Modern dairy cows appear to be less ‘robust’ or adaptable than in the past, as typified by high involuntary culling and poorer health. This could be addressed by the use of broader breeding goals and breeding indices that include traits that are likely to improve fertility and health. Body energy balance and growth rate in the first lactation are traits that are likely to underlie health and fertility and have been included in an index of robustness (Wall et al., 2006). However, we need to ensure that the inclusion of these new traits does not have any unforeseen effects on animal behaviour, which may reduce the welfare of the individual or the group she is housed in. Selection to improve body condition may mean that the animals seek increased access to feed. It may be hypothesised that this could lead them to be more aggressive at the feed-trough. Alternatively, they may increase their feed intake by becoming unresponsive to the social and physical environment, and feeding outwith the peak feeding period. This could mean that they become less responsive to their environment and possibly become harder to handle. The aim of this experiment was to compare the behaviour of daughters of bulls which scored high on the functionality sub-index of the robustness index (‘high functionality’ bulls) with daughters of bulls which scored low (‘low functionality’ bulls) on this sub-index. Specifically, we investigated the responsiveness to the environment, by assessing reactions to a novel object and to an unfamiliar person.