by more substantial theories of motivation.
             Psychologists can now use biological and psychological theories of motivation to attempt to determine the drive behind the human instinct. There are several important forms of motivation that include areas such as sexual motivation, aggressive motivation and also hunger and thirst (focusing in this case, on eating disorders).
             A theory of motivation proposed by Abraham Maslow (1970), describes psychological needs such as those for food and water, oxygen and sleep. Maslow refers to these needs as deficiency needs which are essential and must be fulfilled before higher levels of motivation can emerge. These higher levels include esteem needs; self-esteem, the esteem of others and success, and self-actualisation needs (the need to achieve one's full potential). As Baron (1998, p. 387) notes, some results suggest
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