All processes display variation. As a consequence, decisions entail uncertainty. A standard procedure in decision analysis--the practice of and techniques for aiding decision-making--is to attempt to formally incorporate the uncertainty through a metric, typically probability. Even in more informal decision making, we deliberate risks and uncertainties in arriving at our decisions. Thus, probability assessment has arisen as a major topic in the study of decision-making.

Since the product of probability assessment (i.e. a subjective probability) is clearly a judgment, it is not very surprising that assessment usually has been described as a judgmental activity or process. Judgment, as a process, involves a weighing or scaling activity by which a stimulus is evaluated against some criterion or, in this case, along some dimension (the 0-1 probability scale). However, the process by which the output judgment is constructed is not purely or even primarily judgmental. Instead, the process is dominated by the construction of reasoned arguments.

It is this general statement that motivates and summarizes this chapter. In Section 9.2 we characterize current accounts of probability assessment as being primarily judgmental in nature. The section ends by noting how researchers have begun to implicitly acknowledge that such ap account has important limitations. Section 9.3 takes a step beyond the boundaries of a judgmental account of probability assessment; it derives a theoretical framework that encompasses reasoning and other nonjudgmental processes in a cognitive theory of probability construction. This account is applied in Section 9.4 in looking back at and reinterpreting "judgmental" phenomena that have been documented in the behavioral decision literature. Finally, Section 9.5 notes that progress consistent with the theory of this chapter is being made by researchers, and expresses the hope that this progress will continue.