AT AGE 23, Everett Alvarez was one of the first Americans to be taken prisoner in Vietnam. He spent almost a decade in POW prisons, often in solitary confinement in which huge rats scurrying in his cell was the only sound he heard. His daily ration often was a chicken head floating in grease.

Uncontrollable diarrhea and high fevers dehydrated and emaciated him. After his sixth year as a POW, his captors gleefully delivered a devastating letter: Alvarez's wife had left him for another man. Now for Alvarez, there was not only no present but no future as well.

Popular and professional psychological wisdom would suggest that Alvarez should have never recovered. But here are the facts: Everett Alvarez, now remarried, lives with his devoted wife and two handsome sons outside of Washington. Recently graduated from law school, he serves as deputy administrator of the Veterans Administration. He is a contented and beloved husband and father.

The story is worth remembering as we await the return of the hostages held in Lebanon. Once again, "experts" are offering the public their forbidding prognoses, reading into the televised images of the hostages' suffering faces the seeds of lifelong psychological scars.

It is the same refrain we heard prior to the release of our hostages from Iran. According to popular expectations, these 52 men and women should have become the victims of lifelong emotional problems. For months prior to their release, we heard mournful prognoses on national television: "permanent problems in interpersonal relationships . . . permanent coordination difficulties . . . permanent damage to memory."

No such forecasts have been realized. The lesson is that -- assuming hostages physically survive -- some endure the emotional reverberations that are naturally evoked by stress. But lifelong emotional cripples? Hardly.

For over three decades, I have studied victims of overwhelming trauma -- concentration- camp survivors, POWs liberated from years of captivity, terrorized hostages, bewildered refugees. Repeatedly, I have been inspired by the countless cases that run counter to widespread predictions. Instead of a pattern of deficit and defeat, there is one of coping and conquest.

Indeed, rather than being devastated by their suffering, many survivors have actually used the experience to change their lives in ways they see as beneficial.

Former Iranian hostage Moorehead Kennedy, now executive director of the Council on International Understanding, was asked what he thought might lie in store for the hostages who hold the world's stage today. "I came out of the hostage experience a very different person," he answered. "My wife said, 'One Kennedy went over there, and another came back.' She rather preferred the one that came back.

"It brought out of me things I didn't know I had. I wouldn't recommend it -- but I'm glad after the event that I went through it. Every one of those hostages will learn something from the experience."

Our POWs in Vietnam endured separation, starvation, dysentery, parasitic infestations, humiliating interrogations, torture, and solitary confinement. Yet, by and large, their psychological status remains surprisingly sound.

True, the American POWs in Vietnam were older and more mature than the typical soldier, and they were well trained and highly motivated. But who can say what untapped well of resiliency any one of us might draw on when the chips are down? Says former hostage-diplomat Bruce Laingen: "We're like tea bags. We don't know our strength until we get into hot water."

Many of us tend to believe we could never muster what it takes. Capt. Richard A. Stratton, now director of the Naval Aademy Preparatory School in Newport, R.I., lived through six savage years as a POW in Vietnam. Stratton has spoken to thousands of groups since his return from captivity. "In every group," says Stratton, "there is an unspoken question in the minds of my listeners. 'I wonder if I could do it.' And the silent answer is: 'I don't think I could.'"

"People say to me," observes Alvarez, "that they don't know how I did it. 'Gosh,' they say, 'I never could have gone through those 81/2 years.' And I say to them, 'If I could do it, you could, too.' People just don't give themselves enough credit."

As a psychologist, I admit that my own profession has been responsible to a degree for our self-defeating tendency to live scared -- to expect to crumble in the face of crisis rather than to surmount it. For many decades, we have concentrated our efforts on trying to learn why some people break down under stress, not how they might overcome it.

We have directed our energies, says University of Minnesota psychologist Norman Garmezy, to "the study of patterns of maladaptation and incompetence." The reason, he says, is that "our mental health practitioners and researchers are predisposed by interest, investment, and training in seeing deviance, psychopathology, and weakness wherever they look."

All but ignored have been the vast number of people -- most of us, I believe -- who are able to endure and to live triumphantly despite crushing stress. Indeed, until recently, the human capacity for endurance appears to have been one of psychology's best-kept secrets.

I do not deny, of course, the threat to our hostages' physical well-being. Nor do I say that the kind of excruciating stress they have endured does not have the potential for harm. Researchers have carefully detailed how disturbing life events can leave us with anxiety, depression, high blood pressure, heart attacks, bronchial asthma, colitis, and stomach ulcers that can plague some trauma victims for years.

But I do reject the assumption given currency by many in my field that such psychologically induced problems are inevitable or universal -- that they are penalties we must all pay.

Studies even of concentration- camp survivors -- the ultimate victims -- show that, contrary to popular assumption, many have adapted surprisingly well in the years beyond their ordeal. The findings of a recent study of Holocaust survivors now living in Montreal, for example, focus attention on what the authors describe as "the magnificent ability of human beings to rebuild shattered lives, careers, and families, even as they wrestle with the bitterest of memories."

Buried in the human breast are undreamed-of powers of healing and even growth in the face of stress. The testimony of survivors is clear enough: We are rarely as fragile as we imagine ourselves to be. In the psychological destiny of those Americans held captive, there undoubtedly awaits a message for us all.