The Ego Could Be Depleted, Providing Initial Exertion Is Depleting
A Preregistered Experiment of the Ego Depletion Effect
Abstract
Abstract. The ego depletion effect has been examined by over 300 independent studies during the past two decades. Despite its pervasive influence, recently this effect has been severely challenged and asserted to be a fake. Based on an up-to-date meta-analysis that examined the effectiveness of each frequently used depleting task, we preregistered the current experiment with the aim to examine whether there would be an ego depletion effect when the Stroop task is used as the depleting task. The results demonstrated a significant ego depletion effect. The current research highlights the importance of the depleting task’s effectiveness. That is to say, the “ego” could be “depleted,” but only when initial exertion is “depleting.”
The ego depletion effect refers to the phenomenon that initial exertion of self-control impairs subsequent self-regulatory performance, which has been examined by over 300 independent studies during the past two decades since it was first reported (Baumeister, Bratslavsky, Muraven, & Tice, 1998; Muraven, Tice, & Baumeister, 1998). Despite its pervasive influence, recently this effect has been severely challenged and asserted to be a fake. A project including 23 laboratories (N = 2,141) in both English-speaking countries and non-English-speaking countries failed to replicate the ego depletion effect (Hagger et al., 2016). Although this replication provides seemingly robust evidence casting doubt on the existence of ego depletion, cautious attention has to be paid to the effectiveness of the depleting task (i.e., a modified e-crossing task) used in the replicating project. As revealed by a complementary analysis of the replicating data, participants generally did not consider the e-crossing task as “depleting.” However, for those who considered it as effortful, there was an ego depletion effect (Dang, 2016).
An up-to-date meta-analysis of ego depletion examined the effectiveness of each frequently used depleting task and found that the Stroop task should be one of the most effective depleting tasks (Hedge’s g = 0.44; Dang, in press). Therefore, we preregistered the current experiment with the aim to examine whether there would be an ego depletion effect when the Stroop task is used as the depleting task. The sample size, procedure, and the analytical plan have been specified in advance in the preregistration (https://osf.io/ydc7z/).
We used G*Power to determine the needed sample size, which showed that a sample with 160 participants (80 in each of the two conditions) would be able to detect a comparable effect size with a power of .80 (two tails). Meanwhile, previous research revealed three possible moderating individual difference variables: trait self-control (Imhoff, Schmidt, & Gerstenberg, 2014), action orientation (Dang, Xiao, Shi, & Mao, 2015; Gröpel, Baumeister, & Beckmann, 2014), and lay theories about willpower (Job, Dweck, & Walton, 2010). Therefore, they were included in the current experiment to examine whether the depletion manipulation would interact with individual difference variables as in previous studies.
Method
Participants and Procedure
In all, 176 students from a Chinese university (83 males and 93 females; mean age = 23.24 years, SD = 2.58) were recruited in return for 25 RMB (approximately $4.70). In the experiment, participants first completed a short questionnaire measuring those three individual difference variables. Next, they received the depletion manipulation (i.e., the Stroop task). After the Stroop task, they answered four manipulation check questions regarding effort, difficulty, fatigue, and frustration on a 7-point scale (Hagger et al., 2016). Finally, participants finished an antisaccade task that requires high level of attentional control (Unsworth, Spillers, Brewer, & McMillan, 2011) and has been used in ego depletion studies (e.g., Dang, Xiao, Liu, Jiang, & Mao, 2016). The e-prime script of the experiment is available online (https://osf.io/3k7sh/).
Individual Difference Measures
Action orientation was measured by the Demand-Related Action Orientation subscale (AOD) of the Action Control Scale (Jostmann & Koole, 2007). The AOD scale consists of 12 items. Each item describes a demanding situation and an action-oriented versus a state-oriented coping way. Participants were asked to indicate the way that best describes their own reaction to that situation. Action-oriented responses were coded as 1 whereas state-oriented responses as zero. Scores summed for the entire scale could range from 0 to 12. The internal consistency of this scale in the current study is 0.72.
The six items developed by Job et al. (2010, Study 1) were used to measure the belief about willpower. Participants responded on a 6-point rating scale (1 = strongly disagree, 6 = strongly agree). Items were scored so that higher values indicate greater agreement with the unlimited-resource theory. The internal consistency of this scale in the current study is 0.83.
Trait self-control was measured by the 13-item Brief Self-Control Scale (Tangney, Baumeister, & Boone, 2004). Participants indicated the extent to which they agree with each statement on a scale from 1 (= strongly disagree) to 5 (= strongly agree). Higher score represents better self-control. The internal consistency of this scale in the current study is 0.81. These three measures were translated into Chinese by the first author who discussed with other authors to form the final versions. The descriptive statistics are depicted in Table 1.
