Reasoning and judgment under uncertainty are often based on a limited number of
simplifying heuristics rather than formal logic or rule-based argumentation. Heuristics are
low-effort mental shortcuts, which save time and effort, and usually result in accurate
judgment, but they can also lead to systematic errors and biases when applied
inappropriately. In the past 40 years hundreds of papers have been published on the topic
of heuristics and biases in judgment and decision making. However, we still know
surprisingly little about the development and the cognitive underpinnings of heuristics and
biases.
The main aim of my thesis is to examine these questions. Another aim is to evaluate
the applicability of dual-process theories of reasoning to the development of reasoning.
Dual-process theories claim that there are two types of process underlying higher order
reasoning: fast, automatic, and effortless (Type 1) processes (which are usually associated
with the use of reasoning heuristics), and slow, conscious and effortful (Type 2) processes
(which are usually associated with rule-based reasoning).
This thesis presents eight experiments which investigated the development of
reasoning heuristics in three different populations: typically developing children and
adolescents between the age of 5 and 16, adolescents with autism, and university students.
Although heuristic reasoning is supposed to be basic, simple, and effortless, we have found
evidence that responses that are usually attributed to heuristic processes are positively
correlated with cognitive capacity in the case of young children (even after controlling for
the effects of age). Moreover, we have found that adolescents with autism are less
susceptible to a number of reasoning heuristics than typically developing children. Finally,
our experiments with university students provided evidence that education in statistics
increases the likelihood of the inappropriate use of a certain heuristic (the equiprobability
bias). These results offer a novel insight into the development of reasoning heuristics.
Additionally, they have interesting implications for dual-process theories of reasoning, and
they can also inform the debates about the rationality of reasoning heuristics and biases