No. 247:
Piaget and Mechanism

Today, we ask children to explain bicycles. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

The psychologist Jean Piaget asked young children how a bicycle works. Their answers help us see how our machines teach us. He begins with four-year-olds. They see the bicycle as a whole -- a thing that goes entirely of itself. We listen as a psychologist questions a child:

How does this bicycle go?

With wheels.

And how do the wheels turn?

The bicycle makes them turn.


With the handle-bar.

How does the handle-bar make the bicycle go?

With the wheels.

And what makes the wheels turn?

The bicycle.

And so forth. Parts are called into the explanation and just as quickly dropped -- for the bike is entire unto itself.

When children are closer to six, they start referring to parts, but not in any orderly cause-and-effect way. Your hear things like:

What makes the chain turn?

The wheels.

What makes the wheels turn?

Those brake wires.

As the child approaches 8, he starts using cause-and-effect sequences that pass from one part to another. But he has trouble getting them right. The feet turn the pedals, and they drive the chain, and it turns the sprocket, which drives the wheel. But he's not sure what turning the handle-bar has to do with propelling the bike.

Only as they approach 9 can most children sketch a bike from memory and explain how the parts work. It's a lesson for all of us, surrounded as we are by so many machines we don't understand. Suppose you ask a person how his computer works. He might answer:

You turn it on.

What does it do?

It writes letters and does math.


You type on the keyboard.

What's that whirring sound?

That's its motor.

What does it do?

It helps figure out the answer.

And so forth. The machine we don't understand is a machine entire unto itself. Parts that we don't understand aren't elements in a causal chain. They're only aspects of a functioning whole.

Piaget's children and their bicycles tell us how we ourselves come to understand things. It's a peculiarity of Western thinking that we analytically decompose things into cause-and-effect sequences. What Piaget doesn't tell us is that, at the last, we have to put the parts back together. We have to reclaim the child's view.

The truest answer to the question, "How does the bicycle work?" is that you and the machine become a single thing. The wheels, chain, and sprocket are forgotten as you sail down the road with the wind blowing through your hair.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Piaget, J., The Child's Conception of Physical Causality. Totowa, NJ: Littlefield, Adams & Co. 1969, Sect. III, Explanation of Machines.


The then-new safety bicycle as represented in Appleton's Cyclopaedia of Applied Mechanics in 1892