An experimental study of collaborative reasoning in 86 7th-grade minority s
tudents from an urban, low-income school was conducted. The students comple
ted items from the Test of Nonverbal Intelligence-Third Edition (TONI-3) an
d were asked to provide written explanations for their judgments. All stude
nts worked individually during the pretest and posttest phases of the study
. During the experimental phase, some students worked independently while o
thers worked in small, same-gender or mixed-gender groups. Significant impr
ovements in judgments were evident during the experimental phase for all gr
oups except the single-gender female group. The mixed-gender group reached
the ceiling level of performance and outperformed both the students who wor
ked independently and the collaborative, single-gender female group during
the experimental phase. Posttest judgment scores declined and were not sign
ificantly different from pretest scores for any group. Significant improvem
ents in written explanations for judgments were evident during the experime
ntal phase and were maintained on the posttest by all groups. The students
who collaborated had higher percentages of fully correct explanations on th
e posttest than students who worked alone. Collaborative experiences were b
eneficial for students' reasoning about unfamiliar, moderately difficult, n
onverbal problems.