Thinking and Deciding

20 WHAT IS THINKING?
not move. (Why should it?) The second would become vertical. Perhaps this naive
theory results from reliance on a false analogy with a balance.
Another of McCloskey’s studies involved asking subjects to trace the path of
a ball after it rolls off the edge of a table. One incorrect answer is shown in the
following illustration, along with the correct answer. Subjects seem to think that
the impetus from the original force takes a little time to dissipate, but that once
it does, gravity takes over and the ball falls straight down (much like movie cartoon
characters, who usually look first, then fall). In fact, the momentum from the original
push keeps the ball moving at the same speed in the horizontal direction, and the path
changes direction only because the downward speed increases.
McCloskey (pp. 321–322) argues that these naive theories are not entirely harmless
in the real world:
An acquaintance of ours was recently stepping onto a ladder from a roof
20 feet above the ground. Unfortunately, the ladder slipped out from
under him. As he began to fall, he pushed himself out from the edge of
the roof in an attempt to land in a bush about 3 feet out from the base
of the house .... However, he overshot the bush, landing about 12 feet
from the base of the house and breaking his arm. Was this just a random
miscalculation, or did our acquaintance push off too hard because of a
naive belief that he would move outward for a short time and then fall
straight down?