Post by Regan MacKinlay & Rachael Shaw
Can a songbird’s song act as a signal of their cognitive ability for listeners? Individual birds produce slight variations on their species’ specific song. Previous research reveals that individuals’ song repertoires are learnt, and that song learning is influenced both by genetics and events during early development. Both genetics and developmental effects have also been shown to influence other cognitive processes. Importantly there is substantial evidence that both complex bird song and cognitive ability are the subjects of sexual selection. Given these links, it has been hypothesised that song complexity may be used by listeners to gauge the general cognitive ability of singers.
Early research indicated the existence of associations between song complexity (typically measured as repertoire size) and cognitive ability in song sparrows (Melospiza melodia). One study found a positive correlation with detour reaching performance (a measure of inhibitory control), and another found a negative correlation with performance on a spatial learning task (a measure of spatial memory). However, a recent attempt to replicate these two studies failed, and in fact found opposing patterns. Re-examining these relationships in a species with a differing ecology to the song sparrow, namely a caching species, may offer a different perspective on the relationship between song complexity and cognitive ability. In a special issue of Intelligence we report that, despite adopting similar testing methodology and sample sizes as previous studies, song repertoire size was not correlated with cognitive performance in spatial memory or inhibitory control tasks in toutouwai (Petroica longipes).
It remains possible that other song features (i.e. besides repertoire size) are correlated with cognitive ability in other domains, but evaluating this will require further research into biologically relevant markers of birdsong complexity. For now at least, it appears that song repertoire is unlikely to be a useful indicator of cognitive ability for song listeners. We therefore recommend that song repertoire sizeshould not be considered a proxy for cognitive ability in song birds.