AQA Psychology for A Level Year 2 - Student Bk

Remember, when asked about ‘research’, within this or any other section, you can refer to both theories/explanations and/or research studies as part of your answer. So writing about ‘research into circadian rhythms’ you could include details of specific studies (such as Siffre’s case study) as well as broader explanations of the effects of such rhythms. Study tip The specification says… Biological rhythms: Circadian rhythms Biological rhythms: circadian rhythms. A biological rhythm is a change in body processes or behaviour in response to cyclical changes within the environment. For instance, most of us show a distinct pattern of going to sleep when it’s dark and waking up when it’s light. This is an example of a circadian rhythm – a specific type of bodily rhythm that occurs across a 24-hour period. Key terms Biological rhythms – Distinct patterns of changes in body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers). Circadian rhythm – A type of biological rhythm, subject to a 24-hour cycle, which regulates a number of body processes such as the sleep/wake cycle and changes in core body temperature. Circadian rhythms Biological rhythms All living organisms – plants, animals and people – are subject to biological rhythms and these exert an important influence on the way in which body systems behave. All biological rhythms are governed by two things: the body’s internal biological ‘clocks’, which are called endogenous pacemakers and external changes in the environment known as exogenous zeitgebers (see page 50). Some of these rhythms occur many times during the day ( ultradian rhythms ). Others take longer than a day to complete ( infradian rhythms ) and in some cases much longer (circannual rhythms). Our focus on this spread is on circadian rhythms – those rhythms that last for around 24 hours (circa meaning ‘about’ and diem meaning ‘day’). Two examples of circadian rhythms are the sleep/wake cycle and core body temperature (see Apply it, below). The sleep/wake cycle The fact that we feel drowsy when it’s night-time and alert during the day demonstrates the effect of daylight – an important exogenous zeitgeber – on our sleep/wake cycle. However, what if the biological clock was ‘left to its own devices’ without the influence of external stimuli such as light (what researchers refer to as ‘free-running’)? If we had no idea whether it was night or day would we still fall asleep and wake up at regular times? Several studies have tried to answer this question. Siffre’s cave study Michael Siffre (pronounce ‘ Seef ’) is a self-styled caveman who has spent several extended periods underground to study the effects on his own biological rhythms. Deprived of exposure to natural light and sound, but with access to adequate food and drink, Siffre re-surfaced in mid- September 1962 after two months in the caves of the Southern Alps believing it to be mid-August! A decade later he performed a similar feat but this time for six months in a Texan cave. In each case, his ‘free-running’ biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours) though he did continue to fall asleep and wake up on a regular schedule. Other research Similar results were recorded by Jürgen Aschoff and Rütger Wever (1976) who convinced a group of participants to spend four weeks in a WWII bunker deprived of natural light. All but one of the participants (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24 and 25 hours. Both Siffre’s experience and the bunker study suggest that the ‘natural’ sleep /wake cycle may be slightly longer than 24 hours but that it is entrained by exogenous zeitgebers associated with our 24-hour day (such as the number of daylight hours, typical meal-times, etc.). Despite this, we should not overestimate the influence of environmental cues on our internal biological clock. Simon Folkard et al . (1985) studied a group of 12 people who agreed to live in a dark cave for 3 weeks, retiring to bed when the clock said 11.45pm and rising when it said 7.45am. Over the course of the study, the researchers gradually speeded up the clock (unbeknown to the participants) so an apparent 24-hour day eventually lasted only 22 hours! It was revealed that not one of the participants was able to comfortably adjust to the new regime. This would suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by changes in the external environment. Concepts: Core body temperature Core body temperature varies by around two degrees centigrade during the course of a day. It is at its lowest around 4 in the morning (36 o C) and peaks around 6 in the evening at 38 o C. Evidence suggests that body temperature may have an effect on our mental abilities: the warmer we are (internally), the better our cognitive performance. Folkard et al . (1977) demonstrated how children who had stories read to them at 3pm showed superior recall and comprehension after a week compared to children who heard the same stories at 9am. Similarly, Gupta (1991) found improved performance on IQ tests when participants were assessed at 7pm as opposed to 2pm and 9am. Question Given the results of these studies, when would be a good time of day to take your psychology exam? @ookx hs @ookx hs Michael Siffre – the man, the cave, the beard. Chapter 2 Biopsychology 46 •