Edited by: Florin Dolcos, University of Illinois Urbana-Champaign, USA
Reviewed by: Oliver T. Wolf, Ruhr University Bochum, Germany; Shaozheng Qin, Stanford University, USA; Marloes J. A. G. Henckens, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands
*Correspondence: Roselinde K. Henderson, Department of Psychology and Neuroscience, University of Colorado at Boulder, 345 USB, Boulder, CO 80309, USA. e-mail:
This article was submitted to Frontiers in Emotion Science, a specialty of Frontiers in Psychology.
This is an open-access article distributed under the terms of the
The ability to engage in goal-directed behavior despite exposure to stress is critical to resilience. Questions of how stress can impair or improve behavioral functioning are important in diverse settings, from athletic competitions to academic testing. Previous research suggests that controllability is a key factor in the impact of stress on behavior: learning how to control stressors buffers people from the negative effects of stress on subsequent cognitively demanding tasks. In addition, research suggests that the impact of stress on cognitive functioning depends on an individual’s response to stressors: moderate responses to stress can lead to improved performance while extreme (high or low) responses can lead to impaired performance. The present studies tested the hypothesis that (1) learning to behaviorally control stressors leads to improved performance on a test of general executive functioning, the color-word Stroop, and that (2) this improvement emerges specifically for people who report moderate (subjective) responses to stress. Experiment 1: Stroop performance, measured before and after a stress manipulation, was compared across groups of undergraduate participants (
Stress is part of life. Pursuing goals despite exposure to stressors, or better yet, showing enhanced functioning in response to stress, are abilities that are fundamental to survival and resilience (Maier and Watkins,
The effects of stress on cognitive functions, specifically, may mediate the helpful and harmful effects of stress in complex domains such as those described above. Stress research with humans has yielded evidence for both positive and negative effects of stress and stress hormones on cognitive functions (Lupien et al.,
One possibility is that these research endeavors have often focused on group differences (e.g., stress group versus no-stress group) without examining individual differences in response to those stressors (either subjective stress response or physiological reactivity). When researchers have monitored physiological reactivity to stress, several studies have found that cortisol and performance on working memory tasks are negatively correlated (Qin et al.,
Controllability of stressors is also a key factor that influences how stress affects behavioral performance (Dickerson and Kemeny,
Thus, controllability of, and individual responses to, stressors influence the effects of stress exposure on cognitive and behavioral functioning. However, several intriguing questions about the nature of these effects remain unexplored. First, the question of what types of stress exposure can enhance cognitive functioning remains only partially resolved. While some promising evidence suggests that exposure to moderately intense stress predicts improved working memory performance, the dearth of research on individual differences, and inconsistencies in group-level effects, make this association far from conclusive. Furthermore, the question remains open whether exposure to controllable stress can enhance behavioral functioning. A number of studies documented the impairing effects of uncontrollable stress, but failed to find any benefit of exposure to controllable stress (Hiroto,
Second, although controllability of stress and individual differences in stress response have been investigated separately, little research has examined the interaction of these factors. One research study showed that participants who appraised stressors as challenging performed better on an active coping task than participants who appraised the same stressors as threatening (Tomaka et al.,
Third, our understanding of the cognitive abilities affected by stress controllability and level of stress response remains imprecise. Although both human and animal research suggests that the effects of controllability on cognitive function are mediated by underlying systems fundamental to learning (Maier and Watkins,
Most of the research investigating effects of stress intensity or reactivity has focused on working memory ability. However, it is not known whether stress specifically affects working memory, or EF more broadly. EFs are best characterized as separable but related cognitive processes, with both unique and shared individual differences, genetic influences, and neural substrates (e.g., Miyake et al.,
To explore common EF processes in the current research, we administered the “gold standard” of EF tasks (MacLeod,
In sum, the current research investigated the helpful or harmful effects of stress on common EF, as assessed by the Stroop task. Specifically, this research explored the (linear or quadratic) relationship between individual differences in stress response and Stroop performance, and whether these effects depend on controllability of stress exposure.
This study tested the hypothesis that controllability of stress, and individual differences in subjective stress, are factors that interact to affect EF. Our stress manipulation included two sources of psychological stress to which participants were exposed while performing a choice-RT task: social-evaluative stress in the form of performance pressure, and sensory stress in the form of noise exposure.
