Heritabilities and co-variation among cognitive traits in red junglefowl

Abstract

Natural selection can act on between-individual variation in cognitive abilities, yet evolutionary responses depend on the presence of underlying genetic variation. It is, therefore, crucial to determine the relative extent of genetic versus environmental control of these among-individual differences in cognitive traits to understand their causes and evolutionary potential. We investigated heritability of associative learning performance and of a cognitive judgement bias (optimism), as well as their covariation, in a captive pedigree-bred population of red junglefowl (Gallus gallus, n > 300 chicks over 5 years). We analysed performance in discriminative and reversal learning (two facets of associative learning), and cognitive judgement bias, by conducting animal models to disentangle genetic from environmental contributions. We demonstrate moderate heritability for reversal learning, and weak to no heritability for optimism and discriminative learning, respectively. The two facets of associative learning were weakly negatively correlated, consistent with hypothesized trade-offs underpinning individual cognitive styles. Reversal, but not discriminative learning performance, was associated with judgement bias; less optimistic individuals reversed a previously learnt association faster. Together these results indicate that genetic and environmental contributions differ among traits. While modular models of cognitive abilities predict a lack of common genetic control for different cognitive traits, further investigation is required to fully ascertain the degree of covariation between a broader range of cognitive traits and the extent of any shared genetic control.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Keywords: affective state; animal cognition; cognitive judgement bias; cognitive repeatability; heritability; learning.

Figure 1.

Relationship between learning speed in discriminative and reversal learning tests in red junglefowl chicks. Learning speed is measured as trials until criterion reached (hence higher values indicate slower learning; see main text for further details). Each point represents an individual bird. Grey line marks equal speed in the two tasks. Asterisk (*) symbolizes significant value.

Figure 2.

Variance components and heritability for performance of red junglefowl chicks in cognitive tasks. (a) Learning speed in a discriminative learning test, (b) learning speed in a reversal test, (c) approach probability to ambiguous cues, (d) approach latency to ambiguous cues. Stacked bars show, from bottom to top: residual variance, permanent environmental effects variance (limited to judgement bias), additive genetic variance (h², grey bars). Estimates for approach probability are on the latent scale (logit). Asterisk (*) symbolizes significant values.

Figure 3.

Relationship between performance of red junglefowl chicks in various cognitive tests. Associations between: (a) learning speed in a discriminative learning test and approach probability to ambiguous cues, (b) learning speed in a discriminative learning test and approach latency to ambiguous cues, (c) learning speed in a reversal task and approach probability to ambiguous cues, (d) learning speed in a reversal task and approach latency to ambiguous cues. Learning speed is measured as trials until criterion is reached. Points represent individual best linear unbiased predictors (BLUPs) estimates from bivariate mixed models. Correlations were calculated from model 2 × 2 covariance matrixes of individual random effects. Significance (*) was assessed via LRT.