PAPER TWO: BIOPSYCHOLOGY
TOPIC: Circadian rhythms
A01:
Circadian rhythms = biological rhythms that are subject to a 24-hour cycle (like the
sleep/wake cycle) and regulate a number of body processes
RESEARCH: SIFFRE:
- 6 months in a cave with no natural light/cues (had artificial light)
- Settled into a sleep/wake cycle of between 25 to 30 hours
- Absence of external cues altered his circadian rhythm
- When he returned, believed the date to be a month earlier than it was
- Suggests that his 24 hour sleep/wake cycle was increased by a lack of external cues,
so ez’s needed to keep the 24 hour cycle
- Supports the idea we have a free running circadian rhythm regulated by internal
factors
RESEARCH: ASCHOFF & WEVER:
- Studies p’s living in a bunker, only artificial light
- Settled into a longer sleep/wake cycle of between 25 to 27 hours
- Suggests humans use natural light (ez) to regulate a 24 hour circadian sleep/wake
cycle
- All but 1 of the p’s displayed a circadian rhythm of 25-27 hours, suggesting there may
be innate individual differences in circadian rhythms
RESEARCH: FOLKARD ET AL:
- Studied 12 people living in a dark cave for 3 weeks
- Retired to bed at 11:45 and rose at 7:45
- Researchers gradually speeded up the clock so a day eventually lasted 22 hours
- Only 1 of the p’s was able to adjust to the new regime
- Suggests an existence of a strong free running circadian rhythm that cannot be
overridden by changes in the environment
A03:
X - Biologically reductionist
Behaviourist approach would suggest that bodily rhythms are influenced by other people and
social norms
Therefore, the research evidence could be criticised for being reductionist as it only
considers a singular biological mechanism and fails to consider the other widely divergent
viewpoints
✓ - Real life application
Research into circadian rhythms means researchers have a better understanding of the
consequences that can occur as a result of their disruption (desynchronisation)
Night workers in shift work experience a reduced concentration around 6 in the morning,
meaning accidents are more likely
Research into the sleep/wake cycle may have economic implications in terms of how best to
manage worker productivity
✓ - Research support
,Morgan, bred hamsters so they had a circadian rhythm of 20 hours, SCN neurons
transplanted into normal hamsters who displayed the same 20 hour cycle
However, difficult to generalise (animal study), humans would respond differently as we are
different biologically
Demonstrates significance of SCN but unable to explain the importance of ep’s on the
sleep/wake cycle in humans
✓ - Evidence suggests that circadian rhythms also co-ordinate a number of the body’s basic
processes
Has an effect on pharmacokinetics (action of drugs on the body and how well they are
absorbed/distributed), research into circadian rhythms revealed there are peak times when
drugs are likely to be most effective
Led to the development of guidelines to do with timing of drug dosing for a whole range of
medications
, PAPER TWO: BIOPSYCHOLOGY
TOPIC: Infradian and ultradian rhythms
A01:
Infradian rhythms = type of biological rhythm with a frequency of less than one cycle in 24
hours
Ultradian rhythms = type of biological rhythm with a frequency of more than one cycle in 24
hours
Pheromones = substances which are secreted to the outside by an individual and received
by a second individual
Menstrual cycle (Infradian):
- Has a frequency of less than one cycle completed in a 24 hour period, typical cycle =
28 days
- Governed by monthly changes to hormone levels which regulate ovulation
- Endogenous system but evidence suggests it may be influenced by exogenous
factors such as the cycles of other women
STUDY: STERN & MCCLINTOCK:
- Menstrual cycles may synchronise as a result of the influence of female pheromones
- 29 women with a history of irregular periods
- Samples of pheromones gathered from 9 of the women via a cotton pad placed in
their armpit for 8 hours
- Pads were rubbed on the upper lip of 20 women
- 68% of the women experienced changes to their cycle which brought them closer to
the cycle of their odour donor
STUDY: REINBERG:
- Woman spent 3 months in a cave with a small lamp for light
- Her menstrual cycle shortened from 28 days to 25.7 days
- Suggests a lack of light affected her cycle, demonstrating the effect of external
factors on Infradian rhythms
Evolutionary advantages:
- Synchronised menstrual cycle = synchronisation of pregnancies = childcare can be
shared
- Penton-Volk et al = women expressed a preference for feminised faces in least fertile
stage, more masculine at most fertile
- Indicate women’s sexual behaviour is motivated by their Infradian rhythms,
highlighting importance in relation to human behaviour
Seasonal affective disorder (SAD, Infradian):
- Particular type of Infradian rhythm known as circannual rhythm
- Experience of SAD may be due to the disruption of the sleep/wake cycle due to the
prolonged periods of darkness in the winter
- Hypothesised that melatonin is implicated, pineal gland secretes melatonin until
dawn when there is an increase in light
- Winter = lack of light in morning = secretion process continues for longer which
affects production of serotonin (associated with depressive symptoms)
STUDY: TERMAN:
- Rate of SAD more common in Northern countries where the winter nights are longer
- Affects 10% of people in New Hampshire (North) but only 2% in Southern Florida
