IT'S NOT AS easy as it sounds.

Late one summer afternoon in New York's Greenwich Village, I strolled into a neighborhood delicatessen to find a group of locals carrying on a "blind" tasting of soft drinks. Taster after blindfolded taster failed to recognize the difference not only between the two biggies, Coke and Pepsi, but even between the colas and the noncolas. Some Villagers guessed some sodas right, but almost nobody guessed them all, and a fair number of tasters confused such unlikely beverages as ginger ale and Royal Crown Cola, 7-Up and Coke. Certainly I would never confuse Coke and Pepsi, I thought smugly, and most of the people I told the story concurred.

But Pepsi knew what it was doing when it issued its "Pepsi challenge" in Dallas, doubled its market share there, then took its show on the road. In store after store, Pepsi set up booths where shoppers could sip two similar-looking glasses of cola (Pepsi and Coke) and register their preferences. Fifty-two percent of the millions who took the test preferred the Pepsi, 42 percent preferred the Coca Cola, and 6 percent didn't care one way or the other, according to a recent industry report.

Miffed that nobody had invited me to a Pepsi challenge, and uncertain that a soft drink company was the most objective sponsor of a soft drink tasting, I recently held a series of my own tastings.

The first preceded a dinner party for which the guests had bid $35 a couple in an auction; people like that, it seemed, would pay more than the usual attention to what they put in their mouths. The 11 who took part in the tasting knew they were tasting Coke and Pepsi, but didn't know which of two identical dark glasses contained which soda, and didn't watch any of the other tasters before their turn came.

With this small a sample, you can't generalize from the fact that five people preferred the Coke, five preferred the Pepsi and one liked neither. What is interesting is that some people thought the Coke was sweeter and some the Pepsi. One taster said that the Coke had a sharper, more complex taste, in contrast with Pepsi's single, predominant, but slightly metallic taste (both sodas were bottled, not canned). Another taster said that Coke was a combination of two tastes that didn't blend very well -- and that the Pepsi "blended together at a higher level."

Most of the guests could figure out that Coke was Coke and Pepsi Pepsi, but not easily -- they took a long time deciding, and so did I. We were all surprised at our own uncertainty.

The idea of the Pepsi Challenge was to see which of two colas people preferred. What struck me was that they couldn't tell what they were drinking even if they had expressed a strong preference beforehand. This seemed to be especially true with children, who traditionally hold strong prejudices about food and drink, even (perhaps particularly) those they have never tried.

For the next tasting, I asked 40 fifth- and sixth-graders to submit to a blindfolded tasting of four sodas: Coke, Pepsi, Royal Crown and 7-Up. Recognizing the social studies possibilities in a blind tasting of heavily advertised products, their teachers asked the students to write an essay beforehand on why they preferred Coke or Pepsi over its main competitor. Opinions ran strong, with 24 favoring Coke, 14 Pepsi and two abstaining. Fourteen kids thought Coke was the sweeter of the two soft drinks; only four thought Pepsi was, although four other students complained that Pepsi was too sweet and only three complained that Coke was. (In fact, Pepsi contains 5 percent more sugar than Coke.) Eight essayists thought Coke tasted fizzier than Pepsi, three thought it stayed cold longer, 10 wrote that it had more flavor and seven claimed that Coke tastes better with food, particularly pizza, picnics and cookouts--a reflection, it seemed, of effective "things go better with Coke" ads. Seven Coke fans said Pepsi had a bad aftertaste, four found Pepsi watery, and three, flat.

By and large, the Pepsi fans thought Coke was too strong-tasting, and found Pepsi "smoother." To some, Pepsi was tangier and had more flavor, had more bubbles, but was less "gassy." Coke, according to one student, "makes my teeth squeak;" another opined that "Pepsi doesn't get my teeth soft."

So much for preconceptions.

I told the children beforehand that two of the soft drinks were Coke and Pepsi, and that I wanted them to guess from past experience what the other two were. Because 7-Up was one of the drinks tested, we blindfolded the tasters. All of the sodas were from bottles, all were equally cold, and they drank them from numbered paper cups, with no ice. (In my view, ice changes the level of carbonation, differently in different sodas.)

In terms of product identification, 7-Up came out most recognizable of the four sodas tested: although I hadn't mentioned it by name, 22 of the 40 children identified it correctly, and only 12 thought it was Sprite, another soda in the lemon-lime category. Of the colas, Pepsi scored highest, with 23 correct identifications out of a possible 41. Only 16 students out of 41 pegged Coke as Coke, and only 14 students guessed Royal Crown. When you consider that Coke is one of those brand names (like Kleenex and Xerox) so basic that it's become something of a generic term, it's amazing that Coke would be only fractionally more recognizable than Royal Crown, a product whose name I hadn't mentioned to the children and whose image on the soda pop scene is relatively modest.

Only 12 children identified both Coke and Pepsi correctly; only 6 got all three colas right; only four guessed all four sodas (and "guess" is probably as good a word as any for this mini-set of statistics).

In a similar identification test, adults fared no better than the children did, although we made the mistake of including too many sodas in the adults' informal and somewhat chaotic tasting of Coke, Pepsi, Sprite, 7-Up, Dr. Pepper and Royal Crown. The soda that showed the most distinct personality was Dr. Pepper, which had a smell that tasters considered clearly distinguishable from the others. Coke was confused with two other colas and 7-Up. Pepsi also was identified as two other colas. Sprite was tagged as Sprite, 7-Up, Coke and "a white one." Seven-Up was still the "uncola," being mistaken only for Sprite, Mountain Dew and ginger ale. Only one person identified RC as RC -- this older generation, which has obviously experienced less of it than the schoolchildren, thought it was anything from Coke to ginger ale.

With few exceptions, the participants in these soda tastings were amazed at how little their preferences seemed to be based on taste. Soft drink companies seem well aware of the phenomenon, focusing their advertising far more on the image of an active life style than on the taste, and particularly the sweetness, of the beverage.

You think you can tell the difference? Get out your blindfolds!