This study examined the effects of certain contextual linguistic variables on the logical performance of subjects in grades 4, 6, and 12 of selected British Columbia schools as well as some theoretical problems underlying assessment of the development of logical abilities. The task consisted of 27 syllogistic problems based upon the information contained in three narrative texts, a fantasy passage, a realistic passage, and a contractual passage. The logical problems were varied for argument type, negation, conditional statement type, and the mode of answer required. These problems were supplemented by three questions designed to elicit subjects' metacognitive awareness of the narrative properties of the texts, and a question examining subjects' understanding of the purpose of the test itself. The main findings concerned significant interactions between subject groups and treatment variables. Further analysis of the data revealed complex interactions between contextual and logical variables. It was concluded that a shift of emphasis was necessary away from structuralist approaches to the development of reasoning abilities toward models sensitive to the various discourse worlds entered by subjects when working on logical problem tasks. (Author/AMH)