playing 'doctor'

yesterday i walked in on my 7 yo son and his friend also 7 and my 4 1/2 old son playing in the bedroom with their shirts off.  they said they were doing the "belly dance" and i explained that this is not the way we play and everyone get dressed and go downstairs.  later my 4 yr old said that they had all their clothes off at one point and the friend was the "doctor" and he looked at their privates and their bottoms.  i told both boys (the friend had already gone home) that this was unacceptable and my oldest would have no playdates the rest of the week.  i'm wondering, though, if this is a normal behavior or something i should be concerned about.  my son said his friend had the idea, but i don't know if this is the truth. not that it really matters whos idea it was.  this happened once before with another friend and his little brother although playing doctor was not involved, just dancing around naked.  my son also said the other child had the idea to play that game.  i know kids lie to get out of trouble sometimes and we had serious discussion about that.  i'm just wondering how concerned i should be about this and if it is something kids this age just do.

[Kevin Kennedy, Ph.D.]

This sounds innocent enough, and is not unusual for children of this age. Keep an eye on things, and when they have friends over be sure to watch carefully and have them keep the door open. Also, be sure to inform the parents of the other child, if you haven't already done so. And be sure to be specific about what you expect - i.e., that the children are to keep their clothes on and they are never to touch the genitals or buttocks of another child nor allow others to touch them.