A kid's consumer soul in full cry is an ugly thing, not only because his repetitive, snot-choked whine can feel like a rusty, serrated blade sawing back and forth in your ear, but because we recognize that bloody howl as our very own. Indeed, one adequate definition of adulthood might be the ability to tamp down and dissemble this clamorous need for shiny, whirring purchasables. Grown-ups can rationalize: The box-set of Philly Sound CDs will boost my husband's spirits, or that tasty linen jacket will come in handy for job interviews. But, at bottom, truly, toys are us. Tikes know this and feel no shame. Their trick is to get their outsized greed in sync with your guilt about yours. When that happens, it's two more babes bound for toy land.

Was it always thus? Two new books -- "Kid's Stuff: Toys and the Changing World of American Childhood" by Gary Cross and "What Kids Buy and Why: The Psychology of Marketing to Kids" by Dan S. Acuff and Robert H. Reiher -- treat the gimme complex with high seriousness, providing both historical context and psychological insight. Cross gives us the big picture, toy-wise, how, over the past century, educational theories, child-rearing manuals, toy makers and modern marketing have shaped young consumers and what they consume. Acuff and Reiher are those modern marketers, and they've written an instruction manual on how to turn your cherub-faced li'l darling into a foaming, spitting knot of Barbie-crazed lust.

Back in the good old days, before Ninja Turtles, even before Pez dispensers, back in the 15th century, toys as such didn't exist. Wealthy children played with objects -- manger scenes, Noah's arks, engravings of animals or battles -- that originated as amusements for adults. For example, fashion dolls originated in the Middle Ages as portable mannequins on which the latest Parisian styles might circulate. After this practical service they would be passed along by mothers to daughters. Among the hoi polloi, rag-and-straw dolls or balls made out of animal wastes were popular. (They still are if you think about tossing around the ol' pigskin, originally a pig bladder.) But overall, considerable congruence existed between adult and child play and, as Cross points out, playthings "served common purposes in introducing the young to the tools, experiences and even emotional lives of their parents."

You can only have so much fun with animal waste. In the late 19th century, items like roller skates, bicycles, mechanical banks, sleds, air rifles and jack-in-the boxes made their mass-produced appearance. About this time the bacchanal excesses of Christmas were tidied up for domestic use and rechanneled as gift giving, especially to the young. Newly erupting parental anxiety about children's need for creative outlets dovetailed with this holiday ethos to launch a juggernaut of tinker toys and teddy bears. Trailing in its wake would come exhausted Santas and parents wrung free of their last dime by their child's trembling lip and the words "I wanna."

Over subsequent decades, toys evolved from reflectors of adult lives -- erector sets, doll houses, model railroads -- to embodiments of childhood fantasy. If playing with Civil War soldiers at least bore some relation to history, Flash Gordon ray guns bore less, and Power Rangers bear none at all. All three product lines share the common denominator of violence, but only the old-fashioned toy soldiers offer the possibility of a moral context. "Toymakers," Cross writes, "seem like pied pipers leading our children away from us." And even so-called educational toys (toy manufacturing czar Leo Marx once said they were purchased only by "spinster aunts and spinster uncles and hermetically sealed parents who wash their children 1,000 times a day") unavoidably promote that consumption-now-or-else mentality kids seem to inhale from us like air. But it's not really that grim, is it? Parents do get a piece of the action, what Thorstein Veblen called "vicarious consumption," and from that flows an undeniable delight. Small windfalls I once spent on myself I started using to buy German-made, zoologically accurate dinosaurs for my little boy. (After close inspection of cheaper reptile replicas, I determined there was no comparison with the imported models.) Satisfying my own consumer itch with an arguably "educational" toy that lit the boy up like he'd mainlined a couple of Milky Way bars seemed to be a good deal. But soon after beginning to bring home these occasional treats, I found myself being greeted at the door by my 3-year-old's avid inquiry, "Whatchu got for me?" And, if that wasn't heart-sinking enough, the demand soon turned imperious. I was being shaken down for Mesozoic miniatures. Delight turned sour as it turned to obligation, and I realized my toddler had come of consumer age. He and I were entering the threshold of mature relations -- we could now bargain and bicker over goods. As defensive prep for these brutal negotiations you could do no better than read Acuff and Reiher's "What Kids Buy." The book's flap copy reads, "If you're in the business of marketing or developing products and programs for kids, [this book] belongs in your office." The authors trumpet their 20 years of consulting for Nike, Tyco, Disney, Pepsi, Mattel, Hasbro, Sega and Kellogg's. So if you want to know why your child's soul is on fire for some soda, snack or gadget, these guys can tell you. They muster up scads of scientific data to put their finger on the "moral sense," "humor," "neurology" and "needs" of kids at every age. Did you know that for 3-to-7-year-olds, "the right brain, which specializes in nonlinear, nonlogical abilities, such as visuospatial acuity and music, is being emphasized developmentally"? Toy packagers are then advised to make use of "a character or glittery heart symbol ... to grab and hold this child's attention." "Visuospatial acuity" sounds to me like an old Moody Blues tune, but even I know that "glittery" stuff catches a kindergartner's eye. Yet the general obviousness of most of the marketing ploys laid out here doesn't make the book less scary; the punctiliously assembled research, complete with involved charts and diagrams, gives the unmistakable impression of plans for a military campaign: This book is the blueprint for D-Day and your children are Paris and Berlin. When describing kids motivated to ask their parents to buy something, Acuff and Reiher refer to "purchase influence" or what is commonly known in the toy biz as "the nag factor." The candor is appreciated; they're out to make your job as a parent just a teensy bit harder. But, even with their fiendish plot in your hands, what can you do besides send your kids to a Tibetan monastery? Since the incubus consumerus dwells everywhere, one smuggled Gameboy would shoot the whole place to blink 'n' beep hell. After a couple of nights of being whined and wheedled nightly for new dinosaurs, I sat my son down and patiently explained that we should enjoy each toy completely before moving on to the next, that one toy at a time was like having a best friend to have fun with and care about, that a gift was a special thing for special times, and that the best gift Mommy and Daddy could ever get was a hug and big kiss from our little guy. His eyes softened and his head inclined sympathetically toward me as I finished. "Daddy," he purred, "whatchu got for me tomorrow?"