Previous research has shown that uncontrollable, social-evaluative stress is the most potent form of psychological stress (Dickerson and Kemeny,
As a result of the above considerations, we manipulated stress exposure between groups in the following manner. In our controllable stress condition (CSt), participants received accurate, feedback regarding their performance (fast responses elicited success feedback), and could learn to control the duration of noise stressors by responding quickly to stimuli. In our uncontrollable stress condition (USt), participants were exposed to two sources of uncontrollability. First, the type of noise and nature of performance feedback received for each trial were not contingent on responses. This non-contingency made it impossible for these participants to learn how to control the duration of the noise stress or reliably predict success versus failure feedback. Second, people in this group received a higher proportion of (inaccurate) failure feedback. This biased performance feedback suggested to participants that their responses were, overall, not fast enough to successfully perform the task. Importantly, the CSt and USt groups did not differ on noise exposure, task stimuli, or response requirements. Finally, we included a third, no-stress condition (NSt), in which people were required to respond to identical stimuli as the other two groups, but received no performance feedback or noise exposure.
In this study, participants completed the Stroop task at the beginning of the research session to assess their baseline ability to exert general EF. After completing one of the three stress task conditions described above, participants completed the Stroop task a second time. This design allowed us to control for baseline differences in EF by examining changes in Stroop performance from pre- to post-stress exposure.
Participants were 109 undergraduate volunteers ages 18–24 from introductory psychology courses at the University of Colorado Boulder (Table
Condition | Sample |
Self-report |
Cognitive tasks |
||||
---|---|---|---|---|---|---|---|
Subjective stress |
Subjective control |
BDI score |
Pre-stress Stroop interference |
Post-stress Stroop interference |
Change in interference |
||
CSt | 42 (29) | 17.07 (4.67) | 6.71 (1.47) | 11.51 (6.54) | 0.0119 (0.0101) | 0.0074 (0.0094) | −0.0045 (0.0108) |
USt | 41 (24) | 19.02 (4.43) | 4.32 (1.84) | 9.73 (6.86) | 0.0107 (0.0103) | 0.0096 (0.0090) | −0.0011 (0.0106) |
NSt | 26 (10) | 14.56 (5.28) | n/a | 8.65 (8.20) | 0.0132 (0.0110) | 0.0106 (0.0091) | −0.0026 (0.0101) |
Total | 109 (63) | 17.16 (5.00) | 5.53 (2.04) | 10.15 (7.11) | 0.0118 (0.0103) | 0.0090 (0.0092) | −0.0027 (0.0106) |
Participants were informed of the study procedures at the beginning of the research session, provided written consent, and were randomly assigned to one of the three stress conditions (USt,
Task or measure | Time (minute) |
---|---|
Rating of state affect (PANAS-X) | 2 |
Assess baseline general executive functioning (color-word Stroop) | 5 |
Stress manipulation | 16 |
Assess post-stress general executive functioning (color-word Stroop) | 5 |
Rating of state affect (PANAS-X) | 2 |
Rating of subjective stress, control | 2 |
Report depression (BDI-II) | 5 |
Total | 37 |
A computer system captured accuracy and reaction time (RT) via millisecond-accurate keyboard press for all trials. Participants assigned to stress conditions that included an auditory stressor (either 2000 or 4000 ms in duration) listened to stimuli through headphones, with volume calibrated at 72–80 dB.
On each trial of the Stroop task a word written in one of four ink colors (green, yellow, red, or blue) appeared in the center of the screen for 2000 ms and participants identified the ink color as quickly as possible by hitting the corresponding button on the keyboard. Prior to beginning the first Stroop task, participants were given 16 practice trials in which XXXX stimuli were presented to familiarize the participant with the task demands and location of the response keys for each of the four colors. During the task, trials were presented in two blocks (48 trials each; 38% incongruent and 62% neutral across blocks). Incongruent words feature conflict between ink color and word meaning (e.g.,
Participants performed a choice-RT task and either were (USt and CSt groups) or were not (NSt group) exposed to concurrent psychological stress. The choice-RT task required participants to choose behavioral responses based on perceptual features in the display (Figure
For each trial, an arrow pointing either left or right appeared inside a white fixation box on the computer monitor. Participants responded to the direction of the arrow as quickly as possible by pressing the corresponding button on the keyboard. All participants completed a practice block (20 trials) without any stress exposure, to familiarize themselves with the choice-RT task.
