Effect of Stress and Glucose on Self-Control Mary Redding and H. Anna Han, PhD

1. Effect of Stress and Glucose on Self-Control Mary Redding and H. Anna Han, PhD Department of Psychology, St. Mary’s College of Maryland Results Introduction • Self-control is the effortful process of refraining from behaviors that may be initially rewarding, but have long-term costs.1,2,6 • Ego Depletion explains that a person’s self-control depends on a limited cognitive resource, which can be depleted after use. 1,2,3,4,6 • Stress is a factor that can contribute to self-control failures by consuming the resource required for self-control. 5,6 • Controlled mental processes (such as self-control) require more glucose than automatic processes.3 • Specifically, an increase in blood glucose levels resulted in fewer self-control errors after an initial ego depletion task. 3,4 • Present Research • Further examined the depleting effect of stress as well as the attenuating role of glucose on self-control. • 2 (stress/no stress) x 2 (glucose/ no glucose) design • Reaction times (RT) on the Stroop task was calculated by subtracting the average RT on the congruent trials from the incongruent. • ANOVA showed there was no main effect of stress on self-control F < 1, nor main effect of glucose on self-control, F < 1. Moreover, there was no interaction between stress and glucose F < 1. • By removing the outliers (data with z-scores >4 and <-4) from the data set (n=53), there was no significant main effect of either stress on self-control, F < 1, or glucose on self-control, F < 1. Hypotheses • Participants under stress would have worse self-control performance (slower Stroop RT) compared to those not under stress. • Participants who receive sugar will have better self-control performance (faster Stroop RT) than those who do not. • Stress + no sugar=worst self-control • No stress + sugar= best self-control. Methods • Participants • 58 (45 female, 13 male) students from St. Mary’s College of Maryland. • Students were excluded from participation if they had medical conditions related to sugar or sugar substitutes, such as diabetes. • Procedures • Participants randomly assigned a condition by session. • Participants in the stressful conditions had 4 minutes to complete a solvable anagram task5, while those in the non-stressful conditions had 15 minutes to complete the same task. • After competing the anagrams, the participants in the glucose conditions received regular “Life Savers” brand candy with sugar, and those in the no glucose conditions received sugar-free version. • While participants ate the piece of candy, all participants answered 3 filler questionnaires (were not analyzed) which on average took about 10 minutes (the time to metabolize the sugar). • Self-control was measured by reaction times (RT) on a computerized Stroop task, which randomly presented 16 congruent trials and 16 incongruent trials of a color/word pairing to the participants. • At the end of the study, participants answered the questions from the 10-item Perceived Stress Scale. Conclusions • Results failed to support previous research that stress has detrimental effects on self-control and that glucose would have attenuating effects on self-control. • Limitations • Anagram task as a stress-inducer: The anagrams may have been equally stressful because both stressed and non-stressed conditions had relatively high perceived stress scale scores which were not significantly different between the two conditions. • Form of glucose: One piece of candy may not have been enough to produce an effect (previous studies used 8-oz. glass of sugar water). Also, it may take more than 10 minutes to metabolize the sugar. • Measure of self-control: The Stroop task is normally used in cognitive studies on selective attention, cognitive flexibility or processing speed, for example. • Future Research: • Continue to use anagrams to induce stress, but have a control condition where participants are acclimated to the lab setting and/or an activity that does not require controlled mental processing (i.e. reading a magazine). • Use a larger or more efficient amount of sugar than the one piece of Life Savers’ candy. * References • Baumeister, R. F., Vohs, K. D., & Tice, D. M. (2007). The strength model of self-control. Current Directions in Psychological Science, 16(6), 351-355. • Baumeister, R. F., Bratslavsky, E., Muraven, M., & Tice, D. M. (1998). Ego depletion: Is the active self a limited resource? Journal of Personality and Social Psychology, 74(5), 1252-1265. • Gailliot, M. T., Baumeister, R. F., DeWall, C. N., Maner, J. K., Plant, E. A., Tice, D. M., et al. (2007). Self-control relies on glucose as a limited energy source: Willpower is more than a metaphor. Journal of Personality and Social Psychology, 92(2), 325-336. • Masicampo, E. J., & Baumeister, R. F. (2008). Toward a physiology of dual-process reasoning and judgment: Lemonade, willpower, and expensive rule-based analysis. Psychological Science, 19(3), 255-260. • Mayzner, M. S., & Tresselt, M. E. (1966). Anagram solution times: A function of multiple-solution anagrams. Journal of Experimental Psychology, 71(1), 66-73. • Oaten, M., & Cheng, K. (2005). Academic examination stress impairs self-control. Journal of Social and Clinical Psychology, 24(2), 254-279. • Tice, D. M., & Baumeister, R. F. (1997). Longitudinal study of procrastination, performance, stress, and health: The costs and benefits of dawdling. Psychological Science, 8, 454-45. Acknowledgements Special thanks to Dr. Anna H. Han and Angela Draheim for all their help and support.