Effort Matters: A Commentary on “Is Trying Harder Enough?”

“There is zero causal effect of effort on scores,” concluded a recent study, Is Trying Harder Enough? Causal Analysis of the Effort-IQ Relationship Suggests Not (Bates, 2025). The study included two experiments. Each paid a treatment group a two-pound reward if they increased their performance on a subsequent IQ test after an initial test. The estimated effects of effort were not significantly different from zero in either experiment.I argue that this conclusion commits the statistical non-significance fallacy—just because an effect size is not significantly different from zero does not mean that the effect really is zero. Confidence intervals reported in the study are too large for strong inferences to be made. This is in part because the sample size (1,737) and financial incentives offered are too small. I estimate the study would need a sample size around four times larger, at 6,500 participants, to have 80% power to reject the null, if the true effect of effort were moderate in size. Nevertheless, I find that by incorporating sensible control variables (such as IQ from the initial test) or by pooling data with a prior study (Bates & Gignac, 2022), a significant effect of effort can be found. Confidence intervals in my re-analysis are very large, making the magnitude of the effect of effort uncertain.