Here's a common modern scene.

I'm at the airport, waiting to collect my luggage at the end of a trip. Around me are people doing the same. These are people who have the money and brains to manage an airplane trip for the entire family. Kansas City is a center for engineering, government and medicine, so presumably these people have education and skills.

Yet many of them allow their small children to step up to the baggage carousel and put their fingers on the moving parts.

Are they intelligent?