What was going on when I was born?

The economic summit ended on a hopeful note, with the seven world leaders ''now clearly seeing signs of recovery.'' Without being specific, the final communique called for steps to reduce inflation, interest rates and budget deficits. In a tradeoff, the leaders agreed to the possibility of a conference on monetary changes, a French goal, and said budget deficits should be cut through lower expenditures, the Reagan view. (Page A1.)

Sexologists are struggling to enhance the scientific credibility and public acceptance of their research at a time when sexual studies and sex education in this country are under increasing attack. This became clear last week when more than 1,000 sexologists convened here for the sixth World Congress of Sexology, billed as the largest gathering of sexologists ever held. Speakers and panel chairmen repeatedly lamented that their field is suffering from a conservative political backlash that often portrays sex research and education as little more than pornography and sex therapy as almost illicit. The organizers tried unsuccessfully to get official welcoming messages from the White House and the Mayor's office, ordinarily a routine courtesy, but neither political office would oblige. ''They said it was inappropriate,'' complained William A. Grantzig, president of the organizing committee. ''This is not porn city. Some of the talks are even boring.''

After three days of negotiations at the ninth annual economic summit conference, a profound gridlock over economic policy is apparent. The leaders of the major industrial nations came here to deal with one overriding issue: how to sustain economic recovery but avoid a new outburst of inflation. They will depart on Tuesday having agreed to maintain economic recovery, to reduce inflation, interest rates and unemployment and to ''roll back'' protectionism - but generally without specific proposals to accomplish these goals. As Prime Minister Margaret Thatcher of Britain, who left Sunday night, ruefully conceded, ''We all condemn protectionism, but almost every country practices a certain amount.''

The officers who patrol the highways here know well that there are four holidays more ominous than all the rest - Memorial Day, the Fourth of July, Labor Day and the Christmas-New Year's period. ''Christmas you get drunks,'' said James McGarry, a Suffolk County highway patrol officer who has worked the Long Island Expressway for more than a decade. The Fourth of July has the overheaters. The Labor Day rush-hour crowd is cranky. ''It's the end of the season,'' Patrolman McGarry said, ''and everyone thinks he can make it home in an hour and a half.''

The Soviet Union's rigidly centralized economy is likely to muddle through the 1980's at a low growth rate but without danger of collapse, according to a Central Intelligence Agency analysis released today. At the same time, the agency said there appears to be little chance the Kremlin will undertake the kind of radical reforms that could unfetter economic decision making and improve the lot of Soviet consumers. While the average growth in the gross national product could reach as high as 2 percent, an improved economic performance is not expected without major policy changes.

Ten years ago this month, Terry E. Herndon became executive director of the National Education Association at the age of 33. This week, still young enough to try a new career, he is leaving the organization to try his hand at other fields. In an interview in his office, just a few blocks from the White House, Mr. Herndon reflected on the changes he helped bring about in the organization, which serves as a professional society and union for 1.7 million educators, and on some of the problems still facing the nation's public schools. Q. Are you leaving because of what has become known as ''teacher burnout?'' A. Well, it has been a hectic pace. I have spent virtually all my adult life as a leader in this organization. It was fortunate in one way that I was able to do this in the early part of my life. But I think it's counterproductive for anyone to try to lead a political or quasi-political institution for 25 or 30 years. I came to the conclusion that it would be good for me personally, and good for the N.E.A., if there were a change at this time. But I have no regrets at all. It's been a great 10 years.

After months of indecision over awarding the largest military contract to an outside supplier in Spanish history, the Government has decided to go ahead with the purchase of F-18A fighter planes from the McDonnell Douglas Corporation, Prime Minister Felipe Gonzalez announced today. In a cost-cutting move, however, the number of planes has been reduced to 72, from the 84 originally contemplated, a decision criticized by the Spanish Air Force. The choice of the American producer signaled a failure for an intensive lobbying effort by European manufacturers to lure the Government away from the $3 billion deal, especially a British-West German-Italian consortium that produces the Tornado multi-combat aircraft. The McDonnell Douglas purchase was originally negotiated in July by the former centrist Government of Leopoldo Calvo Sotelo. The new Socialist Government signed a letter of intent to follow through on it in December and paid $8.4 million in nonrefundable down payments to maintain the purchase price and delivery schedule.

International Greater unity in economic policies and more consultations to deal with erratic currency exchange rates that have battered West European economies were pledged by the leaders of the major industrial democracies. The seven Government leaders, ending their three-day summit conference in Williamsburg, Va., also said that further steps were needed to reduce trade barriers, narrow budget deficits and lower both inflation and interest rates. (Page A1, Cols. 4-6.) The P.L.O. leadership warned that its forces would strike back if any rebels in Al Fatah, the main Palestinian guerrilla group, tried to seize any of its installations in Lebanon. But a senior aide to Yasir Arafat, chairman of the P.L.O., said the organization ''will not use arms against anyone in Damascus,'' where six Fatah supply depots have been seized. (A1:3.)

When it opened in 1951 on a bend in the Delaware River 30 miles north of Philadelphia, the United States Steel Corporation's Fairless Works created some 7,400 jobs, drawing thousands from depressed coal mining towns in upstate Pennsylvania and elsewhere. Many towns grew in its shadow, among them Levittown, Pa., whose 17,300 look-alike homes make up the world's largest, and most studied, planned suburban community. The plant, with nine huge open hearth furnaces, was a model of postwar industrialization: A facility where steel was actually produced, as well as ''finished'' -shaped into final products such as beams or rails. But the open-hearth method has become outdated, lower-priced foreign imports are threatening and now the future of the plant, along with that of thousands of workers and the economy of lower Bucks County, hangs in the balance.

It takes two musician-hours to play a Mozart quartet. This is exactly the same as was required two centuries ago when the work was written. The modern technological era has brought higher and higher productivity to many fields, but live concerts are one activity where virtually no such growth could be achieved. Now two economists, William J. Baumol of Princeton and New York Universities and Edward N. Wolff of New York University, propose that productivity growth may be ending for many sectors of the nation's economy, including some areas of high productivity growth such as computer services. Productivity is a measure of how much people produce for each hour they work. Economists often measure this output in terms of its dollar value.

''We have strengthened our resolve to deal cooperatively with continuing problems so as to promote a sound and sustainable recovery, bringing new jobs and a better life for the people of our own countries and of the world.'' - From the Williamsburg Declaration on Economic Recovery. (A1:6.)

Some morning soon, it's going to be Code Red in the ant colony. There will be a huge explosion of liquid hydrogen and oxygen and solid fuel beneath the unsuspecting ants, hurtling them 180 miles into the air and flinging them around and around the earth at 17,500 miles an hour. Gravity will be lost. What will happen to the them biologically and to their sophisticated social structure, no one knows - which is why they are being sent into space. Tucked into the cargo bay of the space shuttle Challenger, among the communications satellites of Canada and Indonesia, the classified experiments of the Air Force and the cosmic radiation experiments of the National Aeronautics and Space Administration, will be the 150 carpenter ants from Camden. Ants in space is the idea of Camden high school students, and their experiment has been deemed important enough by NASA to qualify for its Small Self-Contained Payloads Program, open to those with scientific research projects and the $3,000 to $10,000 fare.