While the social cognitive theory suggests that a group's efficacy belief enhances its performance, emerging evidence indicates that this relationship is more complex than it appears to be. This study explores the boundary conditions of this relationship using the data of 389 employees from 41 work groups in a manufacturing company in South Korea. The results show that group efficacy is positively related to group performance and that this relationship is stronger when members are generally incompetent than competent. We also found that a bottleneck, which is operationalized as a group's minimum competency, in an efficacious group is at least one condition that forms a negative relationship between group efficacy and its performance.
Keywords: group competency; group composition; group efficacy.