It’s not all bad news
Here’s a cool pre-print examining the quality of evidence in studies of the genetics of short-term memory in fruit flies (Tumkaya, Ott, & Claridge-Chang, 2018). The paper conducts a meta-analysis of different genes that have been linked to altered olfactory memory. There’s lots of good news. Most genes were identified via studies with internal direct replications and large sample-sizes. No hint of publication bias was detected. Effect sizes across replications were largely stable–no decline effects were observed. Yeah!
The only glimmer of bad news is that most of the genes have not been independently replicated, suggesting either that no one is interested in them or that external replications have been conducted but not published (in fact, not a single disputing paper was identified).
It seems clear that when researchers use adequate sample sizes, the resulting evidence base comes out much more reliable and interpretable. Hooray for fly labs.