This research examines the impact of Decision Support Systems (DSS) on the decision making process for preferential choice tasks. The potential impact of DSS on the decision process is evaluated in terms of how the system alters the decision maker's cognitive load. Competing hypotheses are developed based on the possible objectives of the decision maker with respect to decision effort and decision quality. One line of reasoning assumes that the DSS will be used in such a way as to maximise decision quality. The other asserts that the use of the DSS will be geared towards effort conservation. These hypotheses about the impact of the DSS on the decision process are tested in three experiments. The three studies employed concurrent verbal protocols to capture data about the decision process. In experiment 1 subjects were placed in either and aided or unaided decision setting and given problems of either five or ten alternatives from which to make a choice. The results showed that decision strategy changed as a results of the use of the decision aid. In general, subjects behaved as effort minimisers. There were no significant effects related to the amount of information processing. Experiment 2 was similar to experiment 1 except that subjects were given problems with either ten or twenty alternatives. The results were consistent with, though stronger than those of experiment 1. Almost all aided group subjects used Elimination by aspects strategy while the unaided group used a Conjunctive strategy. This is consistent with the notion of effort minimisation. There were no significant differences in the amount of information processing Experiment 3 was designed to test whether the results in experiments 1 and 2 were a due to the tendency of decision makers to minimise effort or because the aid was not powerful enough to induce additive processing. In this study the DSS was altered to both increase the support for the additive difference strategy and reduce support for the elimination by aspects approach. The results of experiment 3 show that decision makers tend to adapt their strategy to the type of decision aids available. There is evidence that if additive strategies are made sufficiently less effortful to use they will be employed. Similarly, when the degree of effort to follow a particular elimination strategy is manipulated decision makers tend to adapt in such a way as to minimise effort. Overall the results of the three experiments are consistent in demonstrating the adaptivity of decision makers to the types of support tools available to them. This adaptivity centres around the minimisation of decision effort. It appears that decision makers are highly conscious of the effort required to make decisions and work in such a way as to minimise that expenditure. When faced with the use a decision aid they appear to calibrate their own decision effort to that provided by the decision aid. There is some evidence that sufficient changes in the relative effort required to use various strategies can lead decision makers to follow more effortful approaches than they might otherwise consider. The precise nature of this effort-accuracy relationship needs to be studied more closely. The basic contribution of the dissertation has been to provide a formal approach for the study of DSS, based on concepts drawn from behavioural decision theory and information processing psychology. This work also has implications for behavioural decision theorists, consumer researchers and practical implications for the development of DSS in preferential choice settings. / Business, Sauder School of / Graduate