“We can talk all we want about being brand-proof,” Walker writes, “but our behavior tells a different story.” Experimental subjects presented with two identical glasses of Coca-Cola, one labeled as such and the other presented as a mystery rival brand, routinely picked the one they thought was Coke as the better-tasting soda. Citing one cunningly designed study after another, Walker presents ample proof that we are only kidding ourselves if we believe we’re impervious to the multibillion-dollar marketing industry. Nevertheless, we are not “obsessed” with consumption, as many critics claim. As Walker sees it, Americans prefer not to ruminate on that particular subject, even as we shop and spend our little hearts out. “To qualify as obsessed we’d have to really think about why we buy what we buy,” Walker writes, instead of just telling ourselves that we, unlike the rest of the sheep, purchase things for purely rational, utilitarian reasons like price, quality and convenience.

If we thought about it, maybe we’d also realize that our relationship to brands and marketing campaigns has been undergoing a transformation. Marketers like to talk about the skepticism of the “new consumer,” a smart young character fleeing the mainstream and adamantly resistant to all forms of advertising. Walker begs to differ. “The only problem with this theory was that it did not match up particularly well with the realities of the marketplace that I was writing about every week in the Times Magazine,” he writes. Instead of being more hostile to what he calls “commercial persuasion,” the consumers he observed seem very much involved with brands and products. If traditional advertising has become a less effective way of fostering that involvement, the commercial persuasion industry has in turn been fiendishly resourceful in coming up with alternative methods, infiltrating hitherto unexploited aspects of our lives. The result, as Walker sees it, is a culture in which there is a “secret dialogue between what we buy and who we are,” a dialogue that shapes us even as we pretend to be untouched by it.

“Buying In” is an often startling tour of this new cultural terrain, taking in such iconic products as Hello Kitty, Timberland, Pabst Blue Ribbon and Red Bull, as well as Scion, a line of Toyotas that I, apparently, am too uncool to have known about before. Some of these brands, like Timberland and Pabst (or PBR, as the hipsters call it), were established, if small-time, entities before certain consumer subcultures adopted them. The hip-hop world took a liking to a line of boots that had been created for construction workers by a New England family company. Bike messengers in the Pacific Northwest made a Milwaukee beer the brew of choice in the indie-rock scene. In both cases, the manufacturers of those products were disconcerted by their new customers. What they understood to be the cultural meaning of their products — footwear for working men, and cheap suds for the 45-to-65-year-old Midwestern set — had been redefined by complete strangers.

This, Walker observes dryly, is what marketing managers mean when they talk of the need to “collaborate” with consumers. The CEO of Timberland became briefly notorious in hip-hop circles for seeming not to welcome the change in his customer base. (They’ve since patched things up and you can now buy pink versions of the classic work boots.) PBR was more sure-footed: The brewer carefully cultivated its image among the indie crowd by taking great care not to cultivate its image: no ads on local radio, no celebrity endorsements (despite nibbles from Kid Rock) and certainly no TV. PBR’s divisional marketing manager, cribbing tactics from Naomi Klein’s anti-corporate manifesto, “No Logo” (full of “many good marketing ideas,” he told Walker!), worked to make PBR “always look and act the underdog.” He was so successful at retaining the brand’s cachet (or anti-cachet) that one 28-year-old Oregonian whom Walker interviewed had a foot-square Pabst logo tattooed onto his back. “Pabst is part of my subculture,” the kid told the writer, pointing to the absence of Pabst advertising as evidence that “they’re not insulting you.”

