The holism-reductionism debate examines how different psychological phenomena should be examined, in terms of the components that contribute to the behaviour we can see. Reductionism believes that in order to understand something fully, it is necessary to reduce it down to its basic components to gain the most fundamental understanding of it (parsimony). There are levels of explanation, which refer to different factors that can be used to explain behaviour, varying in how reductionist they get. The highest level is social & cultural explanations of reductionism, which refers to how society and culture can influence our behaviour (example, they are behaving this way because the law tells them to, or their religion tells them to). This is the least reductionist. The middle level is psychological explanations, which refers to different psychological approaches that could be used to explain behaviour (example, they are behaving this way because they have been conditioned to). Environmental reductionism would fall on the middle layer, due to the fact it explains behaviour through stimulus-response. The lowest level is biological explanations, which refers to how different biological aspects may influence behaviour (example, they are behaving this way because of their hormones). This is biological reductionism.