The psychometric properties of a paper-and-pencil instrument for assessing individual differences in cerebral dominance are explored. The instrument, Your Style of Learning and Thinking (SOLAT), contains 50 multiple-choice questions. The study subjects consisted of three groups: 235 undergraduate and graduate students, 124 undergraduate and graduate students, and 74 adults who had sustained brain injury after the age of 13 years. The latter group, who were enrolled at a community college, possessed normal fluid intelligence. The study was conducted in three phases: the first phase examined the SOLAT's construct validity; the second phase assessed the SOLAT's internal consistency and test/retest reliability coefficients; and the third phase further studied the SOLAT's construct validity by comparing the performance of brain injured and normal adults. Contrary to the predictions of cerebral dominance theory, a principal factor analysis for construct validity revealed a seven-factor solution. Assessment of the instrument's internal consistency and test-retest reliability indicated low to moderate correlations for these aspects. The further assessment of construct validity indicated that, with one exception, the instrument found no significant differences between the performances of brain-injured and normal adults. These results do not support the notion of hemisphericity, at least as measured by the instrument involved. This instrument should not be used by educators to differentiate students in terms of preferred mode of processing. Moreover, it is concluded that instructional planning that focuses on hemisphericity only detracts from more important sources of individual differences (such as attention and concentration, coding, and use of cognitive strategies). A 36-item list of references and six data tables are included. (TJH)