Narrator: This is Science Today. Playtime should not be just for kids. Adults, for psychological reasons, need to continue playing past their childhoods. Lenore Terr, a clinical psychiatrist at the University of California, San Francisco, believes play is one of the three essentials of adult life.

Terr: Freud had been asked many, many years ago what made a normal adult and Freud said, "the ability to love and to work." Now that was 19th Century Vienna talking and in 21st Century America, we have to say to love, to work and to play.

Narrator: And that doesn't just mean sports. Play can be defined as anything done just for the fun of it - including work, dancing, painting, or reading. Play can give people fulfillment, make them more flexible and Terr says it could even save some marriages.

Terr: I think that a lot of marriages fall apart because the play aspect of the marriage isn't good enough. It is difficult because men and women play differently and that they traditionally have different ways of playing. I think that in some marriages, they have to compromise and find some ways of play that they both enjoy.

Narrator: For Science Today, I'm Larissa Branin.