Red Bull, on the other hand, set out to woo this sort of “collaboration” from the very beginning, and thus “became perhaps the quintessential example of how brands become established in the early 21st century.” The energy drink (then a relatively new product category) was launched in the U.S. nearly 10 years ago, with “no announcement or even explanation as to what this new stuff was and who was supposed to drink it and why; there was no Big Bang.” Instead, the manufacturer sprung for a variety of small events: break-dancing contests, extreme-sports tournaments, computer-gaming competitions, an electronic music workshop and free-sample distribution at gyms and nightclubs. Sponsoring so many of these efforts required what Walker refers to as “real money,” yet any given function never came across as glitzy or corporate. “The perception that these events don’t cost much to produce is good for us,” a Red Bull executive told Walker. “We don’t want to be seen as having lots of money to spend.” Walker attended a kite-boarding exhibition in Miami (enthusiasts of this new, wind-boarding-like sport were aiming to ride from Key West to Cuba) and found that it looked (very intentionally) like a nonevent: no press releases, no onlookers, no news crews, no free samples. (A videotaped press release about the stunt did get picked up on by 40 local TV stations after the fact.)

Walker calls such tactics “murketing.” In contrast to established advertising practices, which strive to communicate one, unified “Big Idea” with as much fanfare as possible, Red Bull’s campaign seemed a collection “oddly unfocused and inconsistent” efforts that “never sent a clear message to the masses.” And that turns out to be a very clever thing, since Walker has identified “projectability” as the key trait of successful new brands. Instead of telling consumers what the product is all about, the marketers invite many separate slivers of the public to define it for themselves, much as the hip-hop crowd did with Timberland boots. Red Bull “is” an extreme-sports beverage, a bar mixer, a midday pick-me-up, a workout booster, depending on whom you ask. “At worst,” Walker observes, “each group simply thinks Red Bull is something for them, partly because they have never been told otherwise.”

Younger consumers — those often referred to as Generation Y and characterized by Walker as “the least rebellious generation since the youth concept was invented” — have actually embraced the language of brands, so much so that some of them have begun inventing their own. “Streetwear,” attitudinous apparel and accessories vaguely descended from the skateboarding culture of 1970s Southern California, is their preferred medium. One of Walker’s subjects is a “professional Cool Guy” occasionally consulted on youth culture by corporations and determined to “turn my lifestyle into a business.” He concocted a brand called aNYthing (“the only brand that matters”), whose accouterments included T-shirts and caps.

Walker regards such projects as a logical progression from youth cultures past; style has always been an important way of signaling both “individuality” and membership in a particular group. True, skater culture revolved around skateboarding and punk culture around music, but each eventually reached the point where Ramones T-shirts outsold Ramones albums and the demand for skaterly “soft goods” dwarfed the demand for skateboards and helmets. Why not just skip the preliminaries and jump straight to the stuff? “In this instance,” Walker writes of the new streetwear product lines, “the symbols, products, and brands aren’t an adjunct to the subculture — they are the subculture.”

If this strikes you as absurd, even contemptible, you’re surely not alone. Even Walker, who generally gives these kids the benefit of the doubt, finds himself wondering of one “lifestyle” brand, “what, exactly, did the culture or lifestyle actually consist of — aside from buying products that represent it?” Nevertheless the purveyors see themselves as “rebellious”; they’re just communicating their defiance using “the grammar and syntax of commercial persuasion.” And, Walker concedes, this is the language that “everyone has, for better or worse, learned to speak.” Another young brand-maker he interviewed, the founder of an outfit called Barking Irons, which sells products vaguely connected to the “forgotten” history of New York City, considers his enterprise “a revolution against branding” — by which he means not the rejection of commercial expression but “the elevation of commercial expression.” Instead of big-time corporate logos with nothing to say, he offers boutique designs with a message.

This only makes sense if you argue, as Walker does, that commodities can have real significance. Some objects — trophies, wedding rings, souvenirs from trips — patently do stand for important aspects of our lives. (They have what Walker calls “authentic” meaning.) Most people, however, don’t want to admit that they believe meaning can also be bought, that Converse sneakers make you a cool outsider or that a MacBook demonstrates one’s creativity and unconventionality. Walker thinks we should acknowledge that the things we buy do carry meaning, as long as we also recognize that we’re the ones who gave it to them. A wedding ring, for example, only represents the relationship between two people because those two people (along with the society around them) agree that it does. We are the ones who invest these objects with symbolic power, and, furthermore, to do so is a universal human activity. Kidding ourselves that we relate to the objects and products in our lives in a purely rational way (something scientists have disproved over and over again) leaves us open to unconscious manipulation by advertisers.

