on a number of self-report measures. These examined their performance at work, their attention levels during the day and their relationship with their families. Questions 1. Suggest an appropriate hypothesis for the investigation above. ( 2 marks ) 2. Identify the experimental design in the investigation above. ( 1 mark ) 3. Explain one strength and one limitation of the experimental design you have identified in question 2. ( 4 marks ) 4. Explain one way in which participants may have been randomly allocated to one of the two groups. ( 2 marks ) 5. Explain one limitation with the use of self-report measures described above. ( 3 marks ) @ookx hs @ookx hs Evaluation Beyond the master clock Research has revealed there are numerous circadian rhythms in many organs and cells of the body. These are called peripheral oscillators , and are found in the adrenal gland, oesophagus, lungs, liver, pancreas, spleen, thymus and skin. Although these peripheral clocks are highly influenced by the actions of the SCN, they can act independently. Francesca Damiola et al . (2000) demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the liver by up to 12 hours, whilst leaving the rhythm of the SCN unaffected. This suggests that there may be many other complex influences on the sleep/ wake cycle, aside from the master clock (the SCN). Ethics in animal studies On previous spreads we have made reference to the problems involved in generalising findings of the sleep/wake cycle from animal studies to humans. A more disturbing issue, however, particularly in relation to the DeCoursey et al . study, is the ethics involved in such research. The animals were exposed to considerable harm, and subsequent risk, when they were returned to their natural habitat. Whether what we learn from investigations such as these justifies the aversive procedures involved is a matter of debate. Influence of exogenous zeitgebers may be overstated Laughton Miles et al . (1977) recount the story of a young man, blind from birth, with a circadian rhythm of 24.9 hours. Despite exposure to social cues, his sleep/wake cycle could not be adjusted, and consequently, he had to take sedatives at night and stimulants in the morning to keep pace with the 24-hour world. Similarly, studies of individuals who live in Arctic regions (where the sun does not set during the summer months) show normal sleep patterns despite the prolonged exposure to light. Both these examples suggest that there are occasions when exogenous zeitgebers may have little bearing on our internal rhythm. It’s probably reasonable to assume that this man has some difficulty adjusting to his sleep/wake cycle. endogenous pacemakers and exogenous zeitgebers 51 •