Travel, according to the old saw, is ''broadening.'' By that yardstick, Americans should be developing en masse the beam-shouldered countours of linebackers in the National Football League. Our airline mileage is astronomical. Our servicemen are on patrol from the Caribbean to once-exotic harbors in the Indian Ocean. Buses compete with motorbikes, campers, and Amtrak trains to swarm over our native landscape.
Yet the results of all this movement are questionable. We all know people who , despite constant changes of locale, remain firmly restricted in outlook. On any venture beyond their accustomed haunts, they load up their suitcases with the protective insulation of magazines and stereo cassettes - and their heads with rigid preconceptions. No matter what the destination reads on their plane tickets, for all practical purposes they never leave home.
Conversely, we know others who not only luxuriate in foreign waters but seem able to fashion a glorious romp out of a trip to the supermarket ... like the naturalist friend who last spring whisked me from my Santa Barbara apartment to a nearby canyon where she knew every wildflower by its first name. Twenty minutes from home, we wallowed happily in a wonderland of color that would have done credit to an Impressionist museum in Paris.
In short, there are tourists - and travelers. Tourists wear invisible blinders and tend to regard the rest of the world as being designed, however imperfectly, for their amusement. My first and best-remembered tourists belong to a June evening in Venice. A balmy breeze, soft as the splash of our gondolier's oar, rippled the green waters of the Grand Canal; a recklessly splendid moon rose over the Lido.
We were three Americans in the boat: a middle-aged couple from Ohio and my 20 -year-old self.
Gliding under a footbridge, our stalwart oarsman burst into song. His pliant tenor soared in rapture, sobbed in despair, retreated to the most fragile of pianissimos. As it melted into the night, a flat American voice broke the silence: ''Weren't those drapes in the lobby just awful, Wilbur?''
Venice vanished. We might as well have been squashed into a crowded elevator back home.
Decades later, I stood awestruck before the Temple of the Dawn in Bangkok, dazzled by its thrusting spires. The layered magnificence of its sculpture. How much history, tradition, painstaking human labor was embedded there?
Abruptly I was elbowed aside by a squadron of visitors spilling out of a tourist bus, Nikons and Kodaks at the ready. ''Over here, Amy. Sit on the lion.'' ''Put on your funny hat, Bill.''
Only one of the crowd, a teen-age boy, seemed to see the temple as anything but photographic background. He scrutinized it carefully, then turned to me: ''How much you think all that gold is worth?''
The quintessential tourist, a subspecies prevalent in Europe in the 1950s but now virtually extinct, was the Hollywood Mogul, who traveled in packs of eight to 10 and made it a point of pride never to leave his hotel room. What could a backward foreign burg offer that had not already been created more lavishly on the back lot at Culver City?
For travelers, by contrast, I give you my neighbor Fred, who designs computer software. On a recent trip to Tokyo, Fred was invited by a Japanese colleague to visit the latter's birthplace in a remote rural village. Fred dashed for the first available train.
''Stepping across that farmhouse threshold,'' he says, ''was like stepping into the Twilight Zone. It was a dream, a fantasy out of the Arabian Nights.''
Did he feel self-conscious as the only Westerner present?
''I was too curious, too fascinated, to be thinking of myself. All I wanted to do was to merge into the setting, absorb the experience totally.''
That hungry curiosity, that urge to apprehend and comprehend, is the mark of the true traveler. I have seen Fred bring the same enthusiasm to exploring a crate of battered pottery at a California swap meet. As his wife says, ''Turn him loose on fresh terrain, and he's like a child.'' Children, of course, are the best travelers. Still imbued with the wonder of life, unburdened by inhibiting judgments, they can respond to new experience directly, spontaneously.
Somewhere along the way, many of us seem to lose that capacity. Does that mean that those who do are doomed to eternal touristhood? I doubt it. Anyone can consciously cultivate the traveler's approach. It's a matter of brushing off the barnacles of habit, hanging up one's hang-ups about alien ways, reawakening the spark of Marco Polo likely to linger in the stodgiest of souls.
It's worth a try, because in a world teetering on the fringes of Armageddon, travel offers unique rewards. It's the entry point for grasping the varied kinds of seeing and being on our shared planet, for picking up the universal patterns that lie beneath surface differences. In all climes, joy flows from familiar sources; tears spring from a common well. Travel reaches beyond tourism to illuminate the oneness of life.
It's also more fun.