Sam Gosling, a psychology professor at the University of Texas at Austin, also finds people’s possessions revealing. His specialty is going into rooms and offices and drawing conclusions about the people who inhabit them based on their stuff alone. While “Buying In” nimbly walks the line between consumer enlightenment and marketing advice, Gosling’s book, “Snoop: What Your Stuff Says About You,” presents itself as a helpful guide for honing largely uncalled-for skills. In the book’s main experiment, Gosling’s grad students conducted a careful study of strangers’ dorm rooms to see what they could glean from the contents. The findings are often unimpressive, such as the revelation that women’s rooms tend to contain “stuffed animals, candles and flowers” while men’s feature more CDs and “substantial stereo equipment,” along with “bills, visible laundry baskets and athletic equipment.” Besides being obvious to practically everyone, this interpretation would only come in handy if you happened to be investigating the bedroom of someone you’ve never even met — in which case, you don’t need tips on personality assessment, you need lessons in elementary ethics.

Part of the problem with “Snoop” is that Gosling’s adherence to academically quantifiable results makes for fairly broad and therefore uninteresting definitions of personality traits. Gosling uses a standard called “the Big Five,” which assesses an individual’s levels of openness, conscientiousness, extraversion, agreeableness and neuroticism. Some of his observations are piquant — people who hang posters with inspirational mottos in their offices, for instance, are probably “neurotic” (that is, anxious) rather than upbeat; the posters are meant to reassure and encourage them despite their fears. You can see past superficial attempts to appear organized (like tidiness) by looking for harder-to-fake “behavioral residue” like unalphabetized bookshelves, neglected filing systems or messes stashed just out of sight. Still, most of this book’s insights — people with lots of family photos in their office value relationships, personal Web sites are full of information about the people who maintain them, etc. — are self-evident.

“Snoop” could do with more demonstrations of Gosling’s remarkable powers (if he indeed has them) and a lot less advice. His skill, such as it is, is more of a parlor trick than a practical tool. About the only occasion in which I can imagine needing to deduce someone’s basic character by looking at their home is on a date. And if you can’t figure out whether someone is extraverted or neurotic, agreeable or cranky, by the time he invites you back to his apartment and leaves you at leisure to poke around, I suspect that either you’re incorrigibly inept at judging personality or you’re so drunk you don’t care.

On one point, both Walker and Gosling concur: When we speak the language of stuff, our primary audience is ourselves, not the proverbial Joneses we’re supposedly trying to keep up with. Gosling notes that while we sometimes attempt to “doctor” our spaces to give a better impression, this impulse is always at war with a countervailing desire “to be seen as we see ourselves, regardless of whether those self-views are positive or negative.” For his part, Walker holds up the example of Method dish soap, one of a line of cleaning products that comes in “sensational”-looking bottles and costs more than the average, ugly container of Joy. The people who buy Method, oddly enough, don’t seem to care much about the quality of the soap itself, yet they can hardly be accused of showing off their trendiness, either. “The only thing less plausible than paying a premium for high-design dish liquid simply because you want to clean dishes,” Walker writes, “is to do so because you think that any more than a tiny handful of people will ever see, notice and be impressed by the bottle.” The people who buy Method like the way it looks (or, in my case, the way it smells), but whatever statement the product makes about their taste or affluence is mainly intended for the purchasers themselves.

We go wrong, Walker believes, not when we express ourselves through our possessions, but when we allow our possessions to take precedence. It’s all too easy for people, under the influence of the siren songs of marketing (or murketing), to drift into a situation in which they use commodities “not to reflect who they are, but to construct who they are. Not to reflect a self, but to build a self.” No object, of course, is meaningful enough to fulfill that role, and an endless cycle of chasing after glittering but ultimately unsatisfying products is likely to ensue. Pretending that the stuff in our life is simply, mutely functional might seem like an antidote to this cycle, but in its own way, it’s just as delusional.

Your stuff is always talking about you, behind your back and to your face. To find out whether it’s telling the truth, you have to listen.