Some actions are intrinsic motor units that can be concatenated as needed to solve a problem. In contrast, many actions are correlated with one another when engaging in particular types of behaviour, such as predation, mating or aggression. Moreover, how those actions are associated depend on intrinsic rules of organisation. Consequently, selecting markers to measure as if they are independent may be misleading. For example, scoring success in grasping a piece of food may fail to reveal that different combinations of limb movements may be capable of comparable rates of success. The lack of independence among actions and the potentially misleading conclusions that can be drawn from end-point measures point us to the second principle – understanding the intrinsic organisation of behaviour. Knowing something about the intrinsic organisation of a behavioural sequence can be critical in identifying markers that reflect that organisation.