What process does Czeisler’s study look at?
Cognitive processes
What was Czeisler’s aim?
To investigate if light exposure could help nightshirt workers adapt to daytime sleeping.
What are the negative effects of shift work?
- Sleep deprivation
- Mistakes at work
- Poor alertness
- Risk of heart disease
- Job stress
- Emotional problems
- Relationship breakdowns
What was Czeisler’s sample?
8 men aged between 22 and 29 who had never worked night shifts.
What was Czeisler’s method?
10 two week studies (5 control/5 treatment) were conducted. Temperature, physical activity and heart rate were recorded during a base week. Participants then did a week of night shifts, group 1 were exposed to bright light during the night shift and told to remain in the dark between 9am-5pm. Group 2 were exposed to ordinary room light during the shift and given no other instructions. Hourly cognitive performance tasks, mood and alertness assessments were carried out.
What measurements were used to asses Czeisler’s participants?
- Body temperature
- Blood samples
- Alertness (calculations test)
- Self report (alertness)
- Urinary excretion rate
- Cortisol concentration
What were the results of Czeisler’s study?
Participants exposed to bright light at night slept 2 hours longer than the second group. Experimental group had their circadian rhythm adjusted by 9 hours. Significant shift in lowest body temperature between week 1&2 and group 1&2.
What did Czeisler conclude?
Human circadian rhythm can be shifted by up to twelve hours by properly timed exposure to bright light in just three to four days.
What are strengths of Czeisler’s study?
- Multiple physiological measures to isolate cause and effect.
- Step toward the development of a
practical treatment for maladaptation to night time
work. - The difference between
the mean point of body temp of control group vs experimental group was huge and highly unlikely to have
occurred by chance.
What are weaknesses of Czeisler’s study?
- Small sample
- Only men
- Some variables not controlled
- Low ecological validity
- Self report = subjective
- Sleep disruption (noise during the day)
- Ethics = stress from loss of contact with friends and family.
What are analysis point of Czeisler’s study?
- Expected that we socialise, shop and work 24 hours a day = health implications, biological rhythms disrupted.
- Cortisol levels are at their lowest during the night so the immune system is less effective (people get ill).
- Effects of sleep deprivation.
- Train drivers miss warning signals on night shifts.
- 50% of traffic deaths happen at night.
- Industrial disasters often happen in early hours.
- Drivers are 3x more likely to be in a crash if fatigued.
What research links to Czeisler’s study?
- Gordon et al changed police officers from a backward shift rotation to a forward one and officers had 40% less accident and were more alert.
- Phillips et al found that when non-rotating shift work was introduced to Kentucky police officers the rate of sleeping at work lowered and there was fewer accidents.
- However permanent shifts can cause difficulty with social lives.
