Biological psychology focuses on the physiological causes and explanations of behaviour. Biology is a very important influence on our behaviour but human behaviour is so complex that very little can be explained by physiology alone. The body has an immediate shock response to a stressor, and if the person is exposed to the stressor for some time a countershock response follows. Cognitive Behavioural Therapies offer an especially appropriate psychological method of dealing with stress. Stress is therefore an innate, defensive, adaptive reaction that promotes survival. The example used is typical of the type of stress with which non-human animals have to cope. Segerstrom and Miller point out that it would make no sense in adaptive terms if short-term stress impaired the immune system—after all, it is precisely these conditions that one would expect to result in increased help from the immune system.