Psychology thumb|left|upright|World War II era employment poster about the importance of fun According to Johan Huizinga, fun is "an absolutely primary category of life, familiar to everybody at a glance right down to the animal level." Psychological studies reveal both the importance of fun and its effect on time perception, which is sometimes said to be shortened when one is having fun. As the adage states: "Time flies when you're having fun".
Psychology thumb|left|upright|World War II era employment poster about the importance of ?fun According to Johan Huizinga, fun is "an absolutely primary category of life, familiar to everybody at a glance right down to? the anima,l level." Psychological studies reveal both the importance of fun and its effect on time perception, which is sometimes said to be shortened when one is having fun. As !the adage states: "Time flies when you're having fun".