Bandura?s theories of self- and collective efficacy are widely recognized in many fields, including psychology and management, but have been largely unnoticed by the Human-Computer Interaction (HCI) community. The purpose of this paper is to investigate how individual and group self-beliefs are formed prior to and during a group task and how they change as a function of time after the tasks. The empirical study reported on here looks for changes in self- and collective efficacy that might occur at two different times, to identify their different effects; these are immediately after a task is completed, and again ten days later. The conclusion is that memory deficiencies result in the maintenance of self- and collective efficacies that do not appropriately match the skills of group members and that this gap affects their ongoing performance.