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

Department of Psychology, St. Mary’s College of Maryland

References

Conclusions

ResultsIntroduction

Methods

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AcknowledgementsSpecial thanks to Dr. Anna H. Han and Angela Draheim for all their help and support.

• 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

1. 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.

2. 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.

3. 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.

4. 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.

5. Mayzner, M. S., & Tresselt, M. E. (1966). Anagram solution times: A function of multiple-solution anagrams. Journal of Experimental Psychology, 71(1), 66-73.

6. Oaten, M., & Cheng, K. (2005). Academic examination stress impairs self-control. Journal of Social and Clinical Psychology, 24(2), 254-279.

7. 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.

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.

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.

Congruent IncongruentRed RedBlue Blue

Yellow YellowGreen Green

• 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.

• 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.

Stress No stress0

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Mea

n RT

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Figure 1. The mean Stroop RT scores in each condition excluding outliers. Error bars represent 1 standard error of the mean.