The purpose of the current study was to look at the effects of a stressor, in the form of a time constraint, on the learning of different stimulus-response (S-R) mappings. Effects of a speed stressor on performance were measured in terms of reaction time (RT) and percentage of errors. Results showed that the speed stressor reduced RT for all S-R mappings, with this decrease being more for incompatible than compatible mappings. However, there was a speed-accuracy tradeoff in which more errors (incorrect response choices) were made in the incompatible mapping conditions. Examination of the errors revealed that subjects revert back to responding with a spatially compatible mapping under the presence of a speed stressor. These results imply that a speed stressor does have an effect on performance with S-R mappings that vary in degree of compatibility and should be taken into consideration when designing display and control interfaces.