Aptitude by treatment interactions and matthew effects in graduate-level cooperative-learning groups

The authors investigated the role of group composition on cooperative-learning groups. Participants were 275 graduate students enrolled in 15 sections of an introductory-level education research course who, through a modified stratified random assignment procedure, formed 70 groups ranging in size from 2 to 7. Using group as the unit of analysis revealed a small-to-moderate positive relationship between research aptitude (i.e., mean midterm and final examination scores) and group outcomes (i.e., scores on the article critiques and proposals)—the relationships involving the midterm scores suggested a Matthew effect, with respect to group outcomes. The authors found a positive relationship between degree of group heterogeneity (i.e, variability of the individual midterm scores) and scores on the article critique. A quadratic trend defined the relationship found between group size and performance on the article critique. Finally, a Treatment (i.e., group heterogeneity level) x Aptitude (i.e., mean midterm group performance) interaction was found with respect to the article critiques scores. Implications are discussed.