key study: czeisler et al (1990)

Question 1

aim

Answer 1

to research if exposure to bright light at night and darkness in day can treat maladaptation due to night work

Question 2

participants

Answer 2

8 healthy men aged 22-29 years old, none of the participants had worked regularly on night shifts before, they had no sleep disorders, none were jet lagged within the previous 6 weeks, they were asked to abstain from recreational drugs, alcohol, and caffeine during the study

Question 3

method

Answer 3

2 week experiment with 5 control conditions and 5 treatment conditions. 1st week baseline study, 2nd week night shift work. men lived at home but reported for ‘work’ at the laboratory each night in the second week, two men (1 control 1 treatment) did not conform to the protocol so results were excluded. a technician monitored the subjects to make sure they stayed awake, the control group worked during the night in ordinary indoor lights of about 150 lux. the experimental group worked under bright lights of 10000 lux, equivalent to early morning light and asked to stay in complete darkness from 9am to 5pm. controls had no specific instructions, all completed cognitive-performance tasks hourly, but were otherwise free to do their own work

Question 4

measurements

Answer 4

body temperature at 1 minute. alertness was assessed 3 times an hour using a calculations test. urinary excretion rates. blood samples were collected every 15-25 minutes on a randomised schedule. subjective alertness (asking them). plasma cortisol concentration

Question 5

results

Answer 5

treatments study slept for 2 hours longer than control, shift in body temperature between week 1 and 2 between control and treatment, same behaviour but shown an hour later in treatment, the treatment were more alert by the end of week 2

Question 6

conclusion

Answer 6

maladaptation to night shift work can be treated with properly timed exposure to bright light during night shift work and darkness during daytime sleep

Question 7

evaluations: strengths

Answer 7

robust testing methods (validity), real world applications, extraneous variables, ecological validity (field experiment)

Question 8

evaluations: weaknesses

Answer 8

limited sample, ethical breach (stress), some variables not controlled