In a previous study, we established that compared to a written case, a video case enhances observable cognitive processes in the verbal interaction in a postgraduate problem-based learning format. In a new study we examined non-observable cognitive processes using a stimulated recall procedure alongside a reanalysis of the data from the first study. We examined the development of shared cognition as reflected in collaborative concept link formation, an approach to connecting a series of concepts related to a particular topic. Eleven paediatric residents were randomly allocated to two groups. After both analysing the same written case vignette, one group watched a video of the case in the vignette and the other group read a written description of the video. Both groups then reanalysed the vignette. After the group sessions, time-logged transcripts were made of the verbal interaction in both groups and all residents individually took part in a stimulated recall procedure. Causal reasoning concept links were labelled as individual or collaborative depending on whether they originated from individual residents or were directly elicited by verbal utterances from others. The video led to a significantly increased frequency ratio (after intervention: before intervention) of collaborative concept links but did not affect the frequency of individual concept links. This novel process approach to chronological registration of concept link formation offered additional evidence that shared cognition by means of co-elaboration of concept formation is stimulated by the use of patient video recordings in small group learning.