General cognitive performance declines with female age and is negatively related to fledging success in a wild bird

Abstract

Identifying the causes and fitness consequences of intraspecific variation in cognitive performance is fundamental to understand how cognition evolves. Selection may act on different cognitive traits separately or jointly as part of the general cognitive performance (GCP) of the individual. To date, few studies have examined simultaneously whether individual cognitive performance covaries across different cognitive tasks, the relative importance of individual and social attributes in determining cognitive variation, and its fitness consequences in the wild. Here, we tested 38 wild southern pied babblers ( Turdoides bicolor ) on a cognitive test battery targeting associative learning, reversal learning and inhibitory control. We found that a single factor explained 59.5% of the variation in individual cognitive performance across tasks, suggestive of a general cognitive factor. GCP varied by age and sex; declining with age in females but not males. Older females also tended to produce a higher average number of fledglings per year compared to younger females. Analysing over 10 years of breeding data, we found that individuals with lower general cognitive performance produced more fledglings per year. Collectively, our findings support the existence of a trade-off between cognitive performance and reproductive success in a wild bird.

Cognitive performance is linked to fitness in a wild primate

“…Thus, potential age effects in cognitive performance should be treated with caution because only few individuals reach such an old age in the wild; we tested overall only four individuals older than 5 years. A decline with age in a general cognition factor has also been reported in female Arabian babblers (26). Because older females produced more fledglings, there might be a trade-off between cognitive performance and reproductive success in this species (26).…”

“…A decline with age in a general cognition factor has also been reported in female Arabian babblers (26). Because older females produced more fledglings, there might be a trade-off between cognitive performance and reproductive success in this species (26).…”

“…*Corresponding author. Email: claudia.fichtel@gwdg.de (Turdoides bicolor), variation in a general intelligence factor did not predict reproductive success (26,35). In other studies, performance across cognitive tasks did not positively correlate with each other, indicating that the used cognitive tasks addressed abilities in different cognitive domains (36,37).…”

“…Thus, differential fitness resulting from heritable variation in cognitive performance suggests that cognitive traits can evolve (22). However, in other studies, no or a negative link between cognitive performance and one of these fitness proxies has been reported (18,(23)(24)(25)(26). This outcome might be due to the fact either that there is a trade-off between the energetic costs of enhanced cognitive abilities and somatic maintenance or reproduction (23,(26)(27)(28) or that the applied cognitive tests did not capture ecologically relevant cognitive traits (21).…”

“…In principle, selection may act upon different cognitive abilities separately or jointly as part of a general cognitive ability (7,26). The presence of a general intelligence factor (g) has been suggested for humans, but its existence remains debated in animals (29)(30)(31).…”