Another blow for ego-depletion theory

Ego depletion is the notion that willpower is a fuel that gets burned away by effort, and once it burns low we lose our focus and bow to our immediate desires. However, this once dominant theory has recently come into question, thanks in part to a large-scale replication that failed to find an ego-depletion effect and a meta-analysis that argued that the size of the effect is minimal. Complicating the picture, other recent findings have provided a strong demonstration of the effect. But now researchers from Johannes Gutenberg University in Mainz have released a pre-print at PsyArxiv in which they suggest the debates over the size of the ego-depletion effect are missing the point because when you look over the long-term, ego depletion becomes meaningless.

The team, led by Mario Wenzel, built experiments around the classic ego-depletion design: some participants performed an initial mentally demanding task designed to make them ego-depleted whereas others acted as controls and performed a low-effort version. Next, all participants performed a second mentally demanding task. Poorer performance on this second task by the ego-depleted group, as compared with the controls, was taken as evidence of ego depletion. However, unlike in most previous research, Wenzel and his colleagues had their participants repeat these pairs of tasks several times, to see if any effects of ego depletion would accumulate.

For the first experiment, the researchers asked their participants to start by completing a difficult or easy version of the Multi-Source Interference Task (MSIT). This involved quickly responding to simple stimuli on a computer screen by pressing the button corresponding to the odd one out. The 18 student participants in the control group started with a dead easy version that involved displays like "xx1" with an obvious odd-one-out, whereas the 46 students in the ego-depletion condition completed a harder version that involved responding to whichever digit was the odd-one-out based purely on its colour, while ignoring the uniqueness or not of its numerical value (such as the red "4" in arrays like "442").

Next, all the participants completed the same second task, which was another colour version of the MSIT – only this time colours had to be ignored entirely, just focusing on the odd number out.

Once participants had done the initial and second tasks, they started again, completing another pair of MSIT tasks – and then repeated this in a third "block" of tasks, then again in a fourth. If willpower was being used up by these tasks, you would expect performance to deteriorate even more in the later blocks.

But, if anything, the results were the other way around. Wenzel's team found that the ego-depletion effect was largest in the first block and then diminished (across the four blocks, in statistical terms the effect sizes were very small, from .065 to .001, and mostly non-significant).

For a second experiment with 93 students, the researchers pushed the time horizon further, to see if the fuel needle would finally hit empty. This time there were 12 "blocks" involving various pairs of tasks, with the second task always the classic Stroop test (in which participants must identify the font colour of colour-denoting words, such as "red" written in blue ink). For instance, participants might do one of the MSITs paired with the the Stroop, then a version of the Go-No-Go task paired with the Stroop, then a copying task paired with the Stroop, and so on. When participants were being hit with the harder versions of the initial tasks, how did their Stroop performance fare?

Participants agreed (as they did in the first experiment) that the hard versions of the preliminary tasks required more self-control. But again, over the course of the blocks, any evidence of ego depletion, in terms of greater declining performance among the participants completing the harder initial tasks, turned out to be small and statistically non-significant – this despite the fact that mild ego depletion often did show up during the very first block. In other words, the ego-depletion effect did the opposite of what we might expect – if anything, participants' willpower replenished over time (a finding that's similar to the recently documented example of reverse ego depletion in India).

The researchers conceded that part of the explanation may be an effect of practice (even in the second experiment that used a mix of tasks to counteract this possibility). Maybe tackling a mix of effortful tasks that occasionally repeat is something you ease into after a bit. But this doesn't really let ego depletion off the hook: if it only adds up to anything in the narrow window between starting a task and getting to grips with it, it can't be all that important – and would seem to have little bearing on the domains that it has been associated with, such as keeping up the willpower to get in shape, pass your finals, or stay off the cigarettes. In this pre-print paper, which has been submitted for publication in a peer-reviewed journal, the researchers recommend that we focus a little more attention on the mechanisms that matter for life-sized timespans, and less on laboratory-induced blips in performance.

Further reading

—Practice conquers it all: Even if the ego depletion effect is genuine, it may not be relevant

About the author

Alex Fradera (@alexfradera) is Staff Writer at BPS Research Digest