A multitrait-multimethod design provided the basis for variable selection and analysis on the nature of cognitive impulsivity in natural classroom settings. Observational measures were developed for field dependence-independence, as well as for low- and high conceptual level to determine their ecological validity. They were designed to form an inferential hierarchy for each of the styles, completing the multitrait-multimethod matrix. Teacher rating scales, global measures, and behavior check lists were developed. Subjects were six female and six male adult student prison inmates (mean age = 31.6, mean grade level = 11). Observations were made by viewing a 40-minute videotape of students engaged in classroom discussion and problem solving activities. The reflection-impulsivity style construct emerged as an ecologically valid and parsimonious descriptor of a component of student behavior. The unusually high rank-order correlations obtained and the patterns which emerged from the matrix suggest justification for use, although results in terms of correlations must be viewed as tenuous in view of the small number of subjects involved. (PN)