In the two testing blocks (80 trials each), participants in the CSt and USt groups had two performance goals: (1) to respond accurately and fast enough to beat a challenging time limit, for which they received performance feedback indicating success (yellow fixation box) or failure (blue fixation box; blocks 1 and 2); and (2) to learn how their responses controlled the duration of a noise stressor that was evoked by each response (block 2 only). Participants in the NSt condition completed the same task, but with no feedback or noise stress. This task was based on classic manipulations of instrumental control in which participants must learn how to control a noise by pushing a sequence of buttons (Hiroto,
For the CSt group, feedback and noise exposures were controllable: fast, accurate responses elicited short noises accompanied by success feedback, while slow or inaccurate responses elicited long noises coupled with failure feedback. A moving-window for response speed ensured that every participant was able to beat the time limits on 80% of trials, and participants received success feedback and short noises on these trials. When participants failed to beat the time limit (20% of trials) they received failure feedback and long noises.
For the USt group, feedback and noise exposures were uncontrollable, both (1) because feedback and noises were not contingent on response speed, and (2) because feedback was biased to indicate a higher rate of failure (blue fixation box for 50% of trials, regardless of response speed or accuracy). The CSt and USt groups were matched on their true response success and noise exposure: as in the CSt group, a moving-window for response speed ensured that every participant was actually able to beat the time limits on 80% of trials, and every participant received a short noise on 80% of trials. However, unlike the CSt group, the USt participants received non-contingent performance feedback that was biased for failure (success feedback for only 50% of trials) and short and long noises were random and unrelated to their response speed or performance feedback
Finally, for the NSt group, participants received no performance feedback (green fixation box after every response, regardless of response accuracy or speed) and were not exposed to noise (Figure
At the end of testing, participants reported subjective ratings of stress to provide a measure of individual differences in response to the stress exposure. Participants rated the following on a 1 (low) to 9 (high) scale: (1) level of stressfulness of the noise exposures (CSt and USt only), (2) level of stressfulness of the task (choice-RT) demands, (3) degree to which you believe someone else would have performed better than you (social comparison), (4) degree to which you believe you performed well on the task. The scores for these scales were summed to yield a composite score of subjective stress for each participant. Because they did not rate the noise exposure item, scores for participants in the NSt condition were multiplied by 4/3 to make this group comparable to the CSt and USt groups. Across the sample, scores were mean-deviated for the purpose of regression analyses.
Self-reported perception of control was also assessed at the end of testing, with ratings reported from 1 (low) to 9 (high). This measure was collected to confirm that our manipulation of controllability was successful in eliciting differences between groups.
We used well-validated measures of current depression and state affect to confirm that groups were equivalent on these dimensions at baseline, and to investigate whether participants experienced changes in affect over the course of testing.
Participants reported level of depression in the past two weeks using the BDI-II (Beck et al.,
In addition, they completed the Positive and Negative Affect Questionnaire (PANAS-X; Watson and Clark,
For the Stroop tasks, RT analyses were conducted by calculating an average for each trial type. Incorrect trials and trials on which RTs were less than 200 ms or exceeded 3 standard deviations above the within-subject mean were excluded from analyses. RTs were natural log transformed to reduce the skew common to RT data and which violates the statistical assumption of normal distribution necessary for analysis. Accuracy analyses were conducted by calculating the total correct for each trial type pre- and post-stress manipulation.
Data were analyzed with multiple-regression analyses. For group comparisons, two orthogonal contrast-coded predictors were entered in the regression model: controllability (CSt = 1, USt = −1, NSt = 0) and stress exposure (CSt = −1, USt = −1, NSt = 2). For group by subjective stress response (linear or quadratic) interactions, these contrast codes were multiplied by the subjective stress score (controllability × subjective stress and stress exposure × subjective stress) or square [controllability × (subjective stress)2 and stress exposure × (subjective stress)2].
