Thirteen years ago, then-Sen. John Pastore asked: what is the effect of all the violence on television? Nobody, it turned out, knew. His question sparked research that was summarized in a report by the surgeon general in 1972. The findings were preliminary, it said, but there was evidence that extensive viewing of violence led to an increase in aggressive behavior among children, at least over the short term.

During the ensuing decade there was so much research on television's effects, that the surgeon general was asked to review and analyze the mass of published studies. The report issued last week by the National Institute of Mental Health, is the result. It confirms and strengthens the earlier findings. There is now "overwhelming" evidence of a correlation between televised violence and aggression in children. There is also, the report says, a consensus among researchers on a causal relationship, that is, that watching violence on television leads to more aggressive behavior among children and teen-agers.

The research has moved outside the laboratory. Year-long investigations of 3- and 4-year olds correlated the children's behavior during free-play periods at day-care centers with their TV viewing at home. The studies found consistent associations between heavy viewing of violent programs and greater aggression during play. Other studies compared aggressive behavior among schoolchildren before and after television came to their communities. Another, which followed the same children for five years, found the relationship between television violence and aggression expressed in terms of conflict with parents as well as increased fighting and delinquency. Only one study cited in the summary report, sponsored by the National Broadcasting Company, did not find evidence of this connection.

The percentage of programs showing acts of violence has remained about the same since 1967, though the amount of violence per program has increased. Astonishingly, for 10 years, there has been more violence on children's weekend programs than on prime-time television.

If the evidence is as clear as this report says, ways need to be found to reduce the amount of violence on television and to change the ways it is portrayed. Violence is what works, on television: the good guys win by casually killing a few folks, having an automobile chase in which anything or anybody unlucky enough to get in the way gets smashed, and ending by forcing someone to jump off a cliff.

Government regulation is not the answer. The national networks bear the heaviest responsibility; they dominate the airwaves, and their shows echo for years on reruns on other channels. The networks do respond to public pressure. As one producer put it, "The way to get more and better television programs is to have people insist on it...Very definitely, pressure groups can work."