Figure 1.

Causes and consequences of individual variation in the microbiome in relation to environmental and developmental effects, and the subsequent impact on neurological, cognitive and behavioural traits. Arrows indicate potential causal directions of relationships and are not exhaustive (for example, development may directly affect cognition independent of microbiome). Italics refer to selected phenotypes that have yet to be investigated empirically (i.e. animal personality) and where null results have been found (i.e. social information transfer [18]).