Parents, repeat after me: Children are not just shorter versions of adults.

This is the important message that seems to have been missed by the geniuses at Fisher-Price, who have just announced the release this fall of the “Think Learn Smart Cycle.” The $150 toy is designed to let children age 3-6 peddle on a stationary bicycle while watching a tablet. Writing on the Digital Trends Web site, Bruce Brown explains, “Since preschoolers are drawn to technology in the form of smartphones and tablets, Fisher-Price has leveraged that fascination to help children learn and exercise. The Fisher-Price Think & Learn Smart Cycle is focused on keeping both the bodies and minds of preschoolers active.”

Now our 4-year-olds can look just like mommy on her elliptical machine at the gym, trying to distract herself with CNN while she sweats out another five minutes of interval training. What could be wrong with that?

Everything.

Starting with the “smart” part of the Smart Cycle. Fisher-Price says the apps on the built-in tablet are going to focus on science, technology, engineering and math. But there’s no evidence that more and earlier exposure to these subjects on screens is going to help our children.

Most of these apps are little more than digital flashcards. Would you sit your 4-year-old down with a math workbook? Is it somehow a better idea because the workbook makes funny sounds and lights up?

It’s not surprising, then, that despite the fact that more and more toddlers are being offered digital apps both at home and in school, there has been no improvement on academic test scores.

Indeed, the whole notion that kids need to be exposed to more academic work in preschool before they start kindergarten has been largely discredited.

As Erika Christakis, author of “The Importance of Being Little,” wrote last year about a Tennessee study: While kids who “attended preschool initially exhibited more ‘school readiness’ skills when they entered kindergarten than did their non-preschool-attending peers, by the time they were in first grade their attitudes toward school were deteriorating. And by second grade they performed worse on tests measuring literacy, language, and math skills.”

But the problem with the Smart Cycle goes far beyond the ways its creators claim to exercise a child’s brain.

There’s nothing wrong with trying to get kids off the couch even when they are using a device. Cartoons have long encouraged kids to jump around. And a little Wii tennis or dancing can be fun. But if your goal is to make a child enjoy physical activity and want to do it more, why would you want to put him on a bicycle that goes nowhere?

Not every child is going to be into organized sports and one needn’t pressure a young child to take up soccer or ballet, but exposing children to all kinds of different activities makes it more likely they’ll find one or two they like.

They won’t come to think of exercise as a chore but as something that makes them feel happy and satisfied. Many of these physical activities will also provide them with important practice at social interactions — rooting for teammates, winning with humility, losing with grace, etc. Something they’re unlikely to find with this toy unless Fisher-Price is going to offer toddler spinning classes, too.

Ages 3 to 6 are exactly when a child most needs to be exploring the people and the world around him or her. Whether it’s stacking blocks to see when they’ll tumble over, playing with paint or glue or going outside to observe plants and animals or the clouds and the stars, children at this age have the opportunity and the ability to take it all in, perhaps in ways that adults are trained not to.

In his 1890 work, “The Principles of Psychology,” William James spoke of “voluntary” and “involuntary attention.” The former, he wrote, occurs in school settings. “Voluntary attention, in short, is only a momentary affair. The process, whatever it is, exhausts itself in the single act.” But involuntary attention — or passive attention, as it has become more commonly known — involves a kind of fascination with the world at large.

James notes that “sensitiveness to immediately exciting sensorial stimuli characterizes the attention of childhood and youth.” While teachers and parents must eventually help children develop the habits of voluntary attention, it is all of these stimuli from the world around them that make them want to learn more, want to do more.

If most adults (from my small sample size) use their stationary bikes as hangers for dirty clothes, imagine how little the Smart Cycle will do to inspire children.

Naomi Schaefer Riley is a senior fellow at the Independent Women’s Forum.