sentences:  Switching to a direction is symbolized by the act of putting on a colored hat, either literally or metaphorically.This metaphor of using an imaginary hat or cap as a symbol for a different thinking direction was first mentioned by De Bono as early as 1971 in his book "Lateral Thinking for Management" when describing a brainstorming framework.These metaphors allow for a more complete and elaborate segregation of the thinking directions.