This paper describes the design and impact of a face-to-face Computer Supported Collaborative Learning activity named Collaborative Answer Negotiation Activity (CANA). CANA primarily involves face-to-face interactions among students supported by wirelessly interconnected mobile devices to solve collaboratively a set of multiple-choice questions. The learning outcomes of a CANA applied in two computer science courses are presented. Better results were obtained in a course where reasoning and deduction capacities were important than there were in a technical one where students were required to learn specific knowledge and apply it. A CANA design is described that will permit its reuse in various instructional scenarios. This design is defined as a collaborative learning activity pattern and is specified using IMS Learning Design, an established method of learning scenario description. The application of this method revealed the need to incorporate the notion of Joint Problem Space, a shared knowledge space that supports the collaborative work of the activity. (Contains 4 tables and 7 figures.)