Disruption of biological rhythms
• Where our biological clock has become desynchronised from our external zeitgeber. Physiological cues (e.g. body temp, sleep/wake cycle) desynchronised from external cues (light, meal times).
• Examples - Jet lag and shift work
• Plane travel has become common but can be a problem when your biological clock tells you it is one time but local cues tell you it is another.
• EG: fly to New York from London, leave at midday, takes 7 hours. Arrive 7pm London time which is 2pm NY time. 4 hours later, your body says bed, NY time says party!
• = JET LAG
• Difficulty with concentration & attention
• Can last few hours or few days
• Worse travelling West to East, than East to West. No prob going N to S!
• East to West travel
• Our biological clock is ahead of local time and has to ‘wait’ for external cues to catch up.
• West to East travel
• Biological clock is behind local time and has to move forward to ‘catch up’.
• Phase advance seems to be harder to adjust to than phase delay.
How do we get over jet lag?
• Our SCN (influenced by light entering the eye) needs to adjust to the changed time in the new place.
• Can take several days
• Significant individual differences.
• Occasional travellers (e.g holiday makers) vs cabin crew studies.
– Recht et al (1995), followed baseball team for 3 yrs. They won 37% games when going W to E (phase advance) & 44% when going E to W (phase delay). This was statistically significant
– But lots of methodological problems (ability of different teams, fluctuations in form, injury). So low validity.
– Support from American servicemen study – more jet lag when going from Europe to USA (3 days), than USA to Europe (8 days).
Cabin crew studies = Regular exposure
• Found to have raised levels of stress hormones & do less…