GAME-SHOW AFICIONADOS FONDLY REMEMBER THE CONSU merist orgasm that closed every episode of “Let’s Make a Deal.” As a lovely hostess seductively stroked the merchandise, prize after prize was paraded before the lucky winner, starting with “Rice-A-Roni, the San Francisco Treat,” and invariably climaxing with “ your … new … CAR!!!! ”

In the 1970s the next-to-last item in this barrage was often a top-of-the-line Wurlitzer electric piano with built-in percussion. At the flip of a switch it could provide canned rhythms ranging from rock (“tsss-chicka, tsss-chicka, tsss-chicka”) to boogie-woogie (“bum bum bum bum BUM bum burn bum”) and so on through waltz, disco, bossa nova, and assorted other genres. Never again would you need to hire a drummer for your family room or den! The studio audience reacted with awe.

Such amazement seems unfathomable today, when you’ll find more sophisticated electronics sold from blankets on the sidewalk. In fact, even as Carol Merrill was trailing her manicured fingers over the keyboard, advances in microelectronics were making the bulky showpiece obsolete. By the early 1980s a few hundred dollars would buy any aspiring Flock of Seagulls imitator the popular Casio CT-IOl, or one of many other portable keyboards whose versatility put the mighty Wurlitzer to shame.

The drum machines that came with these keyboards could supposedly be programmed by the user, but the required degree of skill would have been way beyond the average musician of the era even without drugs. So most of them stuck to the pre-set rhythms. These were undeniably convenient: They never sped up or slowed down—never changed at all, in fact—and if you didn’t get any Keith Moon-type fills, you wouldn’t get any Keith Moon-type behavior either. A generation of bands spent their formative years setting up a cheesy groove, laying down a synthesizer track, and then running off to get their hair done. And that’s why 1980s dance pop was so lame.

This sorry tale illustrates a common pattern in the history of technology: A new process or device replaces an old one, letting users do 95 percent as good a job with only 5 percent of the work. In principle, the final 5 percent of the job can be duplicated; in practice, it gets ignored.

Examples of this are virtually numberless; most readers will already have thought of their own. But to become accepted as a serious analytical tool, it needs a snappy name. When professors discuss technological history, they toss around terms like revenge theory (nothing ever turns out the way you meant it to), reverse salient (bottleneck), and progress talk (the notion that things are getting better). For our concept, we considered such mouthfuls as the 5-95 rule and marginal truncation , until a fortuitous late-night radio encounter with Soft Cell yielded an ideal moniker: The Casio Effect.

The Casio Effect shows up all over. Computerized spell checker, for example, is a wonderful technology. It catches almost as many typos as a human proofreader and doesn’t put question marks next to all your jokes. You can go over the manuscript yourself to catch the typos it missed, though that would defeat the purpose of a laborsaving device.

The phenomenon is not restricted to information technology, or to the recent past. In the 188Os the Kodak camera made photography accessible to the masses—at the price of imposing a certain sameness on the results. Half a century later frozen food greatly reduced kitchen drudgery —with an accompanying cost in flavor. But computers seem especially prone to the Casio Effect, such as when the ease of Internet research makes students reluctant to look any- thing up in a book.

In most cases the benefits of the reduction in workload far outweigh the loss in quality. It’s important to know, however, when almost is not enough. The Casio Effect caused enormous controversy in the 2000 presidential election, when some politicians asserted that the rapid mechanical tally differed from what a hand count would have shown. Automatic pilots have gotten very sophisticated, but few of us would fly in a plane without a human at the controls. And a too-heavy reliance on computerized calculations and projections has led to numerous building collapses and other disasters through the years. Such cases serve as a reminder that when overlooked, the Casio Effect can have results that are a lot more serious than typos, soggy green beans, or even Tears for Fears.