Today, we try to get rid of the instruction manual. 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.

My favorite cafe has a door handle in the shape of a flat plate. The sign above it says PULL. Visit after visit I push the door instead of pulling on it. I thought I might be brain-damaged. Now I've read Donald Norman's book, Turn Signals Are the Facial Expressions of Automobiles, and I am vindicated.

That flat plate is a clear invitation to push. The question is, are you tuned to visual cues or verbal ones? You have to be tuned to the written word to notice the word PULL before you react to the plate. If you're better tuned to mechanical function, and most of us are, you'll see that inviting plate first.

Next Norman goes to a scene I was in last summer. Sydney, Australia, takes great pride in its downtown monorail system. When I tried to use that system, it gave me fits.

It's all well labeled. Yet they need an attendant to help people like me through the gate. Norman looks at that system for visual cues. You look for a place to put your token. But the first slot you see on the gate is the one where your ticket comes out. "We've tried all sorts of signs," the attendant complains. "People just can't seem to read."

It gets worse: The command on the left side of the token dispenser tells you to push a button on the right. The command on the right tells you to put a coin in the slot on the left. The visual and written cues contradict each other.

I remember rushing to my meeting, trying to get a token in a hurry and having to go to the attendant for help. The system is, indeed, a masterpiece of misdirection.

Norman moves on. He shows us electric stoves where the switches don't match the burners. A low ice-cream freezer cabinet, at the end of a lunch line, has sliding doors on top. You obviously lay your tray on one side while you open the other.

Trouble is, the glass doors aren't meant to support any load. The top is cracked, of course. Too late, they've pasted a sign on it: "Please do not put your tray here."

So I add my own examples. A friend hands me a key and asks me to lock his car door. "I already did." "But I have the key," he says. By pure accident I'd read the manual for a similar car. I knew how to lock it without the key by moving the handle. But who reads manuals? Normally I don't. After 50,000 miles of use, he still didn't know. There was no visual cue.

Instructions are such clumsy things. Machines can so easily be self-explanatory. A good machine leads the eye accurately. But designers can forget how much information still flows when nothing at all is written -- when nothing is said.

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

(Theme music)

Norman, D.A., Turn Signals Are the Facial Expressions of Automobiles. New York: Addison-Wesley Publishing Co., 1992.