Because early theoretical frameworks such as Piaget's stage model and social learning theory sought to explain the development and performance of imitation in terms of overall group trends, any evidence for individual differences in this behavior was until recently largely overlooked. Results of contemporary imitation studies have not only begun to acknowledge the presence of individual differences in imitative performance, but also challenge early cognitive developmental theories' proposal of an adherence of the capacity to imitate to a fixed progression of developmental stages. Likewise, such studies support the idea of stable cognitive variables underlying the capacity for imitation. Preliminary investigations of the stability of these variables within the individual have revealed some evidence suggesting that genetic influences may be at work. Additional research in this area will further explore the possibility for genetically influenced individual difference variables contributing to imitative ability.