This research investigated two aspects of intuition: preference and process. The underlying basis of preference for intuition defined by Jung in his theory of psychological types and measured by the sensing-intuition (SN) scale of the Myers- Briggs Type Indicator was explored in two areas: performance on ability tests and individual differences in use of intuition. Process of intuition is defined as the use of unconscious associations to guide decision making. A thinking aloud protocol technique was used to investigate differences in strategy between sensing and intuitive types on two ability tests. Test instructions and conditions were varied to investigate whether preference or ability underlies this difference. Results indicated that the SN difference is best characterised as a focus on different types of information - concrete reality vs. looking beyond reality to patterns, connections and possibilities. The finding that sensing types could modify their style suggested that this is due to a personality preference that can be overridden rather than an underlying ability difference. The nature of the SN difference was further explored by examining the differences predicted by type theory between the types in the use of intuition. This prediction contrasts with some process theories of intuition which expect few or no individual differences. Results indicated that intuitive types were more accurate and more likely to choose to use intuition than sensing types. Results suggested that preference for different types of information led to use of different strategies on the tasks. Intuitive types tended to focus on feelings of familiarity, which resulted in their accessing intuition in the form of unconsciously learnt associations. Sensing types preferred to focus on concrete information such as conscious memory of prior experience. The research has made contributions by evaluating the theory of psychological types, validating the sensing-intuition scale, and also by demonstrating the existence of individual differences in certain measures of intuition.