The target paper sets out an ambitious approach to animal personality research. This approach uses bottom-up measures and behavioural repertoires. This method holds promise for understanding personality trait expression in a given species; however, it has limited applications for comparing personality between species because it does not specify a measurement of interspecific similarity or difference and does not consider phylogenetic relationships between organisms. Our research led its to develop a modified top-down trait approach which makes comparing species feasible, is sensitive to species-level differences and is consistent with evolutionary thinking. Copyright (C) 2008 John Wiley & Sons, Ltd.