In this paper, we introduce a novel type of persuasive system aimed at orienting a group conversation in a casual setting. The system is based on a tabletop display complemented by a limited speech recognition system (a word spotter). It affects group behavior indirectly by presenting on the shared interface contextually appropriate visual material in a way reminiscent of the tradition of advertising: attention-catching, evocative, and cognitively stimulating. The system is meant to be used in the context of a museum visit. The purpose is to influence a group of friends so that they discuss their museum experience, while sitting at the museum café after the visit. Results show the system in the current version has a moderate effect on group behavior and provide indications for promising improvements.