Behavioral measures are of particular value in welfare assessment; some behaviors such as stereotypies, lack of or normal responsiveness, and excessive aggression being direct indicators of poor welfare. They are especially important when the welfare problems are of long duration. In addition, the behavior of animals is also needed to interpret other welfare measures such as adrenal cortex activity and some aspects of brain function. The various strategies for coping with adversity are usually identified by their typical behavioral components. As a result of the diversity of coping methods, in most scientific studies of animal welfare, a combination of behavioral and other measures is needed. The strength of preferences of animals, for or against resources or environmental impacts, is best indicated by indices of demand, such as the consumer surplus, that are assessed using behavioral experimental studies.