IQs have dropped for the first time in American history, and the experts aren’t quite sure why.

According to Neuroscience News, a new Northwestern University study finds that our average IQ scores have decreased in three out of four cognitive measures.

The study found that “scores of verbal reasoning (logic, vocabulary), matrix reasoning (visual problem solving, analogies) and letter and number series (computational/mathematical) dropped during the study period...”

The only IQ measure to increase was 3D rotation (spatial reasoning), which, ironically, could be due to the proliferation of video gaming.

The country’s IQ drop is a drastic reversal of the “Flynn effect,” a phenomenon in which “IQ scores have substantially increased from 1932 through the 20th century, with differences ranging from three to five IQ points per decade.”

Elizabeth Dworak, the study’s author, says the findings do not mean Americans are necessarily getting less intelligent.

“It could just be that they’re getting worse at taking tests or specifically worse at taking these kinds of tests,” she says.

Perhaps.

Or perhaps our outdated and dumbed-down approach to learning and teaching are making us duller.

When my parents graduated high school in the 1950s, they were well prepared to read, write clear and coherent letters (what we call “content” today), do basic math and manage their checkbooks.

That was a different era, to be sure.

But here we are, more than 60 years later, still running our kids through a creaky education model that seems more interested in promoting peripheral cultural shifts than in teaching the rigors of reading, writing and arithmetic.

Is it any wonder that the cognitive skills of American kids fall well below kids in 25 other developed countries, according to The Discovery Institute?

Meanwhile, as our kids spend eight hours a day on social media, their attention spans and ability to concentrate are being compromised, The Guardian reports, to no one’s surprise.

How can they ever learn to read and understand long essays or make a detailed, reasoned argument if they cannot focus and concentrate on anything more complicated than a text message?

Another key driver of the country’s declining cognitive abilities could be that our Digital Age kids no longer spend hours outside playing.

Richard Louv, author of “Last Child in the Woods,” says our kids are suffering from “nature deficit disorder,” which he argues is a direct cause of attention deficit hyperactivity disorder (ADHD) and other learning maladies in children.

Simply put, our kids spend too little time climbing trees, building forts and having all five of their senses engaged and unleashed by the wonders of playing in the woods.

“We don’t yet know why it happens,” says Louv, “but when all five of a child’s senses come alive, a child is at an optimum state of learning. Creativity and cognitive functioning go way up.”

And conversely, as our kids spend more time indoors on social media, their creativity and cognitive functioning go way down.

All of this IQ decline is putting our country at a crossroads.

As our Digital Kids become adults, their votes are increasingly replacing those cast by the common-sense high-school grads of the 1950s.

To maintain a stable and prosperous republic, and to thwart the silver-tongued politicians who push their expensive and foolish government policies, we will need voters with sound reasoning abilities.

That’s one more good reason why we must reform our education system — and moderate the impact of social media on our kids — to re-reverse the Flynn effect while we still can.

Purcell, creator of the infotainment site ThurbersTail.com, which features pet advice he’s learning from his beloved Labrador, Thurber, is a Pittsburgh Tribune-Review humor columnist. Email him at Tom@TomPurcell.com