Although individuals may use different strategies in order to solve reasoning problems, few attempts have been made to understand the processes that lead to strategy choice. One exception to this is work with the sentencepicture verification task in which it has been found that high spatial ability individuals tend to use a strategy that involves spatial representations while low spatial ability individuals tend to use a strategy that involves verbal representations. The first study reported here attempted to see whether these findings would generalize to another simple reasoning task with a particularly inefficient spatial strategy. This was found not to be the case; low spatial ability individuals used the spatial strategy while high spatial ability individuals avoided using it. Three explanations were suggested for this based upon (a) spatial ability, (b) intelligence or (c) knowledge. Results of two further studies favoured the spatial ability explanation; individuals do not have explicit prior knowledge of the most effective strategy for this task, and the level of spatial ability determines the degree to which they are able to develop and evaluate the more effective non-spatial strategies.