Co-discovery learning shares many principles with constructive interaction, but in addition, has a list of spesific tasks and includes a reflection on the task difficulty after each task. Sue Kennedy and her colleagues used this method in evaluating various communication systems by making two users cooperate and discovering how to use a new system by trial and error. The experimenter gives a list of tasks to the users and leaves them performing the tasks. After the users have completed a task, the experimenter immediately asks them to jointly assess the difficulty of the task. Both the discovery and the jointly made assessment give valuable information on the usability problems of the system.