Depletion Manipulation
After the individual difference measure, participants were randomly assigned to the depletion condition and the control condition. In the depletion condition, they finished a Stroop task in which most trials were incongruent (256 trials, 75% incongruent, four different colors). In the control depletion, all trials were congruent. Participants were required to read the color of the word aloud and then press the spacebar to proceed toward the next trial.
Manipulation Check Measures
After the Stroop task, participants answered four manipulation check questions regarding effort (“How much effort did you put into the color-naming task”), difficulty (“How difficult did you find the color-naming task”), fatigue (“How tired do you feel after doing the color-naming task”), and frustration (“Did you feel frustrated while you were doing the color-naming task”) on a 7-point scale (Hagger et al., 2016).
The Dependent Measure
Following the manipulation check measures, participants were required to finish an antisaccade task (Dang et al., 2016; Unsworth et al., 2011). The main task was to identify three target letters (B, P, and R) by pressing a corresponding key (the keys 1, 2, and 3, respectively) as quickly and accurately as possible (Unsworth et al., 2011). At the beginning of each trial, a fixation cross appeared for 200 ms on the screen with a black background. A flashing white “=” was then flashed either to the left or to the right of the fixation cross for 100 ms, followed by a 50 ms blank screen and a second appearance of the sign “=” for 100 ms at the same location as the first one. This procedure made it appear as though the sign “=” flashed onscreen, which would easily grasp participants’ attention. Following another 50 ms blank screen, the target stimulus (a letter B, P, or R) appeared in the opposite location of the flashing sign for 100 ms, followed by a letter “H” for 50 ms masking and a number “8” which remained onscreen at the same location as the target stimulus until a response was given. This task requires high level of self-control. First, participants have to actively maintain the goal of shifting attention. Any lapse in attention would lead to a reflexive prosaccade to the flicking cue and thus an error. Second, even if the task goal could be maintained, there is still a need to overcome the prepotent response of looking toward the flicking cue in order to initiate the antisaccade according to the goal. Participants received 30 practice trials (12 practice trials for learning the response mapping and 18 practice trials for doing the formal test) and 120 real trials. The primary dependent variable was the accuracy of the antisaccade task. The response time (RT) was also examined after trimming (i.e., longer than 200 ms and shorter than 2,000 ms; Unsworth et al., 2011).
Results
As shown in Table 2, the differences in four manipulation check items were all significant, ts > 3.00, ps < .01. The accuracy of the antisaccade task also showed significant result. Participants in the depletion condition (M = 0.60, SD = 0.18) performed worse than did those in the control condition (M = 0.68, SD = 0.15), t(174) = −2.92, p = .004, Hedge’s g = 0.48. 95% CI = [0.18, 0.78]. This effect kept significant after controlling for age and gender, F(1, 172) = 7.52, p = .007, η2p = .04. No significant between-group difference was found on the RT, t(174) = −0.66, p = .508, Hedge’s g = −0.10, 95% CI = [−0.39, 0.20]. When the RT was included as a covariate, the effect on the accuracy was still significant, F(1, 173) = 12.45, p = .001, η2p = .07, which rules out the possibility that the accuracy difference was influenced by speed-accuracy trade-off. We also computed a composite index of the four manipulation check items. Across conditions, this index was not only correlated with antisaccade accuracy, r = −.24, p = .001, but also marginally significantly correlated with antisaccade RT, r = .14, p = .067, therefore suggesting an association between phenomenology and performance. The data are available online (https://osf.io/3k7sh/).
Multiple regression analysis was employed to test whether individual difference variables would interact with the depletion manipulation. In the first step we entered experimental condition and one individual difference variable (centered). Their interaction term was entered in the second step. As shown in Table 3, all three interactions were not significant on both the accuracy and the RT. These results remained the same after controlling for age and gender.
Discussion
In summary, the current preregistered experiment demonstrated a significant ego depletion effect when the Stroop task was employed as the depleting task. The effect size is comparable to that found in Dang’s (in press) meta-analysis. This highlights the importance of the depleting task’s effectiveness. That is to say, the “ego” could be “depleted,” but only when initial exertion is “depleting.” Note that the current experiment was fully computerized, therefore it could be easily implemented in multi-lab replications. Meanwhile, more preregistered studies are needed for verifying the effectiveness of other depleting tasks, especially those yielding homogeneous effects in the meta-analysis such as the attention essay task and the emotion video task (Dang, in press).
This work was supported by National Basic Research Program of China (973 Program 2015CB351800).
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