Behavioural observation and self-monitoring is a necessary tool for assessment in order to get a good picture of an individual's actual behaviour as opposed to their thoughts and feelings. What an individual says in clinical interviews may not correlate with the behaviour they're presenting due to recall error, culture, or bias; therefore, behavioural observation can fill in missing information for a full assessment and diagnosis.
Observation of an individual's behaviour can occur through participant observation, which involves interviewing the person while also observing their behaviour, and natural or experimental observation. Duration, magnitude and frequency are often used when looking for and recording behaviour. An example of this could be watching someone as they interact with a family member and counting how many times they perform a certain act, or in an experimental condition, giving the individual a task and observing them as they complete it. Behavioural observation is beneficial because it is objective and can be used to make improvement and track the results of a treatment plan.
Image credit: Walt Stoneburner
Self-monitoring can also be used to evaluate behaviour by asking a client to monitor themselves, which can be done through the use of a journal. For instance, an individual might right down every time they have a negative thought about themselves, along with what occurred to make them have this thought. This information can help the clinician determine what may cause the client to have negative thoughts in order to aid with diagnosis and the creation of a treatment plan. The downside to this method is that clients may not be honest with recording all of their behaviours.