Flashcards in A2 Biopsychology - Biological Rhythms Deck (6)
Describe circadian rhythms and their supporting studies.
Circadian rhythms occur once every 24 hrs, e.g. the sleep-wake cycle. Melatonin is a neurotransmitter that makes us sleepy, and the production of which is inhibited in daylight i.e. less inhibition in darkness. S/w cycle is controlled by SCN (endogenous pacemaker); a bundle of nerve cells in the hypothalamus which communicates w/ the pineal gland which produces melatonin
Siffre (1962) spent 2 months in a cave and found that without light his s/w cycle settled at around 25 hours.
Aschoff and Wever (1976) had ppts spend 4 weeks in a WW2 bunker and found that without natural daylight, one ppt's s/w cycle settled at 29 hrs whilst everyone else's settled between 24 and 25 hrs.
=> both of these studies show that the s/w cycle is around 25 hrs
Folkard (1985) had 12 ppts live in a cave for 3 months and had them go to sleep at 11:45 each night and wake up at 7:45 each morning. Folkard would slowly adjust the alarm clocks of the ppts over the 3 months and by the end the "day" was only 22 hrs long. None of the ppts could adjust which shows that the s/w cycle is a strong, powerful circadian rhythm.
Evaluate circadian rhythms
(+) Real life application; shiftworkers now get a set amount of days to "reset" to normal times.
(-) Poor sample sizes in studies so poor generalisability.
(-) Ppts still had access to varying degrees of artificial light which we now know can disrupt the s/w cycle so extraneous variable so decreased validity.
(+) Can be applied to chronotherapeutics; if drugs are taken at the right time in accordance with the circadian rhythms then they can be more effective. E.g. heart attacks are most common in early morning hours after awakening, so drugs can be taken at 10pm the night before but not released until about 6am
(-) Individual differences; Duffy et al found some people are genuinely “morning people” and will naturally get up earlier and vice versa
Describe infradian rhythms and its supporting study
Infradian rhythms occur less than once per 24 hrs, e.g. the menstrual cycle. On day 1, the womb lining sheds. An increase in oestrogen encourages the ovaries to produce an egg and also causes an increase in progesterone which makes the womb lining thick and sticky in preparation for pregnancy. If no pregnancy occurs then womb lining sheds (back to day 1). Cycles can vary from 23-36 days among women
Stern and McClintock (1998) had C(regular period) wear cotton wool under their arms all day, repeating for 30 days. At the end of each day the sweat-soaked cotton wool would be wiped under the noses of C(irregular period). Due to pheromones present in the sweat, 60% of C(irregular) synced up with their designated C(regular) partner, despite not spending any time together.
Evaluate infradian rhythms
(+) There is thought to be an evolutionary benefit to syncing up cycles; if all females have children at the same time and some of the mothers then die, the others could raise the children together (collaborative parenting)
(-) However, if all females are fertile at the same time then they would all be going for the same male (the one with the best genes/characteristics) at the same time, so evolutionary benefit is questioned.
(+) Penton-Voak et al found that mate preferences in women can be influenced by what stage of the menstrual cycle they’re in; women generally preferred a “slightly femininised” face when looking for a long term partner but often chose more masculine ones when in the ovulatory stage
(-) PMS (part of the menstrual cycle) can influence accidents, crime and even suicide rates
=> Rodin has also criticised the idea of PMS in general, arguing it’s a patriarchal social construction designed to favour men and make women seem weak
(+) Stern and McClintock’s research was ground-breaking and sparked a new debate in psychology around synchronisation; gave good empirical evidence for the idea of synchronised cycles and changed the way researchers viewed the cycle
Describe ultradian rhythms
Ultradian rhythms occur more than once every 24 hrs e.g. the stages of sleep. In each 90 min cycle there are 5 stages, which can be measured using EEGs
1) Drowsy sleep - alpha waves and later on theta waves about 4-5% of the cycle; resembles relaxed wakefulness and is often accompanied by myoclonic jerks (sudden body jerks), sensations of falling and opening/rolling their eyes
2) First "real" stage of sleep; conscious awareness of the outside world fades. Mainly theta waves. About 45-55% of the cycle. Sporadic bursts of brain activity (sleep spindles) appear, muscles are relaxed and breathing is steady. Will typically deny having been asleep if awoken in this stage
3) Delta waves (which are slower than theta waves). Even less responsive to the outside world. About 4-6% of the cycle.
4) Even deeper, slow-wave sleep. Delta waves. Even more difficult to awaken. About 12-15% of the cycle. Stage 3 and 4 are called “slow wave sleep” and other than occasional hand or foot twitches, the person is very still and in deep sleep.
5) Brain activity speeds up (REM sleep). Brain waves more similar to those during the waking state. About 20-25% of the cycle. Body has “flaccid paralysis”; it doesn’t respond much to being touched, and eyeballs move quickly under the eyelids. Muscles twitch and breathing becomes more rapid. REM sleep is often thought to be “dream sleep” and people woken up during REM will often report dreaming