Models of Contract Law III

Coherence based reasoning and models of contract law

In research conducted by Natalie Close under the supervision of Ted Wright and Andrew Heathcote (School of Psychology), near-graduation law students who had completed Contracts were asked to rate, at 4 stages in the decision-making process, the importance of facts assigned to 3 categories differentiated by degree of relevance, using one of two law models: Australian case law (detailed rules) and the ACC (broad principles). The MCL3 materials were based on the Models of Contract Law I materials.

An important result was the replication of the Models of Contract Law I materials data on consensus among decision-makers who were more fully-trained. Decision-makers using the ACC agreed with each other significantly more often than users of the common law, especially in easier cases.

Another significant result related to the effect of law model on rankings of the importance of the three categories of facts: 'detailed rule facts', 'broad principle facts' and 'glue facts' (essential to the narrative but without legal significance). There were highly significant interactions between fact category and time, and between fact category, time and law model. These interactions were due to: a) increasing ratings over time for detailed rule facts; b) decreasing ratings over time for glue facts; c) a marginally significant interaction between the effects of time and law model on the ranking of broad principle facts, in the form of an increase over time by users of broad principles and a decrease over time for by users of detailed rules.

Heathcote and Close have since developed a constraint satisfaction network model along lines suggested by Simon (1998) and Thagard (2004), and have used it to simulate these results. This indicates that the greater utility of broad principles may be explained by the cognitive processes involved in legal decision making.

A paper reporting these results is available here: Coherence based reasoning and models of contract law. It will be presented at the Annual Conference of the Cognitive Science Society in Amsterdam, 30 July - 1 August, 2009.