The impact of environmental interventions among mouse siblings on the heritability and malleability of general cognitive ability

Abstract

General cognitive ability can be highly heritable in some species, but at the same time, is very malleable. This apparent paradox could potentially be explained by gene-environment interactions and correlations that remain hidden due to experimental limitations on human research and blind spots in animal research. Here, we shed light on this issue by combining the design of a sibling study with an environmental intervention administered to laboratory mice. The analysis included 58 litters of four full-sibling genetically heterogeneous CD-1 male mice, for a total of 232 mice. We separated the mice into two subsets of siblings: a control group (maintained in standard laboratory conditions) and an environmental-enrichment group (which had access to continuous physical exercise and daily exposure to novel environments). We found that general cognitive ability in mice has substantial heritability (24% for all mice) and is also malleable. The mice that experienced the enriched environment had a mean intelligence score that was 0.44 standard deviations higher than their siblings in the control group (equivalent to gains of 6.6 IQ points in humans). We also found that the estimate of heritability changed between groups (55% in the control group compared with non-significant 15% in the enrichment group), analogous to findings in humans across socio-economic status. Unexpectedly, no evidence of gene-environment interaction was detected, and so the change in heritability might be best explained by higher environmental variance in the enrichment group. Our findings, as well as the 'sibling intervention procedure' for mice, may be valuable to future research on the heritability, mechanisms and evolution of cognition.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Measuring and understanding individual differences in cognition

“…Moreover, several experimental studies have shown that artificial selection for cognitive traits or brain size can drive directional changes across generations [56 -59]. However, understanding the heritability of cognitive performance (and its evolutionary consequences; see below) is far from straightforward, as discussed by two papers in this special issue [8,9]. As heritability is assessed by partitioning variance between environmental and genetic components, heritability estimates are highly dependent on the local environment.…”

“…As heritability is assessed by partitioning variance between environmental and genetic components, heritability estimates are highly dependent on the local environment. For example, Sauce et al [8] show strong heritability of cognitive performance in mice raised in standard laboratory conditions, while in groups of mice exposed to environmental enrichment, the increased environmental variance component leads to heritability estimates of effectively zero. Heritability estimates may also be highly specific to particular cognitive traits.…”

Avian ecological epigenetics: pitfalls and promises

“…We have to understand the causes and consequences of intra-individual variation in cognitive performance to understand how natural selection shapes cognition (Boogert et al 2018). A recent study found that cognitive ability is heritable in mice, but also highly malleable according to environmental effects (Sauce et al 2018). Intra-individual variation in cognitive performance is thus possibly the result of constant interaction between genes and experience that may be mediated by epigenetic mechanisms (Sweatt 2019).…”

Stress hormones, social associations and song learning in zebra finches

“…Alternatively, brothers might not necessarily copy each other's songs directly, but show similar song learning tendencies (e.g. they may, genetically and/or through early-life effects, be predisposed to attend to the same cues in their (social) environment, as seen in mouse sibs [ 64 ]), resulting in more similar songs indirectly. It is impossible to distinguish between these hypotheses without further experimental manipulation.…”