Participants and Recruitment

Thirty participants will be recruited from within the Virginia Military Institute summer student body. Students must be 18 years or older to participate. Researchers (i.e., principal investigator and/or faculty advisor) will pre-screen participants for colorblindness. Individuals who report colorblindness will not be eligible to participate due to the nature of the experimental task (i.e., Stroop color-word test). Researchers will also pre-screen participants to ensure their health is such that they are able to engage in strenuous physical exercise (i.e., running on a treadmill). Participants who have a medical condition that prevents them from engaging in physical exercise will not be eligible to participate.

Researchers will recruit the participation of students attending VMI summer school, summer undergraduate researchers, and VMI Summer Transition Program (STP) students. Participants will be recruited through e-mail, posted notices, and/or in-person visits to classes. Researchers will send e-mails to course instructors requesting that they announce the study in their classes. Researchers may also send e-mails directly students enrolled in summer courses. Participants may receive extra credit for participating in the experiment from their course instructors. Course instructors will decide whether or not to offer extra credit to students who choose to participate in this experiment.

Independent Variables

Participants’ performance on a behavioral measure of self-control will be compared across two groups: (1) a physical-exertion group in which participants will engage in physical exercise, and (2) a control group in which participants will not engage in physical exercise. Participants assigned to the physical-exertion group will jog on a treadmill for 20 minutes at 70% of their predicted maximum heart rate. Participants in the control group will not run on the treadmill and will instead sit and watch a relaxing video for the 27 minutes.

Dependent Measures

Stroop color-word task. The proposed research will use participants’ performance on the Stroop color-word task (Stroop, 1935) as a behavioral measure of self-control. The Stroop task is a commonly used method for measuring self-control (Gailliot et al., 2007). In order to perform the task, participants will be presented with color-words (e.g., “purple”) on index cards printed in a mismatched colored font (e.g., the word “purple” written in red font). Rather than reading the word, participants will be asked to state the font color. For example, the word “purple” may be presented in red font and the participant must respond “red.”

The total time to state the correct font colors on all cards and the number of errors made will be measured with the assumption that the longer the response time and the more errors, the lower the individual’s self-control.

Response time. The sessions will be audio recorded using the Voice Memos application on the iPhone 6. The Voice Memos application records time in seconds, so it will be used as the measurement device to record response time to complete the Stroop task. Response time is defined as the amount of time between the presentation of the first index card until the participant correctly responds to the last index card and the researcher stops the timer. Response time will be measured in seconds and the average response time per trial will be calculated using the following formula:

Seconds to complete Stroop task

Number of trials

Errors. If a participant makes an error during the Stroop task the researcher will say “error.” After the session, a researcher will listen to the audio recording and tally the errors made. An error is defined as the participant fully stating an incorrect font color on a given trial one or more times. The average number of errors per trial will be calculated using the following formula:

Number of errors in Stroop task

Number of trials