Performance may predict natural killer cell activity after an acute time-limited stressor

Much attention has been given to natural killer cell activity (NKCA) in acute stressor research. While many studies show that acute stressors increase NKCA, fewer studies have investigated the variability in NKCA within an experimental group that is associated with performance. In his ‘Toughness’ theory of arousal, Richard Dienstbier suggests that behavioural performance during an acute stressor task could account for a variability in NKCA. We were not aware of any human studies that had investigated this possibility. Thus, in the present study we tested Dienstbier's proposal in a group of male and female human participants (n = 25) who completed a 4‐min serial subtraction mental arithmetic task. Blood samples were taken before and after the task. Controlling for baseline NKCA, performance score significantly predicted post‐task NKCA, β = 0.455, p = 0.01, and accounted for 25 per cent of the variance. Coincidence test showed no significant difference between men and women in predicting post‐task NKCA on performance score. Thus, in addition to evidence in the animal literature, the present study provides evidence that performance on an acute stressor is associated with enhanced NKCA in humans. Copyright © 2007 John Wiley & Sons, Ltd.