Outlier detection was accomplished in two ways: (1) observations on self-report measures that exceeded 3 standard deviations above or below the group mean were excluded from analyses; (2) for any significant regression effects, standardized df beta was calculated to detect observations that had undue influence on the analysis according to the standard threshold (df beta > 2/(√
As a manipulation check, we compared self-reported perceived control between the CSt and USt groups (note: members of the NSt group did not rate this item, as they were not asked to learn to control outcomes). Confirming that the controllability manipulation was effective, the CSt group (
We conducted analyses to examine whether our stress manipulation affected subjective ratings of stress. Including sex as a covariate revealed a significant difference in subjective stress responses between men and women, across groups; women reported higher stress (
Finally, because subjects in the uncontrollable stress group received a higher rate of failure feedback, we might expect their performance ratings to be more negative than the ratings of subjects in the other groups. This is reflected in their slightly higher composite ratings of subjective stress (see Table
We conducted a regression predicting changes in Stroop interference by the following: group contrast codes (controllability and stress exposure), the linear effect of subjective stress, the quadratic effect of subjective stress, and interactions between group predictors and stress response effects (Table
Source | SS | df | MS | |||
---|---|---|---|---|---|---|
Model | 0.002 | 8 | 0.000 | 1.817 | 0.083 | 0.129 |
(Constant) | 0.001 | 1 | 0.001 | 12.222 | 0.001 | 0.111 |
Controllability | 0.001 | 1 | 0.001 | 7.762 | 0.006 | 0.073 |
Stress exposure | 0.000 | 1 | 0.000 | 0.209 | 0.648 | 0.002 |
Subjective stress | 0.000 | 1 | 0.000 | 1.664 | 0.200 | 0.017 |
Subjective stress2 | 0.001 | 1 | 0.001 | 5.327 | 0.023 | 0.052 |
Controllability × subjective stress | 0.000 | 1 | 0.000 | 0.015 | 0.903 | 0.000 |
Stress exposure × subjective stress | 0.000 | 1 | 0.000 | 0.808 | 0.371 | 0.008 |
Controllability × subjective stress2 | 0.001 | 1 | 0.001 | 5.373 | 0.023 | 0.052 |
Stress exposure × subjective stress2 | 0.000 | 1 | 0.000 | 1.863 | 0.175 | 0.019 |
Error | 0.012 | 98 | 0.000 | |||
Total | 0.014 | 106 | 0.000 |
There was a significant difference in Stroop interference changes between the controllable and uncontrollable stress groups,
There was a significant interaction between stress controllability and the quadratic effects of subjective stress in predicting change in Stroop interference,
We conducted analyses to confirm that baseline differences in Stroop performance did not drive the effects of group noted above. A regression predicting baseline interference scores by group contrast codes confirmed that there were no significant differences in Stroop performance between subjects randomly assigned to each of the three stress conditions,
We conducted analyses to investigate whether experimental groups differed in Stroop accuracy, either at baseline or over the course of testing. There were no differences in baseline incongruent or neutral trial accuracy between groups (
We conducted a full regression in which changes in incongruent trial accuracy were predicted by group contrast codes, the linear and quadratic effects of subjective stress, and interactions between these variables. This analysis revealed a marginal difference in accuracy change between the CSt and USt groups in which having behavioral control predicted a greater improvement in incongruent trial accuracy,
All groups showed similar positive affect (
The results of Experiment 1 suggest that controllability of stress, as well as individual differences in subjective response to stress, together influence the impact of stress exposure on executive functioning in the color-word Stroop. Specifically, these results show that characteristics of stress exposure such as controllability and subjective response can cause stress to have either beneficial or harmful effects on cognitive abilities. Exposure to controllable stress improved executive functioning only when that stress was experienced as moderate. In contrast, stress response had no relationship with executive functioning when stress exposure was uncontrollable. Furthermore, when equating participants on levels of subjective stress, those who learned to control stressors showed improved Stroop performance compared to those exposed to uncontrollable stress.
Although these results suggest the importance of controllability in moderating the effects of stress on EF, it is not clear from this study which aspects of controllability are essential to this relationship. The question of specifying which aspects of controllability actively drive effects has been controversial. Some studies have suggested that differing rates of failure account completely for learned helplessness effects (Matute,
To test the hypothesis that non-contingency between behavioral actions and stressors is critical to the effects we observed in Experiment 1, we equated our controllable and uncontrollable stress groups on performance feedback, so that participants in both groups would receive the same total amount of success and failure feedback over the course of testing. However, it was once again impossible for participants in the uncontrollable condition to learn how to control stressors or accurately anticipate the type of feedback they received for each trial.
