Efficacy research in early intervention: an elusive quest?

The last two decades have given rise to the development of a large range of Early Intervention programs catering for the needs of infants and young children who are environmentally disadvantaged, biologically 'at risk' or who have established disabilities. From the time programs of this type were first established, researchers have been struggling to demonstrate their efficacy. These attempts have been impeded by ethical concerns and methodological difficulties. This paper presents a review of the efficacy literature in Early Intervention. While questioning the value of the 'quest' to establish efficacy per se, it highlights the importance of identifying critical program components and of testing the impact of these components through carefully controlled short and long-term research.