Evaluating Memory in Stress Induced Situations: Differences in Stress Levels and Gender

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Methods

Participants. The sample used for this study consisted of 71 University of Guelph students aged 18-24 from various academic programs. The participants were asked to indicate their gender and participated in an experimental and control condition as this study used a within-subjects design. All participants were instructed to review and sign an informed consent form prior to participation in the experiment and were told that they were able to withdraw from the study at any time. The participants were awarded with candy upon completion of the study. Participants were tested in various study rooms in the McLaughlin Library on the University of Guelph Campus; 50 Stone Road East. Participants were recruited via social networking and word of mouth recruiting.

Design. The collected data was analyzed using two separate 2x2 mixed factorial designs in SPSS to determine if there were any statistical differences between any of the experimental conditions. Participant’s scores on the working memory task were recorded on a piece of paper through written recall. Participant’s stress levels were measured using a self-report Likert scale at the beginning and the end of the experiment. The results of this study will display if there are any differences in performance on a working memory task between the neutral condition and the stress condition and if there were any differences in stress levels before and after completing the experiment.

Materials. Testing for this study took place in various study rooms in the McLaughlin Library on the University of Guelph Campus based on availability. Materials included an informed consent form, two versions of a ten word list, two Likert scales, a piece of paper to record the participants written recall of the words, and a writing utensil.

Procedure. Participants were asked to sit in a chair at a table facing two researchers. The researchers described the study to them, and they were asked to read over and sign an informed consent form. To measure overall mood and stress levels participants then completed a Likert Scale. Participants then began the first test of working memory. The test required them to look over a list of ten words for thirty seconds, take a thirty second break and then try to recall as many words as possible in any order on a piece of paper. Upon completion participants began the variation of the Trier Social Stress Test. They were instructed to talk about grass for two minutes without any preparation or interruption from the researchers until the time was complete. If the participant stopped they were instructed to continue. Once their presentation was complete they were instructed to count down from 507 by multiples of 13 for a total of two minutes. If they made a mistake they were instructed to start from the beginning. When they finished the stress test they were required to look at a different list of ten words for thirty seconds, take a thirty second break and then recall as many words as they could in any order on a piece of paper. Finally participants were instructed to fill out an identical Likert Scale to the one completed at the beginning of the experiment to measure overall mood and stress levels. Upon completion the participants were debriefed and given the choice of a variety of candy.

Results

Effects of stress condition (Test1 = neutral, and Test2 = stressed) and gender (male or female) on performance on a working memory task were examined using a 2x2 mixed factorial design. The stress condition was the within-subjects independent variable, gender was the between-subjects independent variable, and performance on the working-memory task was the dependent variable. The four conditions were as follows, Test1 Female (M = 6.70, SD = 1.84), Test1 Male (M = 6.85, SD = 1.79), Test2 Female (M = 7.08, SD = 1.89), and Test2 Male (M = 7.09, SD = 1.66). The dependent variable was measured through a working-memory task, first for the neutral condition, and then again for the stress condition. A higher score indicates higher performance on the working-memory task. All tests of significance were run at an alpha level of p = .05. The ANOVA homogeneity of variance assumption was not violated for Test1, Levene’s F(1, 69) = .06, p = .80, or for Test2, Levene’s F(1, 69) = .78, p = .38. As shown in Figure 1, there was no significant main effects of stress condition F(1, 69) = 2.73, MSE = 1.22, p = .10, η2 = .04, and no significant main effect of gender F(1, 69) = .04, MSE = 5.26, p = .84, η2 on performance on the working-memory task. Partial eta squared showed a small effect size for both main effects according to Cohen’s (1988) standards. The interaction between condition and gender also proved to be insignificant F(1, 69) = .15, MSE = 1.22, p = .70, η2

Effects of time (Test1 = score before, and Test2 = score after) and gender (male or female) on overall stress levels were examined using a second 2x2 mixed factorial design. The time of data collection was the within-subjects independent variable, gender was the between subjects variable and overall stress levels was the dependent variable. The four conditions were as follows, Test1 Females (M = 5.30, SD = 1.93), Test1 Males (M = 4.62, SD = 2.24), Test2 Females (M = 6.11, SD = 2.00), and Test2 Males (M = 5.76, SD = 1.95). The dependent variable was measured using a self-report Likert Scale at the beginning of the study and then again at the end of the study. A higher score indicates a higher stress level. All tests of significance were run at an alpha level of p = .05. The ANOVA homogeneity of variance assumption was not violated for Test1, Levene’s F(1, 69) = 1.30, p = .26, or for Test2, Levene’s F(1, 69) = .001, p = .97. As shown in Figure 2 there was a significant main effect of time F(1, 69) = 41.30, MSE = .83, p η2 = .37 and no significant main effect for gender F(1, 69) = 1.25, MSE = 7.43, p = .27, η2 = .02. The significant main effect indicates that participants were significantly more stressed after completing the Trier Social Stress Test. Partial eta squared showed a small-medium effect size for the main effect of time and a small effect size for the main effect for gender according to Cohen’s (1988) standards. The interaction between time and gender was also insignificant F(1, 69) = 1.21, MSE = .83, p = .28, η2 = .02. Partial eta squared showed the interaction had a small effect size according to Cohen’s (1988) standards.

Discussion

The purpose of this study was to examine the effects of stress on performance in working-memory related tasks in both males and females. It was hypothesized that stress would have an effect on working memory, that stress would have a stronger effect on men than