This study investigated the speed of encoding and rotation of images during simple spatial rotational operations to discover any similarities or differences in groups of differing spatial ability. This project was subdivided into five basic subproblems. First, research was done to arrive at a simple, easily testable information processing model that could describe both the encoding and rotation components of spatial thought. Second, a computer software/hardware package was developed to measure reaction times of encoding and rotational tasks using equipment that would be affordable to the average high school science teacher. Third, the instrument was field tested with high school students. Fourth, 37 students from a field of 107 biology and earth science students were identified as being of high or low spatial ability. Finally, these students were tested with the developed instrument to investigate more fully the roles of encoding and mental rotation during spatial activity. The purpose of this project was to develop a working model of spatial thought so that it might be of use in persuading teachers to use intervention strategies on a more regular basis in the classroom. A problem section, literature review, methodology, results, conclusion, implications, and recommendations are included. Appended is a listing of the computer program used in this study. (KR)