Back in 2010, Jonah Lehrer wrote a big New Yorker feature called “The Truth Wears Off“. In it, he called attention to anecdotal observations that many of the effects and phenomena scientists study seem to shrink over time. Lehrer’s article popularized the term “decline effect” to summarize this pattern. Recently, some striking examples of the decline effect have been reported in ecology, such as in the declining effect of ocean acidification on fish behavior. Further back, Jennions & Møller (2002) found that decline effects were ubiquitous in the (relatively few) ecological and evolutionary meta-analyses that had been published at the time.
Outstanding undergraduate Laura Costello and I decided to revisit the prevalence of decline effects in ecological research, using my quite comprehensive compilation of all the data from 466 ecological meta-analyses. We’re very excited that the paper is now online at Ecology. You should click through and read it (of course, I would say that!). But the tl;dr read version is that the only common decline effect in ecology is in the decline effect itself. The truth no longer “wears off” in ecology, if it ever did. Decline effects might’ve been ubiquitous in ecological meta-analyses back in the 1990s, but they aren’t any more. Only ~3-5% of ecological meta-analyses exhibit a true decline in mean effect size over time (as distinct from regression to the mean, which happens even if effect sizes are published in random order over time). Read the paper if you’re curious about our speculations as to why decline effects are now rare in ecology.
This is the third paper of mine that grew out of a blog post, which is my tissue-thin justification for sharing news of the paper in a blog post. 🙂