ABSTRACT
Linguists and philosophers have long discussed and investigated scope ambi-
guities in natural language. Our aim in this paper is to initiate the psychological
study of scope ambiguities caused by modal operators, especially the probability operator, in conditionals (see Egre & Cozic, 2012, and Kratzer, 2012, for relevant points in philosophy and linguistics). This topic must be addressed by
any theory of natural language conditionals, and the new Bayesian and proba-
bilistic approaches to the psychology of reasoning should direct attention to
the explicit use of probabilistic, and more broadly epistemic, qualifiers in con-
ditionals. These operators, particularly probably and its cognates, are often
used explicitly in natural language to qualify conditionals. These uses illustrate
the fundamental point of the new approaches that most everyday and scientific reasoning takes place in a context of uncertainty (Oaksford & Chater, 2007,
2009). It is helpful to begin by illustrating some basic points with scope
ambiguities caused by negation in natural language (see Handley, Evans, &
Thompson, 2006, and Pfeifer, 2012, on the scope ambiguities of negation in
conditionals). Consider the quote from a number of sources including
Shakespeare’s The Merchant of Venice, where it is almost identical to:
(1) All that glitters is not gold.
