Thinking and Deciding

KNOWLEDGE, THINKING, AND UNDERSTANDING 21
Naive theories may also have some advantages. Kempton (1986) found that people
tend to hold two different theories of home heat control. The physically correct
theory for the vast majority of homes in the United States is the feedback theory. By
this theory, the thermostat simply turns the heat on and off, depending on the temperature.
As one Michigan farmer put it, “You just turn the thermostat up, and once
she gets up there [to the desired temperature] she’ll kick off automatically. And then
she’ll kick on and off to keep it at that temperature.” By this theory, it does no good
to turn the thermostat way up to warm up the home quickly. People who hold this
feedback theory leave the thermostat set at a fixed value during the day.
Many people hold a different view, the valve theory. By this view, the thermostat
is like the gas pedal of a car. The higher you turn it up, the more heat goes into the
house, and the faster the temperature changes. People who hold this theory turn the
thermostat way up when they come into a cold house, and then, if they remember,
turn it down after the house warms up. The valve theory may well lead to wasted
fuel, but it does give people a simple reason why they ought to turn the thermostat
down when they are out of the house: less fuel will be used when the setting is lower.
The feedback theory is technically correct, as can be ascertained by looking inside
a thermostat; however, it has some serious drawbacks. First, the valve theory
does a better job than the basic feedback theory of explaining certain phenomena. In
many homes, thermostats do need to be set higher to maintain the same feeling of
warmth when it is very cold outside. This is easily explained by the valve theory, but
in the feedback theory other concepts must be invoked, such as the fact that some
rooms are less well heated than others and that some of the feeling of warmth may
come from radiant heat from the walls and ceiling. Likewise, it may be necessary to
turn the thermostat up higher than normal when entering a cold room, because the
walls and furniture take longer to come to the desired temperature than the air does,
and the room will still feel cold even after the air (which affects the thermostat) has
reached the desired temperature.
Second, the feedback theory does not easily explain why it is a good idea to turn
the heat down when one is out of the house. One valve theorist felt that the heat
should be turned down when one is out, but, she said, “My husband disagrees with
me. He ...feels, and he will argue with me long enough, that we do not save any
fuelbyturningthethermostatupanddown.... Because he, he feels that by the time
you turn it down to 55 [degrees], and in order to get all the objects in the house back
up to 65, you’re going to use more fuel than if you would have left it at 65 and it just
kicks in now and then.” Now the husband’s reasoning here is physically incorrect.
The use of fuel is directly proportionate to the flow of heat out of the house, and
this, in turn, depends only on the temperature difference between the inside of the
house and the outside. Thus, the house loses less heat, and uses less fuel, when it is
at 55 degrees Fahrenheit than when it is at 65 degrees; but, as Kempton notes, the
physically correct argument requires a more abstract understanding than most people
typically achieve. If they act according to the valve theory, they may actually save
more energy than if they act in terms of a rudimentary feedback theory, such as that
held by the husband in this example.