Effort Interventions Versus Motivation Interventions
Changing the friction of an action works better than changing how much somebody wants to do it. Yu Luo and colleagues organise behavioural interventions along six cognitive processes, perception, memory, attention, effort, intrinsic motivation and extrinsic motivation, and the headline across one hundred and eighty-four field experiments with real behavioural measures, covering around two point two million people between 2008 and 2021, is that interventions changing effort are more effective than interventions changing intrinsic motivation. The same analysis found nudge and sludge effects of similar size.
What it is
The corpus is deliberately narrow in one respect that matters: these are field experiments with real behavioural measures rather than stated intentions, which is what makes the ordering worth something. The uncomfortable corollary of the nudge-and-sludge symmetry is that friction is a lever working in both directions, so whoever holds it can also use it against you. The practical reading for anyone trying to pay attention to something is that a measure shortening the path to the work you intend to do, or lengthening the path to the thing that pulls you away, is doing the kind of thing this result supports, while a measure trying to make you want the work more is doing the kind of thing it does not.
In effect
The convergence matters more than either result on its own. Two meta-analyses built on different taxonomies and different corpora arrive at the same ordering, with structure and effort at the top and intention-reinforcement at the bottom. A third analysis, correcting the nudge literature for publication bias, refutes the information and assistance categories and leaves structure undecided. Three passes over this evidence point at friction and away from motivation, and that convergence is sturdier than any one of the three figures. It is also the version of the structural case with the best evidence behind it, and it belongs to neither side of the usual individual-against-structural argument.
What it does not say
It does not come with a clean bill of health. The authors' own caution is that the results need to be interpreted with care because of a potential publication bias, which is why the status here is mixed rather than robust, and why this page is written beside the decision-structure page rather than instead of it. The six-process framework is also a classification of interventions rather than a measurement of mechanisms, so an intervention labelled as changing effort is labelled by what it does to the path rather than by anything observed inside the person. And none of it requires any particular model of willpower to be true.
Sources
- Luo, Y., Li, A., Soman, D., & Zhao, J. (2023). "A meta-analytic cognitive framework of nudge and sludge." Royal Society Open Science, 10(11), 230053. doi:10.1098/rsos.230053. Open access, abstract read in full; Luo first author, University of British Columbia. 184 field experiments with real behavioural measures, 2,245,373 participants, 2008 to 2021.
- Mertens, S., Herberz, M., Hahnel, U. J. J., & Brosch, T. (2022). "The effectiveness of nudging: A meta-analysis of choice architecture interventions across behavioral domains." PNAS, 119(1), e2107346118. doi:10.1073/pnas.2107346118. Abstract read in full; Mertens first author. The sibling ordering.
- Maier, M., Bartoš, F., Stanley, T. D., Shanks, D. R., Harris, A. J. L., & Wagenmakers, E.-J. (2022). "No evidence for nudging after adjusting for publication bias." PNAS, 119(31), e2200300119. doi:10.1073/pnas.2200300119. Full text read; a Letter, not a research article. The bias correction that leaves structure undecided.