Summer is here, and again a select group of Americans is suddenly thousands of dollars richer and struggling with the title of "genius."

The 25 recipients of the 1986 MacArthur Foundation grants, the so-called "genius awards," were announced yesterday. Among them are Washingtonians Lester Brown and Thomas Joe, several scientists, two poets, the 1986 Pulitzer Prize winner in music and the magician-investigator, the Amazing Randi.

"I left the house, came back to a message on the machine that said, 'Consider this a priority call,' " magician and paranormal phenomenon investigator James Randi said yesterday. When he called the Chicago number, the man who left the message was out to lunch, so Randi went off to the dentist and called again from there. He got through.

"I almost bit all the instruments in half," he said. "The dentist asked what had happened. I said, 'I just won a quarter of a million dollars.' He said, 'Sure. Okay. Just open your mouth.' He was not impressed."

Others, however, were.

"It's sort of an interesting feeling for someone to call from out of the blue to say, 'You've just been given a quarter of a million dollars,' " said Lester Brown, founder of the Worldwatch Institute.

Indeed.

"All I could say was, 'Gosh!' " said author Thomas Whiteside, 68, of New York, whose reports in The New Yorker on dioxin in Agent Orange contributed to the eventual ban on herbicidal warfare in Vietnam and to restrictions on commercial use of dioxin-contaminated products. "I told him he'd taken my breath away, but I recovered it all right. Obviously, there's a lot of money involved and I'm not used to all that, but I hope to cope with it bravely."

Pulitzer winner George Perle, a professor emeritus of music at City University of New York and an expert on Berg, Schoenberg and Webern, is, at 71, the oldest of the winners. David Conrad Page, 31, is this year's MacArthur baby. A fellow at the Whitehead Institute in Cambridge, Mass., Page has studied what the foundation calls "one of the oldest mysteries of biology: what determines maleness."

The MacArthur awards were created in 1981 to give money away, no strings attached. Scientists, artists, scholars, activists and others have been among the 191 fellows. More than $50 million has been committed, with fellowships beginning at $24,000 a year for recipients 21 or younger. Each additional year in age gets the winner another $800, running up to $60,000 for those 66 or older.

The winners received the news late last week with a call from grants program director Ken Hope. Hope has not yet been able to reach one of the new fellows, Seattle historian Caroline Bynum, who is traveling in Europe. This is not unusual. One earlier winner only discovered his good fortune when his girlfriend, with whom he was vacationing in Texas, read about it in the paper.

The awards carry one particular pressure: the "genius" problem. The description was immediately attached to the program in 1981, despite the protests of organizers and winners.

"Oh, dear," said Thomas Joe, when asked how he felt with the unofficial title. "That's very difficult to absorb. I guess if I was a genius, I would have thought of an easier way of making a living."

Instead, the former special assistant in the Department of Health, Education and Welfare founded the Center for the Study of Social Policy. The "dramatic" phone call from the foundation, he said, made him feel "it's become a major personal responsibility to come up with something equally dramatic to do over the next five years, rather than just passively accepting the money."

Joe, who is blind, specializes in the plight of children and the poor. "Maybe this grant ought to free me to counterbalance this unbalanced debate over the poor, counterbalance the far right. It seems the so-called liberals have not really positively contributed as much as the liberals should . . . "

As founder and director of the Worldwatch Institute, Lester Brown publishes the annual State of the World report, which analyzes trends in the environment, food, population and economics.

"It will not affect what I do," he said of the award. "It will make what I do a bit easier and hopefully help us do a better job with the World report."

Although the nominating and selection process is kept hush-hush, the winners seemed to share a cheery but almost blase' tone about the awards.

For example, composer Milton Babbitt, 70, said he will "probably buy some books." Whiteside said, "I plan to carry on pretty much as I have been while I take stock of things. I consider I took it very well, but about the third day little doubts began to creep in and I wondered if this was real . . . "

But he has recovered.

"The champagne hasn't been flowing," he said. "I feel in a way it's rather important I get a grip on myself and get on with my work and not let this distract me and impede me. After all, it's great, but at the end of five years it will be over and I'll just go on." The other winners:

-- Paul R. Adams, 39, State University of New York at Stony Brook, who works in basic brain biophysics and conducts research on Alzheimer's disease, the prime cause of mental deterioration among adults.

-- Richard Peter Turco, 43, of Marina del Rey, Calif., an expert in atmospheric physics and chemistry who was instrumental in developing the theory of nuclear winter.

-- Jay Wright, 51, of Piermont, N.H., a poet who draws on medieval and Renaissance studies, philosophy, anthropology, music, religion and the literatures of Europe, America and South America to create his verse.

-- Christopher I. Beckwith, 40, chairman of the Tibetan Studies Program at Indiana University, whose work integrates the cultural and economic history of medieval Tibet with that of Central Asia.

-- Richard M.A. Benson, 42, Newport, R.I., a specialist in the preservation of photographic technologies of the past, including the lost arts of palladium and platinum printing.

-- Caroline W. Bynum, 45, history professor, University of Washington, whose work on the relationship between gender and spirituality in medieval life includes often ignored issues such as the role of diet and nutrition in social life.

-- William A. Christian Jr., 42, of Las Palmas de Gran Canaria, Spain, an independent scholar who studies popular religion and Roman Catholic tradition in Spain.

-- Nancy M. Farriss, 48, history professor, University of Pennsylvania, and director of its ethnohistory program, who has studied the impact of European domination on the Mayan nation.

-- Benedict H. Gross, 36, of Harvard University, an authority on number theory and Gaussian integers.

-- Daryl Hine, 50, of Evanston, Ill., is one of the few American poets who earns an income chiefly from writing. He was editor of Poetry magazine from 1968-78.

-- John R. Horner, 40, Montana State University, a paleontologist who in 1978 discovered the skeletal remains of a small dinosaur in an area where others had unsuccessfully searched for dinosaur nests for decades.

-- David N. Keightley, 53, history professor, University of California, Berkeley, who studies oracular inscriptions carved in bone and shell, an important body of 5,000-year-old records from China's Bronze Age.

-- Albert J. Libchaber, 51, University of Chicago, who specializes in nonlinear dynamics, instabilities, turbulence and chaos theory in experimental physics.

-- David Rudovsky, 43, of Philadelphia, a civil liberties activist, attorney and educator.

-- Robert M. Shapley, 41, of Rockefeller University in New York, whose research in vision science has altered the conventional understanding of how humans see.

-- Leo Steinberg, 66, Benjamin Franklin professor of history of art, University of Pennsylvania, has written on painting, sculpture and architecture of the Renaissance, baroque and modern periods.

-- Allan C. Wilson, 51, biochemistry professor, University of California, Berkeley, analyzed the structure of proteins to discover a steadily ticking "evolutionary clock" used to trace evolutionary development.

-- Charles Wuorinen, 48, music professor, Rutgers University, a composer, conductor and pianist who is currently composer in residence with the San Francisco Symphony.