Many citizens misunderstand the actions of persons with brain injury, and these misunderstandings hamper rehabilitation. A specific misunderstanding is where people misattribute behaviours resulting from brain injury to the injured person's personality or life stage (e.g., adolescence). The present study examined if this pattern is explained by the Abnormal Conditions Focus model of attribution, which claims that attributions for behaviours reflect whether the behaviours are normal for the person (Consistency) and the culture (Consensus). Scenarios described an adolescent with brain injury performing four undesirable behaviours and then indicated whether the behaviour was normal or not normal for the person prior to injury and normal or not normal for that person's culture. For each of the four behaviours, students (n = 136) rated three attributions: brain injury, personality and adolescent norms. Participants attributed the behaviours more to brain injury and less to personality when the behaviours were not normal for that person than when they were normal for the person. They attributed the behaviours more to adolescence when the behaviours were normal for the person's culture than when they were not normal for the culture. Rehabilitation implications include assessing individuals' premorbid behaviour to enable citizens and less experienced professionals to make more accurate attributions for behaviours and target treatment more effectively.