You use all four mental muscles - Sensing, iNtuition, Thinking and Feeling - irrespective of what is written in your four letter code. However, according to Jung's theory, you are born with a preference for using certain mental muscles more than others. You will therefore exhibit all the behaviours listed on this slide at some time or other - the important question (from the Myers Briggs perspective) is "what is your inborn preference?"

Bad Joke: Heredity is something people believe in if they have a bright child.