Describe the definition of a 

Circadian Rhythm?

Rhythms lasting 24 hours (ie. consistent).

Cyclical Changes in the system.

Examples are the sleep wake cycle and core body temp.

What is an Endogenous Pacemaker?

An internal body clock.

What is are Exogenous Zeitgebers?

External cues from the environment (eg. light, food, noise).

What is the Sleep-wake Cycle?

A circadian endogenous pacemaker which regulates when we sleep and when we wake up. There are also exogenous cues which can have an effect on this internal clock to help us adjust to different environments.

Name 2 Psychologists who studied the Sleep-wake cycle?

Michel Siffre

Folkard et al.

Describe Michel Siffre's study into the

Sleep-wake cycle?

Siffre was an underground cave explorer. In his study, he spent long periods of time underground with no external cues as to the time, and simply ate and slept when he felt like it. His findings supported the existance of an endogenous clock as his free-running cycle settled to a regular rhythm just over 24 hours.

Describe Folkard et al.'s study into the

Sleep-wake cycle?

Aimed to see if external cues could override the interal clock. Participants lived in a cave where they were isolated from any external cues such as sunlight and were told to go to bed at 11:45pm and wake up at 7:45 when the clock said so. Folkard secretly sped the clock up so that it said 24 hours had passed when only 22 had. Despite this, the participants' rhythms did not change from the one they had settled to. This suggests that the rhythm can only be guided to a certain extent by external cues.

Briefly describe

Core-body temperature?

Our temperature is usually lowest at 4:30am and highest at 6:00pm. We can predict consistent body temperatures throughout the day as it is a circadian rhythm.

Briefly describe the rhythm of

Hormones?

2 main examples of hormones which follow circadian rhythms are melatonin and growth hormones. Cortisol is lowest after midnight which is why we have difficulty concentrating after that time.

Name 2 Psychologists who support the

Sleep-wake cycle and core body temperature?

(Initials: A&W, F)

Aschoff & Wever

Folkard et al.

Why do Aschoff & Wever support the 

Sleep-wake cycle?

Placed participants in an underground WWII bunker without any external cues. Findings showed that the rhythms settled to around 24-25 hours, supporting Siffre's study.

Why does Folkard et al. support the

Core body temperature?

Aimed to test the learning ability of 12-13 year olds and so had stories read to them at either 9:00am or 3:00pm. Findings showed that the afternoon group, with the highest body temperature, showed superior recall.

Name a Psychologist criticising the Sleep-wake cycle

and 2 IDA points?

(D, D, CSV)

Duffy et al.

Determinist

Case Study Validity

Why does Duffy et al. criticise the

Sleep wake cycle?

Individual differences. Some people prefer to get up early and go to sleep early, whereas others prefer to get up late and sleep late. Our own personal preferences have some effect.

Why might the Sleep-wake cycle be criticised as

Determinist?

Suggests rhythms are fixed by internal mechanisms but does not consider our own willingness. We may choose to go to sleep 2 hours early but still get up at the same usual time, without difficulty.

Why might Siffre's study lack some

Validity?

It is a case study which means it is based upon one person - himself. Therefore, his behaviour may not be a true representation of everyone else's. He may have also been affected by the cold temperature of the cave which was an uncontrolled variable. However, other above ground studies have still supported Siffre's findings, such as Folkard et al.