One of the drollest observers of life in Midwest America, in particular, is Garrison Keillor. He hosts an old-timey type radio variety show called "A Prairie Home Companion."

Keillor also writes a newspaper column, and in one of them recently, he described a canoe trip that he took on the wild and beautiful lakes of his home state of Minnesota. It was the kind of rugged adventure that requires the services of a guide or trip leader.

"Every canoe trip has a self-appointed Master Woodsman," Keillor writes. "In civilian life he may be a mild-mannered clerk in [an office] cubicle, but out on the trail he is transformed into the song leader, pathfinder, the great helmsman, the tier of correct knots and the authority on bears."

Garrison Keillor is describing a variation of what can be called the "uniform complex." Put a uniform ? of a baseball manager, a security guard, even an usher at an opera ? on otherwise meek introverts, and they can turn into belligerent oafs, barking out orders.

This personality transformation ? or whatever the psychologists call it ? happens in the other direction as well. Take-charge executives, used to getting their way, turn into puddles in front of their doctors or priests. Pro football players who knock opponents into paste blubber when a nurse pricks their fingers to draw a drop of blood.

These are temporary or part-time personality changes that aren't pathological. In fact, they're amusing to behold.

Take the mousy store clerk who, at a sporting event, morphs into a ranting, screeching, foul-mouthed critic of every play and player ? even on his own team. So, you see, the process called metamorphosis ? in which ugly nymphs turn into beautiful butterflies and even some rocks profoundly change appearance ? can apply to human behavior as well.