Temperament and cognitive flexibility across lemur species

Temperament can shape patterns of individual differences in animal cognition and behaviour. An influential hypothesis proposes that bolder and more exploratory individuals are less cognitively flexible than shy individuals. However, there is also evidence that the relationship between temperament and cognition may vary depending on the particular social and ecological challenges an individual faces. Here, we test the link between temperament and cognitive flexibility by examining seven lemur species (N = 65) with targeted variation in diet and social organization: Coquerel's sifakas, Propithecus coquereli, ruffed lemurs (Varecia spp.), ringtailed lemurs, Lemur catta, mongoose lemurs, Eulemur mongoz, collared lemurs, Eulemur collaris, crowned lemurs, Eulemur coronatus, and blue-eyed black lemurs, Eulemur flavifrons. We assessed temperament by measuring responses to novel objects and persistence in trying to obtain an inaccessible reward and indexed cognitive flexibility in a reversal learning task. This allowed us to compare species' responses as well as inter-relationships between temperament and cognitive flexibility across individuals. First, we found notable differences in both temperament and cognitive flexibility in these species. For example, frugivorous ruffed lemurs and folivorous sifakas were bolder and more persistent than other species, while sifakas performed worse in the reversal learning task compared to other species. Second, we found that bold individuals who were quicker to approach novel objects were less cognitively flexible across all individuals. However, this pattern could vary by species and measure of boldness: folivorous sifakas who spent more time near novel items were actually more cognitively flexible. Overall, these results provide support for the proposed relationship between bold temperament and reduced cognitive flexibility but also indicate that this relationship can differ across species, highlighting the importance of considering how socioecology may shape the link between temperament and cognition.