Yesterday, ResearchGate suggested that I read a new article reporting that ego depletion can cause aggressive behavior. This was a surprise to me because word has it that ego depletion does not exist, so surely it cannot be a cause of aggressive behavior.
The paper in question looks about like you'd expect: an unusual measure of aggression, a complicated 3 (within) × 2 (between) × 2 (between) design, a covariate tossed into the mix just for kicks, a heap of measures collected and mentioned in a footnote but not otherwise analyzed. It didn't exactly change my mind about ego depletion, much less its role in aggressive behavior.
But it'd be hypocritical of me to criticize this ill-timed paper without mentioning the time I reported an ego-depletion effect through effect-seeking, exploratory analysis. I've also been meaning to change my blogging regimen up a bit. It's time I switched from withering criticism to withering self-criticism.
The paper is Engelhardt, Hilgard, and Bartholow (2015)
, "Acute exposure to difficult (but not violent) video games dysregulates cognitive control." In this study, we collected a hearty sample (N = 238) and had them play one of four modified versions of a first-person shooter game, a 2 (Violence: low, high) × 2 (Difficulty: low, high) between-subjects design.
To manipulate violence, I modified the game's graphics. The violent version
had demons and gore and arms bouncing across the floor, whereas the less violent version
had silly-looking aliens being warped home. We also manipulated difficulty: Some participants played a normal version of the game in which monsters fought back, while other participants played a dumb-as-rocks version
where the monsters walked slowly towards them and waited patiently to be shot.
After the game, participants performed a Spatial Stroop task. We measured the magnitude of the compatibility effect, figuring that larger compatibility effects would imply poorer control. We also threw in some no-go trials, on which participants were supposed to withhold a response.
Our hypothesis was that playing a difficult game would lead to ego depletion, causing poorer performance on the Spatial Stroop. This might have been an interesting refinement on the claim that violent video games teach their players poorer self-control
We looked at Stroop compatibility and found nothing. We looked at the no-go trials and found nothing. Effects of neither violence nor of difficulty. So what did we do?
We needed some kind of effect to publish, so we reported an exploratory analysis, finding a moderated-mediation model that sounded plausible enough.
We figured that maybe the difficult game was still too easy. Maybe participants who were more experienced with video games would find the game to be easy and so would not have experienced ego depletion. So we split the data again according to how much video game experience our participants had, figuring that maybe the effect would be there in the subgroup of inexperienced participants playing a difficult game.
The conditional indirect effect of game difficulty on Stroop compatibility as moderated by previous game difficulty wasn't even, strictly speaking, statistically significant: p = .0502. And as you can see from our Figure 1, the moderator is very lopsided: only 25 people out of the sample of 238 met the post-hoc definition of "experienced player."
And the no-go trials on the Stroop? Those were dropped from analysis: our footnote 1 says our manipulations failed to influence behavior on those trials, so we didn't bother talking about them in the text.
So to sum it all up, we ran a study, and the study told us nothing was going on. We shook the data a bit more until something slightly more newsworthy fell out of it. We dropped one outcome and presented a fancy PROCESS model of the other. (I remember at some point in the peer review process being scolded for finding nothing more interesting than ego depletion, which was accepted fact and old news!)
To our credit, we explicitly reported the exploratory analyses as being exploratory, and we reported p = .0502 instead of rounding it down to "statistically significant, p = .05." But at the same time, it's embarrassing that we structured the whole paper to be about the exploratory analysis, rather than the null results.
In the end, I'm grateful that the RRR has set the record straight on ego depletion. It means our paper probably won't get cited much except as a methodological or rhetorical example, but it also means that our paper isn't going to clutter up the literature and confuse things in the future.
In the meantime, it's showed me how easily one can pursue a reasonable post-hoc hypothesis and still land far from the truth. And I still don't trust PROCESS.