There are some interesting moments in tonight's "Nova" (Channel 26 at approximately 8), not the least of which is "young Itzhak Perlman from Israel" appearing on "The Ed Sullivan Show" in 1959, playing (with extraordinary beauty) the last movement of the Mendelssohn E Minor Violin Concerto.

"Child's Play: Prodigies and Possibilities" is the title of this program, which deals with the phenomenon of prodigious achievement in very young children and whether it is a result of, as the researchers say, "nature or nurture."

Indeed, although child geniuses are documented as far back as anybody has been documenting, there is still not a whole lot of hard knowledge about how they got that way. Specialists, including the late neurophysiologist Dr. Norman Geschwind of Harvard, speculate about the various influences on early genius -- cultural, genetic, physiological, sociological.

Geschwind, in what is certainly one of his last appearances before his death last year, discusses his hypothesis that the sex of the fetus may influence brain structure and either enhance or inhibit certain special skills. For example, the testosterone produced by a male fetus may tend to emphasize development of the right side of the brain, where spatial, mathematical and musical skills may be enhanced. But, Geschwind warns, so might be a tendency to childhood dyslexia.

Others suggest that cultural and social factors are required for genius to surface. Violinist Perlman and his wife Toby, for example, discuss his childhood and his mother's influence. Says Toby Perlman, "Your mother believed in you, and she thought you were a great genius. It didn't matter that nobody else believed in you, that you couldn't get concerts, that nobody would help you. She knew you were great and she conveyed that to you . . ." The irrepressible Perlman says, "Oh, I see. In other words you don't think I'm unusual."

The cultural impact is also noted by pianist Lorin Hollander, who admits that after he'd brought a bit of Bach to a grade-school circus, he was roundly beaten up on the playground by his peers.

"Child's Play" has no conclusions to offer, but it is a provocative look at an always fascinating subject.