Thank you for the request.
It is possible, to a certain extent, to predict another person's behavior. How successful you will be in predicting behavior is in direct proportion to how much you know about the person, if you have been exposed to their behavior prior and the circumstances.
Social scientists have found that the best way to predict a person's behavior is to observe them in similar circumstances first. Once you learn their behavior patterns, it is easier to understand how they may respond in another scenario.
Although this is a good way to predict behavior in similar circumstances, it does not take in account the unconscious motivations, emotions and learned traits of the person. Each person's behavior is guided by previous experiences included learned and observed. Also, a person is born with a personality. Learning about who a person is is just as important in predicting how they will react in any given situation.
There are many schools of thought that have their own theories of how to predict behavior. For example, Behaviorism theory says that a person becomes who they are through conditioning. This belief system or school of thought is the most radical in terms of their claims of predictability. XXXXX XXXXX, a pure behaviorist, said that he could turn human beings into whatever was asked of him simply by providing a controlled environment. To him, human choice was a matter of reinforcements and there is no free will.
Most modern theorists view predictability as somewhat as a gamble as free will does come into play in each scenario. For example, say I watch you go to work on the same route each day so I predict you will always take that route. Then one day you do not. Human free will is the cause. People get bored, distracted or life circumstances will cause people to choose a different option. Even animals are not as predicable as most people think. Their behavior is guided by the same factors as humans are.
There is some success with predicting behavior using brain scans. A study done at UCLA in 2010 used brain scans to try to predict whether or not someone would use sunscreen in a particular scenario. The scientists were able to predict accurately 75% of the time. But further study is needed to see if using brain scans is a viable option in certain circumstances. Obviously, it would not be practical in day to day life.
I hope this has helped you,