Networks are based on student recall of interactions.

<p>Links in these networks are based on the assumption that students remember interactions they had as a part of studying (a). Once a week for nine weeks, sessions were set up so students could indicate the names of fellow students with whom they remembered having communicated about problem solving in physics. Students were asked to consider only the preceding week, and they responded online (b). For each session, the responses were used to create a directed network that models the interactions between students. In each network a directed link exists from a node B to a node A if student B indicated student A in the corresponding session. (c)