Book: My True Type, page 79 - 85

• Primary roles: To retain, condense, and recollect information; to consult past experiences, routines, and traditions; to perceive inner bodily sensations
• Most prominent in: ISTJs & ISFJs; also prominent in ESTJs & ESFJs
• Associated with: Routines, habits, valuing and preserving “the tried and true,” material conservativism, high regard for traditions and authority
• Famous ISJs: Dick Cheney, Martin Luther, Mother Theresa, George H.W. Bush

Si is more interested in the routine and familiar. It is a careful and conservative function, drawing on existing resources, beliefs, or practices in lieu of exploring or developing new ones.

ISJs take their responsibilities seriously, down to the last detail.

Reference

Book: My True Type Clarifying Your Personality Type, Preferences & Functions Copyright © 2014 A.J. Drenth