Do Cleaner Fish (Labroides dimidiatus) Have General Cognitive Ability? A Reanalysis of Individual Differences Data and Consideration of Phylogenetic Context

Aellen et al. (2022) recently suggested on the basis of principal component analysis (PCA) that there is no general cognitive ability (GCA) factor in various cognitive ability measures of wild-caught cleaner fish (Labroides dimidiatus), making this species an oddity—given the apparent ubiquity of this dimension in many animal taxa. They report the presence of three approximately co-equal factors instead, with the first exhibiting a mixture of positive and negative loadings. Reanalysis of their data employing unit-weighted estimation yielded a GCA factor with all positive loadings accounting for 29.9% of the variance. Adding a fourth ability (feeding against preference) yielded a positive manifold accounting for 19.3% of the variance. As this technique for factor estimation typically yields latent variables exhibiting higher generalisability than those obtained via differentially weighted techniques (such as PCA), it is suggestive of what might be found were sample specificity effects to be reduced via more extensive sampling of individuals. Consistent with this possibility, it is found that the proportion of variance associated with unit-weighted estimated GCA in these data is not significantly different from the proportion of variance associated with this factor in a meta-analysis of 12 other animal taxa. Adaptationist theories of GCA make explicit predictions concerning where in the phylogenetic landscape this factor might be expected to be strongly or weakly present, or even absent altogether. These are discussed in detail.