ultraradian rhythm

• -individual differences in sleep cycle. sleep scientists observed sws reduces with age. growth hormone produced during sws decrease as age. cauter 2000 suggested resulting sleep deficit may explain various issues with old people such as alertness.l to increase sws old ppl should practise relaxation. individual differences help expand understanding of sleep and led to many practical applications
• -individual differences. tucker 2001 found large differences between pps in terms of the differences of duration of each sleep stage mainly 3 and 4 suggesting these differences are likely to be biologically determined. taking these findings into consideration must be cautious when generalising results of the research to the wider population, as simplistic conclusions lack validity
• sleep studies tend to be carried out in a highly controlled lab allowing for a high level of experimental control over potential confounding variables. e.g ecgs are used to measure brain wave activity for an accurate sleep report, as self report is open to bias. also allows researcher to control caffiene intake and mobile phone usage. could argue that an ecg acts as a confounding variable as it requires a skull cap which may disrupt sleep, also ecg can be noisy and the noise may be difficult to eliminate
• stage 1 and 2:

  easily woken high frequency low amplitude. alpha waves random changes can occur in stage 2
• stage 3 and 4:

  deep sleep or slow wake sleep . low frequency and high amplitude. delta waves. difficult to wake
• stage 5:

  rem sleep = rapid eye movement. closely resembles awake brain. produces theta waves. eye occassionly move. dreams occur