This study was part of a larger study investigating the influence of group collaboration during a group assessment on performance of the group and subsequent widespread performances. This study compared the verbal interactions of students while they completed a science assessment in small collaborative groups with their performance on the same test administered individually. What their verbalizations revealed about their cognitive processes and how verbalizations corroborated their performance scores and helped clarify their responses were analyzed. From a sample of 662 seventh and eighth graders, a subsample of 6 students from each class (mainly eighth graders), for a total of 126 students, was selected. Group discussions during the assessment were videotaped and later coded for analysis. Results indicated that analyzing verbal interactions might be a useful source of information about students' thinking to supplement individual test results. More than half of the students gave evidence of their degree of comprehension during group discussion, and a substantial portion gave different information in their verbal interaction than they gave on the individual test. The less information they gave on the test, the more useful the verbal interaction was in revealing their understanding. An appendix gives sample questions from the hands-on test. (Contains 5 tables and 21 references.) (SLD)