title: The effects of high altitude on choice reaction time mean and intra-individual variability: Results of the Edinburgh Altitude Research Expedition of 2008.
abstract: OBJECTIVE
  This study aimed to investigate the effects of high altitude on reaction time (RT) mean and intra-individual variability.
  
  
  METHODS
  Ten students (6 men, 4 women) took a 4-choice RT test and had their vital signs and Lake Louise (LL) score measured on 21 occasions during the Edinburgh Altitude Research Expedition of 2008 to the Western Himalayas (max. altitude 5,565 m).
  
  
  RESULTS
  Linear mixed modeling revealed that mean RT was significantly impaired at altitudes above 4,000 m (p < .001), but relatively unaffected below that threshold. An estimated increase in RT between 4,000 and 5,000 m was 15.5 ms, 95% CI [11.1, 19.9]. LL score was related to slower RTs (B = 1.97, 95% CI [0.70, 3.23], p < .01), while number of errors was associated with faster RTs (B = -1.50, 95% CI [-2.60, -0.39], p < .01). There were persistent practice effects in mean RT (B = -2.16, 95% CI [-2.49, -1.83], p < .001. Log-transformed intra-individual variability in RT increased with higher LL scores (B = 0.01801, 95% CI [0.0049, 0.0311], p < .01) and decreased with rising temperature (B = -0.00754, 95% CI [-0.0119, -0.0032], p < .001). However, after controlling for mean RT, these effects were no longer significant.
  
  
  CONCLUSIONS
  RTs become significantly impaired above a threshold of 4,000 m. Altitude-related changes in RT intra-individual variability were accounted for by mean RT.
authors.affiliation: Centre for Cognitive Ageing and Cognitive Epidemiology, Department of Psychology, University of Edinburgh, Scotland.
authors.forename: Dominika
authors.initials: D
authors.lastname: Dykiert
authors.forename: David
authors.initials: D
authors.lastname: Hall
authors.forename: Nikki
authors.initials: N
authors.lastname: van Gemeren
authors.forename: Richard
authors.initials: R
authors.lastname: Benson
authors.forename: Geoff
authors.initials: G
authors.lastname: Der
authors.forename: John M
authors.initials: JM
authors.lastname: Starr
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Deary
mesh_terms: D000531:Altitude; D001831:Body Temperature; D002755:Choice Behavior / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D007206:Individuality; D008297:Male; D010100:Oxygen / Q000097:blood; D011930:Reaction Time / Q000502:physiology*; D015656:Respiratory Mechanics / Q000502:physiology; D013696:Temperature; D013997:Time Factors; D055815:Young Adult
chemical_list: D010100:Oxygen