So I am teaching kindergarten summer school and have run in to an "issue" with one of my little girls. It is frequent and somewhat disruptive. The parent was no help...so I was doing some research to figure out how to deal with this issue. Little did I know....
Physiologic signs of sexual arousal occur in all children from very early infancy onward. This arousal can happen randomly, in response to physical stimulation, or during the dream phase of sleep. There is evidence that even very young infants find the physical sensation of sexual arousal emotionally pleasurable, and most children will learn how to create this feeling in themselves by the preschool years. Indeed, by the age of 5 or 6 repeated, systematic, intentional masturbation is almost universal! There is some debate over HOW children learn to masturbate. Some think it is initially an accidental or random phenomenon - as the young child explores their own body they by chance discover that touching certain areas feels better than touching others, so they are motivated to touch those places again. Others feel this discovery is more likely related to some discomfort in the genital area which draws the child's attention - such as a diaper rash. It really doesn't matter how it gets started however - once begun, the behavior perpetuates itself.
There is nothing inherently harmful to the child about masturbation itself. It neither causes nor is a sign of any physical or emotional problems whatsoever. The best evidence for this comes from cross-cultural studies which have looked at masturbation and other aspects of sexual development in societies where both adult sexual activity and masturbation are more accepted and "public" than in our own. In these places children are routinely witness to normal adult sexual behaviors, and they in turn they do indeed masturbate more, earlier, and incorporate sexual themes into much of their play among each other as well. It turns out that, if anything, these cultures have lower rates of sexual dysfunction, of deviant sexual behaviors, and family disruption than we do here in western cultures. There are, however, three issues related to masturbation that parents should be aware of and think about: The first is how their own reaction to the discovery of a child's masturbation may affect the child. The second is how masturbation fits into their larger job of teaching children socially appropriate behavior. The third is the need for sensitivity towards what the meaning of the masturbation is to the child, and to what that in turn might signify regarding the normalcy of the child's other sexual experiences and ideas.
In summary, masturbation is a normal and harmless behavior in childhood even at a very young age. It is important that as a parent you not react too strongly to it, and that you avoid disciplining, repressing, or making your child feel guilty about it. On the other hand, you do have a responsibility to teach your child to limit this behavior to an appropriate time and place. Occasionally (but not often) masturbation can be a sign or symptom that a child is under undue stress or has been sexually abused. Should such a situation ever arise, your child needs you to focus on and address the root problem, not the symptom of masturbation, in order to really help them.