Participants were 90 undergraduate volunteers ages 18–24 from introductory psychology courses at the University of Colorado Boulder (Table
Condition | Sample |
Self-report |
Cognitive tasks |
||||
---|---|---|---|---|---|---|---|
Subjective stress | Subjective control |
BDI score |
Pre-stress Stroop interference |
Post-stress Stroop interference |
Change in interference |
||
CSt | 30 (18) | 17.13 (4.32) | 5.57 (1.33) | 9.20 (6.78) | 0.0159 (0.0091) | 0.0105 (0.0090) | −0.0054 (0.0101) |
USt | 28 (14) | 15.26 (5.38) | 2.61 (2.64) | 9.46 (5.79) | 0.0118 (0.0127) | 0.0073 (0.0101) | −0.0045 (0.0155) |
NSt | 32 (16) | 12.99 (4.03) | n/a | 11.16 (5.89) | 0.0165 (0.0137) | 0.0100 (0.0104) | −0.0065 (0.0151) |
Total | 90 (48) | 17.16 (5.00) | 4.14 (2.54) | 9.97 (6.17) | 0.0149 (0.0120) | 0.0094 (0.0098) | −0.0055 (0.0135) |
Study procedures were the same as in Experiment 1.
Individual testing and materials were the same as in Experiment 1, except as noted.
The stress manipulation was modified for Experiment 2 to hold the rates of success and failure feedback constant across CSt and USt groups. Every research participant responded to identical choice-RT trials, and a moving-window for response speed ensured that everyone was able to beat the time limits on 70% of trials. Again, the NSt group never received performance feedback (green fixation box after every response). The CSt participants received accurate, response-contingent performance feedback (success feedback for 70% of trials), and received short noises on successful trials (70%) and long noises on failed trials (30%). The USt participants received an identical rate of success feedback (70%) that was, however, not contingent on response speed, and were exposed to short (70%) and long (30%) noises that were unrelated to their response speed or to performance feedback. Noise exposures were once again equated between the CSt and USt groups, so participants in these groups received the same total number of short and long noises.
Participants in the CSt and USt groups completed a practice block (20 trials) without noise exposure or feedback, a feedback block (60 trials) that included performance feedback as described above but no noise exposure, and a stress block (60 trials) that included performance feedback and noise exposure as described above. These trial blocks were shorter in Experiment 2 to minimize the amount of noise exposure per participant, and equate the amount of long noises (reported in pilot testing as considerably more stressful) experienced by each participant across Experiments 1 and 2. Participants in the NSt group completed the same task but did not receive feedback or noise stress during any block
All assessments of executive functioning, mood, affect, and subjective stress response, were conducted in Experiment 2 with the same measures as implemented in Experiment 1. Again, we also conducted regressions including BDI-II score and participant sex as covariates. Unless otherwise indicated, the significance of the results was not altered by the addition of these covariates and we report simple analyses only.
Data processing and analyses were the same as for Experiment 1.
Confirming that the controllability manipulation was effective, the CSt group (
Next we investigated the effects of stress exposure and controllability on subjective stress responses. Again, including sex as a covariate revealed a significant difference in subjective stress responses between men and women, across groups; women reported higher stress (
To examine the interactive effects of stress controllability and subjective stress on executive functioning, we conducted regression analysis in which change in Stroop interference was predicted by group contrast-coded predictors, subjective stress (both linear and quadratic effects), and the interactions of these predictors (Table
Source | SS | df | MS | |||
---|---|---|---|---|---|---|
Model | 0.002a | 8 | 0.000 | 1.092 | 0.378 | 0.102 |
(Constant) | 0.003 | 1 | 0.003 | 16.933 | 0.000 | 0.180 |
Controllability | 0.000 | 1 | 0.000 | 0.229 | 0.633 | 0.003 |
Stress exposure | 0.000 | 1 | 0.000 | 0.160 | 0.691 | 0.002 |
Subjective stress | 0.000 | 1 | 0.000 | 0.052 | 0.820 | 0.001 |
Subjective stress2 | 0.000 | 1 | 0.000 | 0.359 | 0.551 | 0.005 |
Controllability × subjective stress | 0.001 | 1 | 0.001 | 4.991 | 0.028 | 0.061 |
Stress exposure × subjective stress | 0.000 | 1 | 0.000 | 0.371 | 0.544 | 0.005 |
Controllability × subjective stress2 | 0.000 | 1 | 0.000 | 0.035 | 0.852 | 0.000 |
Stress exposure × subjective stress2 | 0.000 | 1 | 0.000 | 0.011 | 0.918 | 0.000 |
Error | 0.014 | 77 | 0.000 | |||
Total | 0.016 | 85 | 0.000 |
There was a significant interaction between stress controllability and the linear effect of subjective stress,
In the full regression described above, there were no quadratic effects of subjective stress detected when controlling for group and group interactions. This result could indicate that different groups clustered on different parts of the quadratic curve, so that equating participants on group status simply washed out the quadratic effect. In consideration of this possibility, and to examine the effects of stress response on executive functioning across groups, we conducted a regression predicting change in Stroop interference by the linear and quadratic effects of subjective stress. Examined this way, there was a significant quadratic effect such that moderate levels of stress predicted reduced Stroop interference while low or high levels of subjective stress predicted increased Stroop interference,
