WHY DO the seats get smaller as the airplanes get larger?
Why does voice mail seem to double the time to complete a telephone call?
Why has the leisure society gone the way of the leisure suit?
The world seems to be getting even with humankind, twisting our cleverness against us. Or we may be unconsciously twisting it ourselves.
This is not a new phenomenon, but technology has magnified it.
Whenever we look we face unintended consequences of mechanical, chemical, medical, social and financial ingenuity.
They are revenge effects and they are less the malignant ironies of a spiteful world than the results of a lack of human foresight.
They fall into major categories:
Repeating occurs when a task is made easier or faster but becomes required more often.
In the 1980s companies spent billions of dollars on personal computers, yet in 1989 the services sector showed its smallest productivity growth of the postwar era.
For example, when making a spreadsheet was laborious, people did it as seldom and as cautiously as possible. Computers have simplified them, but bosses demand them more often.
Recomplicating is another consequence of computer simplification.
Touch-tone telephone were introduced to increase dialing speed, but now the time saved by punching has been consumed by systems built to take advantage of it.
Combining the telephone number, the carrier access code and credit card number, a call may require 30 digits -- more if a voice-mail machine answers.
In recongesting, an updated function becomes slower and less comfortable than the original.
Technological change opens new frontiers only to clog them up again.
Planners dreamed of the automobile-based suburb as an antidote to the crowding of cities and the power of railroads and urban landlords.
But rapid traffic flow has turned out to be unrealistic, as cars inch down roads bumper to bumper.
The historian and philosopher Ivan Illich has estimated that the average American now spends 1,600 hours driving or working to support transportation costs "to cover a year's total of 6,000 miles, four miles per hour." He says, "This is just as fast as a pedestrian and slower than a bicycle."
Finally, rearranging is the revenge effect that delays a problem or moves it physically, usually magnifying its effect.
The geologist W. Barclay Kamb, in John McPhee's "The Control of Nature," described efforts to channel the flow of debris from the San Gabriel Mountains in California: "You're not changing the source of the sediment. Those cribworks are less strong than nature's own constructs . . . . Sooner or later a flood will wipe out those small dams and scatter the debris. Everything you store might come out in one event."
Likewise, suppressing forest fires builds up combustible materials for even larger conflagrations. And disaster control and relief risk increasing casualties by encouraging occupation of unsafe areas.
The existence of revenge effects should not end the pursuit of convenience and increased productivity.
We should bear in mind that change never offers complete solutions and be prepared to deal with its negative consequences.
Innovation involves not only imperfect machines but also unpredictable people.
Revenge effects don't mean that progress is impossible, only that in planning for it we must look more to Rube Goldberg than to Isaac Newton.
Edward Tenner is executive editor at Princeton University Press.