> The overall “effect size,” a measure of the strength of a finding, dropped by about half across all of the studies. In general, if you conduct an experiment

> The overall “effect size,” a measure of the strength of a finding, dropped by about half across all of the studies. In general, if you conduct an experiment, then conditional on finding significance the estimate of the effect size is going to be an overestimate of the true effect size. This is because the data that was extreme enough to produce a low p-value is also likely to be more extreme than the true population. Obviously this effect is less important when the true effect size is large enough - in high-powered studies. So this might not actually be so important: it may also mean that the effect size estimated in the original paper was simply miscalculated and estimated to be too high.