Illusions in Reasoning About Consistency
P. N. Johnson-Laird,
1*
Paolo Legrenzi,
2
Vittorio Girotto,
34
Maria S. Legrenzi
5
Reasoners succumb to predictable illusions in evaluating whether
sets of assertions are consistent. We report two studies of this
computationally intractable task of "satisfiability." The results
show that as the number of possibilities compatible with the assertions
increases, the difficulty of the task increases, and that reasoners
represent what is true according to assertions, not what is false. This
procedure avoids overloading memory, but it yields illusions of
consistency and of inconsistency. These illusions modify our picture of
human rationality.
1 Department of Psychology, Princeton
University, Princeton, NJ 08544, USA.
2 Department
of Philosophy, Milan University, 20122 Milan, Italy.
3 LPC CNRS, University of Provence,
Aix-en-Provence 13100, France.
4 Department of
Psychology, University of Trieste, 34100 Trieste, Italy.
5 Department of Psychology, Padua University, 35100 Padua, Italy.
*
To whom correspondence should be addressed. E-mail:
phil{at}princeton.edu