TOPIC: Circadian rhythms
A01:
Circadian rhythms = biological rhythms that are subject to a 24-hour cycle (like the
sleep/wake cycle) and regulate a number of body processes
RESEARCH: SIFFRE:
- 6 months in a cave with no natural light/cues (had artificial light)
- Settled into a sleep/wake cycle of between 25 to 30 hours
- Absence of external cues altered his circadian rhythm
- When he returned, believed the date to be a month earlier than it was
- Suggests that his 24 hour sleep/wake cycle was increased by a lack of external cues,
so ez’s needed to keep the 24 hour cycle
- Supports the idea we have a free running circadian rhythm regulated by internal
factors
RESEARCH: ASCHOFF & WEVER:
- Studies p’s living in a bunker, only artificial light
- Settled into a longer sleep/wake cycle of between 25 to 27 hours
- Suggests humans use natural light (ez) to regulate a 24 hour circadian sleep/wake
cycle
- All but 1 of the p’s displayed a circadian rhythm of 25-27 hours, suggesting there may
be innate individual differences in circadian rhythms
RESEARCH: FOLKARD ET AL:
- Studied 12 people living in a dark cave for 3 weeks
- Retired to bed at 11:45 and rose at 7:45
- Researchers gradually speeded up the clock so a day eventually lasted 22 hours
- Only 1 of the p’s was able to adjust to the new regime
- Suggests an existence of a strong free running circadian rhythm that cannot be
overridden by changes in the environment
A03:
X - Biologically reductionist
Behaviourist approach would suggest that bodily rhythms are influenced by other people and
social norms
Therefore, the research evidence could be criticised for being reductionist as it only
considers a singular biological mechanism and fails to consider the other widely divergent
viewpoints
✓ - Real life application
Research into circadian rhythms means researchers have a better understanding of the
consequences that can occur as a result of their disruption (desynchronisation)
Night workers in shift work experience a reduced concentration around 6 in the morning,
meaning accidents are more likely
Research into the sleep/wake cycle may have economic implications in terms of how best to
manage worker productivity
✓ - Research support
,Morgan, bred hamsters so they had a circadian rhythm of 20 hours, SCN neurons
transplanted into normal hamsters who displayed the same 20 hour cycle
However, difficult to generalise (animal study), humans would respond differently as we are
different biologically
Demonstrates significance of SCN but unable to explain the importance of ep’s on the
sleep/wake cycle in humans
✓ - Evidence suggests that circadian rhythms also co-ordinate a number of the body’s basic
processes
Has an effect on pharmacokinetics (action of drugs on the body and how well they are
absorbed/distributed), research into circadian rhythms revealed there are peak times when
drugs are likely to be most effective
Led to the development of guidelines to do with timing of drug dosing for a whole range of
medications
, PAPER TWO: BIOPSYCHOLOGY
TOPIC: Infradian and ultradian rhythms
A01:
Infradian rhythms = type of biological rhythm with a frequency of less than one cycle in 24
hours
Ultradian rhythms = type of biological rhythm with a frequency of more than one cycle in 24
hours
Pheromones = substances which are secreted to the outside by an individual and received
by a second individual
Menstrual cycle (Infradian):
- Has a frequency of less than one cycle completed in a 24 hour period, typical cycle =
28 days
- Governed by monthly changes to hormone levels which regulate ovulation
- Endogenous system but evidence suggests it may be influenced by exogenous
factors such as the cycles of other women
STUDY: STERN & MCCLINTOCK:
- Menstrual cycles may synchronise as a result of the influence of female pheromones
- 29 women with a history of irregular periods
- Samples of pheromones gathered from 9 of the women via a cotton pad placed in
their armpit for 8 hours
- Pads were rubbed on the upper lip of 20 women
- 68% of the women experienced changes to their cycle which brought them closer to
the cycle of their odour donor
STUDY: REINBERG:
- Woman spent 3 months in a cave with a small lamp for light
- Her menstrual cycle shortened from 28 days to 25.7 days
- Suggests a lack of light affected her cycle, demonstrating the effect of external
factors on Infradian rhythms
Evolutionary advantages:
- Synchronised menstrual cycle = synchronisation of pregnancies = childcare can be
shared
- Penton-Volk et al = women expressed a preference for feminised faces in least fertile
stage, more masculine at most fertile
- Indicate women’s sexual behaviour is motivated by their Infradian rhythms,
highlighting importance in relation to human behaviour
Seasonal affective disorder (SAD, Infradian):
- Particular type of Infradian rhythm known as circannual rhythm
- Experience of SAD may be due to the disruption of the sleep/wake cycle due to the
prolonged periods of darkness in the winter
- Hypothesised that melatonin is implicated, pineal gland secretes melatonin until
dawn when there is an increase in light
- Winter = lack of light in morning = secretion process continues for longer which
affects production of serotonin (associated with depressive symptoms)
STUDY: TERMAN:
- Rate of SAD more common in Northern countries where the winter nights are longer
- Affects 10% of people in New Hampshire (North) but only 2% in Southern Florida
