Purpose - This empirical study tests hypothesized relationships between team effectiveness and a measure of shared cognition that quantifies the degree of similarity between knowledge of the actual group and beliefs about preferred group states. Design/methodology/approach - The proposed model of shared cognition is based upon the triadic structure of actual-ideal-ought cognitive representations employed within self-discrepancy theory. Self discrepancy theory proposes that the degree of discrepancy (similarity) between cognitive representations of the actual self and representations of both the ideal and ought self represents particular emotional situations. This study elevates the concept of a self-state representation to the group level by asking group members to list attributes associated with the actual, ideal and ought group-states (group-state representations). Shared cognition for 56 project teams is measured by comparing the actual group-state representations of each member with both the ideal and ought group-state representations of the other members. This extends the measurement of shared cognition beyond the aggregation of individual measures and creates the potential for capturing group level cognition structures that have the potential to evoke affect, influence motivation and impact outcomes. Findings - Hypotheses proposing a relationship between team effectiveness and both shared actual-ideal and shared actual-ought group-state representations, mediated by cohesion and confidence in the team's ability, respectively, are mostly supported. Originality/value - By examining the degree of similarity between perceptions of what currently exists (knowledge) and what is preferred (belief) this research examines evaluative cognitive structures that have the potential to evoke affect, influence motivation and impact on outcomes.