Introduction

This paper contains an introduction to some of the results and observations we have accumulated from a series of studies on the task of assessing the probative value of inconclusive or probabilistic trial evidence. Some of these studies are formal or logical in nature and concern the manner in which the probative value of evidence should be assessed coherently. The other studies are empirical and behavioral in nature and concern the manner in which persons actually do assess the probative value of evidence. Our dual concern was voiced by Wigmore (1937, p. 8), who expressed interest in “…the reasons why a total mass of evidence does or should persuade us to a given conclusion, and why our conclusions would or should have been different or identical if some part of that total mass of evidence had been different.” Our formal and empirical studies have proceeded hand-inhand. Formal research helps to identify meaningful variables and measures for empirical research; empirical research, interesting in its own right, is also useful in testing the adequacy of the foundations for formal studies.

A major focus of our research has been upon inductive inference tasks, which Wigmore termed “catenated‘rdquo;; the modern terms for these tasks are “cascaded” or “hierarchical” (Wigmore, 1937, p. 13). Wigmore was the first to point out the fact that most inferential reasoning tasks are cascaded in nature. A cascaded inference task is composed of one or more reasoning stages interposed between evidence observable to the factfmder and the ultimate facts-in-issue.