Online Q&A discussion forums have recently become important information resources for students and studies have shown that online discussion forums have a positive influence on learning outcomes. However, it remains unclear how the specific characteristics of these forums contribute to this effect. This paper employed a set of evaluative criteria based on the tenets social cognitive theory to classify Q&A discussion forums according to the features they provide and the quality of the user experience. Experiments were conducted to determine how the characteristics of online Q&A discussion forums influence discussion behavior, the quality of discourse, and learning performance. Statistical results reveal that students using more elaborate online Q&A discussion forums are more likely to actively participate in online discussions, engaging at a higher cognitive level, and enjoying superior learning performance when compared to those using forums that are more rudimentary.