Awareness of the knowledge of learning partners is not always sufficiently available in collaborative learning scenarios. To compensate, the authors propose to provide collaborators with partner knowledge awareness by means of a visualization tool. Partner knowledge awareness can be used to adapt messages toward the partner. This study investigated the cognitive consequences of message adaptation on producers. The authors chose a simulated collaboration scenario in order to dissociate the producer effect from recipient and collaboration effects. Results on 42 participants that had been randomly assigned to either the partner knowledge awareness condition (partner and own knowledge visualized) or the control condition (only own knowledge visualized) are reported here. Participants in the partner knowledge awareness condition adapted their contributions according to the visualized partner's knowledge and benefited with regard to the acquisition of elaborated knowledge. (Contains 5 tables and 1 figure.)