Personality Test. Portrait of an ISTJ. As an ISTJ, your primary mode of living is focused internally, where you take things in via your five senses in a literal, concrete fashion.
Your secondary mode is external, where you deal with things rationally and logically. ISTJs are quiet and reserved individuals who are interested in security and peaceful living. They have a strongly-felt internal sense of duty, which lends them a serious air and the motivation to follow through on tasks. Personality Tests.