THE EFFECT OF 40 HOURS OF CONSTANT WAKEFULNESS ON NUMBER COMPARISON PERFORMANCE

Abstract

We investigated the effects of sleep loss and circadian rhythm on number comparison performance. Magnitude comparison of single-digits is robustly characterized by a distance effect: Close numbers (e.g., 5 versus 6) produce longer reaction times than numbers further apart (e.g., 2 versus 8). This distance effect is assumed to reflect the difficulty of a comparison process based on an analogous representation of general magnitude. Twelve male participants were required to stay awake for 40 h in a quasi-constant-routine protocol. Response speed and accuracy deteriorated between 00:00 and 06:00 h but recovered afterwards during the next day, indicating a circadian rhythm of elementary cognitive function (i.e., attention and speed of mental processing). The symbolic distance effect, however, did not increase during the nighttime, indicating that neither cumulative sleep loss nor the circadian clock prolongs numerical comparison processes. The present findings provide first evidence for a relative insensitivity of symbolic magnitude processing against the temporal variation in energy state. (Author correspondence: [email protected])

Keywords:

• Attention
• Circadian rhythm
• Reaction time
• Sleep loss
• Symbolic distance effect

ACKNOWLEDGMENTS

This study is part of the Project “ClockWork” and financial support was provided by the Gottlieb-Daimler-and-Karl-Benz Foundation (www.daimler-benz-stiftung.de). Dr. Gordijn's work is supported by the 6th European IP EUCLOCK (No. 018741). We thank Claudia Renz for the determination of the melatonin concentration values, Andreas Häusler, Isabelle Jasper, Myriam Juda, Ildiko Meny, Sarah Postler, Kathrin Pusch, Jakub Späti, Claudia Renz, and Jessica Rosenberg for their assistance in conducting the study. We are grateful to Maan van de Werken and Marina Gimenez for their support in setting up the study in the Netherlands. Further we have to thank many people who provided helpful discussions on particular issues at the biannual ClockWork Meetings: Till Roenneberg, Anna Wirz-Justice, Martha Merrow, Simon Folkard, Christian Cajochen, Joachim Hermsdörfer, Serge Daan, Kurt Kräuchi, and Rainer Dietrich.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.