To determine whether there were group differences in Stroop performance at baseline that could contribute to these effects, we regressed baseline interference scores on group contrast codes. This analysis confirmed that participants randomly assigned to each of the three stress conditions showed comparable Stroop interference at baseline,
We conducted analyses to investigate whether experimental groups differed in Stroop accuracy. There were no differences in baseline incongruent or neutral trial accuracy between groups (
We conducted a full regression in which changes in incongruent trial accuracy were predicted by group contrast codes, the linear and quadratic effects of subjective stress, and interactions between these variables. This analysis revealed a significant difference in accuracy change between the CSt and USt groups in which having behavioral control predicted a greater improvement in incongruent trial accuracy,
All groups showed comparable, and low (
These results support the view that non-contingency is an active ingredient in the effects of uncontrollability on the relationship between subjective stress and executive functioning. Once again, stress response only predicted Stroop interference in the group exposed to controllable (contingent) stressors.
Stress is ubiquitous, and previous research suggests it can have both negative (Oei et al.,
These results are consistent with previous research suggesting the importance of controllability (Dickerson and Kemeny,
In addition, these results demonstrate for the first time that controllability and subjective stress influence the effect of stress on a measure of general EF (i.e., common EF; Friedman et al.,
Comparing Experiments 1 and 2 leads to some tentative conclusions regarding the critical aspects of controllability that affect behavioral functioning. Specifically, these results suggest that non-contingency between behavioral responses and stressors is sufficient to alter the relationship between subjective stress and Stroop performance, as demonstrated by Experiment 2. These results are consistent with the theory that exposure to non-contingency causes disruption to basic learning systems (Oakes,
The results of these experiments raise several questions. First, the current study is limited by the absence of physiological measures of stress reactivity, which would enable us to compare subjective and objective individual differences in stress responses. Previous research has shown that subjective ratings are related to physiological reactions, but are not perfectly correlated (Elzinga and Roelofs,
Second, it remains an open question why subjective response to stress was related to Stroop performance in the group exposed to controllable stress, but not in the group exposed to uncontrollable stress. One possibility is that uncontrollable stress leads to different neural responses than controllable stress, and thus does not affect EF performance in the same way. In rodents, the inability to learn to escape a stressor is related to decreased activity in neural systems responsible for down-regulating activity in stress-response regions; thus stress responses are permitted to occur unchecked, ultimately leading to a sensitized arousal system that reacts more readily to mild provocation (Maier and Watkins,
Finally, in these experiments we detected no effects of mood or affect. Because this research was conducted with a non-clinical sample, and the majority of participants (71%) reported scores below the cut-point for mild dysphoria (BDI > 12; Kendall et al.,
The results of this research are relevant for anyone who wants to capitalize on the potential of stress to enhance goal-directed behavior, while minimizing the negative effects of stress. In particular, this research is relevant as we set physical or academic goals for ourselves that are tuned to our individual appraisals of difficulty and controllability. Future studies investigating controllability and reactivity in settings such as education or clinical treatment may provide insight on how stress exposure can be a powerful source of benefit for students, clients, and others hoping to reap the helpful effects of stress.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
1Original recruitment included a sample size of 127 participants; however, 3 participants in the CSt condition and 1 participant in the USt condition failed to complete the experiment due to computer error, and 14 participants in the NSt condition failed to complete self-report measures due to experimenter error. For these reasons, analyses were performed on a sample size of
2We expected that response speed on choice-RT trials would vary between groups, given that the no-stress group did not receive performance feedback and therefore may have been less motivated to respond quickly on choice-RT trials. Analyses revealed an effect of stress exposure, in which the NSt group had slower response times in both testing blocks than the CSt or USt group (
3Recruitment included an additional two participants in the USt group, however, these participants failed to complete the experiment due to (1) computer error, and (2) one participant reported color-blindness that caused him to be unable to perform the Stroop task.
4As in Experiment 1, the NSt group had slower response times in both testing blocks than the CSt or USt group (