Testing whether sex and size contribute to among-individual
variation
To assess the extent of the contribution of sex and/or size to the
among-individual variation in behaviour, we refitted all models
described above but with additional fixed effects of sex (a 3 level
factor: male, female, unknown), size (mass as a covariate) and their
interaction sex:size. Using univariate models and conditional F-tests,
we tested the significance of these effects on each trait. We compared
estimates of VI and R from these expanded models to
those obtained above. We then refitted our multivariate model with the
additional fixed effects and estimatedIDsex:mass , the among individual (co)variance
matrix conditional on sex and mass. We scaled covariances to
correlations, and subjected IDsex:mass to eigen
decomposition as described above, allowing us to compare its structure
to ID . We also checked for any clustering of personality
visually by sex and/or size in a multivariate personality space, by
predicting and plotting individual scores onidmax for each shrimp.