Can interventions meaningfully increase intelligence? If so, how? The Database of Raising Intelligence is a continuously updated compendium of randomized controlled trials that were designed to increase intelligence. In this article, the authors examine nearly every available intervention involving children from birth to kindergarten, using meta-analytic procedures when more than 3 studies tested similar methods and reviewing interventions when too few were available for meta-analysis. This yielded 4 meta-analyses on the effects of dietary supplementation to pregnant mothers and neonates, early educational interventions, interactive reading, and sending a child to preschool. All 4 meta-analyses yielded significant results: Supplementing infants with long-chain polyunsaturated fatty acids, enrolling children in early educational interventions, reading to children in an interactive manner, and sending children to preschool all raise the intelligence of young children.

In five preregistered studies, we assess people’s tendency to believe “kids these days” are deficient relative to those of previous generations. Across three traits, American adults (N = 3458; M_age = 33 to 51 years) believe today’s youth are in decline; however, these perceptions are associated with people’s standing on those traits. Authoritarian people especially think youth are less respectful of their elders, intelligent people especially think youth are less intelligent, and well-read people especially think youth enjoy reading less. These beliefs are not predicted by irrelevant traits. Two mechanisms contribute to humanity’s perennial tendency to denigrate kids: a person-specific tendency to notice the limitations of others where one excels and a memory bias projecting one’s current qualities onto the youth of the past. When observing current children, we compare our biased memory to the present and a decline appears. This may explain why the kids these days effect has been happening for millennia.

Failures to replicate evidence of new discoveries have forced scientists to ask whether this unreliability is due to suboptimal implementation of methods or whether presumptively optimal methods are not, in fact, optimal. This paper reports an investigation by four coordinated laboratories of the prospective replicability of 16 novel experimental findings using rigour-enhancing practices: confirmatory tests, large sample sizes, preregistration and methodological transparency. In contrast to past systematic replication efforts that reported replication rates averaging 50%, replication attempts here produced the expected effects with significance testing (P < 0.05) in 86% of attempts, slightly exceeding the maximum expected replicability based on observed effect sizes and sample sizes. When one lab attempted to replicate an effect discovered by another lab, the effect size in the replications was 97% that in the original study. This high replication rate justifies confidence in rigour-enhancing methods to increase the replicability of new discoveries.