Firstly are the observable behaviours which are clearly recognized by the external forces like anger, shyness etc. others. People can easily observe these behaviours in the activities done by individuals. Emotional behaviours are often used to enable a person adjust into particular situations. It is mainly used to reduce the level of anxiety in the behaviour of an individual. This can reduce the level of anxiety in short run but in long run it is not useful. Subjective behaviour of an individual is the kind of behaviour which is not observable by others easily. It includes the perceptions an individual makes about certain things and situation (Nicol, 2006). The intrinsic values of a person are the major factors which derives the behaviour of an individual. The feeling and thoughts of an individual about a particular situation is a very confidential matter and an individual does not clearly show these kinds of emotions in his behaviour in general. The last level is psychological behaviour, it relates to the increase in heart beat if something wrong happens, sometimes sweating if a person is emotionally feeling low or in the state of fear of something. The target behaviour is Excesses and emotional behaviour related to nervousness. The nail biting behaviour occurs at high frequencies with high intensity with long duration and is problematic to the situations in which they occur. The FBA (Functional Behavioural Assessment) analysis will be done with keeping in mind the reoccurring behaviour of nail biting.