As we saw in Chapter 1, one of the assumptions of science is that different disciplines are related in a hierarchical way varying from high level sciences at one end, such as sociology, which deal with large units of analysis, to low level sciences at the other, such as physics, which deal with small units of analysis. Thus, a possible ordering might be: sociology, psychology, physiology, chemistry, physics. What is relatively molecular for the high level scientist is relatively molar for the low level scientist. At each level the scientist makes assumptions about that which is the business of the scientist at the next level down. For example, the sociologist, when theorising about the economic behaviour of a society or the language of a culture, makes assumptions about individual people's motivations and acquisition of language; the psychologist, when theorising as opposed to merely observing, makes assumptions about what goes on inside the organism. 'Behavior is made up of hunches about how the nervous system operates to generate the lawful relations that the psychologist observes between stimuli and responses' (Osgood, 1956). There are also different levels of description within each discipline: explanations may be relatively molar or molecular. In psychology, a response may be related to the role it plays in a larger unit of behaviour or to the muscular movements of which it is composed.