Original text - Engels - you ensure that students promote one another's success face to face

Doing so entails cognitive processes such as verbally explaining how to solve problems, teaching one's knowledge to classmates, and connecting present with past learning. It also leads to such interpersonal processes as challenging one another's reasoning and conclusions, modeling, and facilitating efforts to learn. The verbal and nonverbal responses of other group members provide important feedback as to a student's performance. Students also get to know each other on a personal as well as a professional level. To obtain meaningful face-to-face interaction, the size of groups needs to be small (two to four members).