In this article, the creator of the transactional model and a colleague give an overview of how the model emerged as well as its principal elements. For most of the 20th century, scientists believed that brain damage was the cause of a child's cognitive, social, or emotional problems. Later, researchers found that babies were likely to have developmental problems if they were raised in a high-risk family (e.g., in poverty). Thus, these problems were found to be not only biological but social as well. On the basis of this new data, the transactional model of development was created. The model combines influences of the child's biological heritage and life experience in a dynamic system. In particular, the behavior and competence of the child is seen as a function of how the parent reacts, not as an intrinsic characteristic of the child. This is evident in a three-part sequence: 1) infants stimulate their parents; 2) parents impose some meaning system on the input; and 3) parents then react with some form of caregiving. Where relationships are problematic, intervention should be directed at one or more of these three parts. The authors conclude that the life course of any particular child includes many influences that have power to change things for the better or worse; hence, children are neither doomed nor protected by their own characteristics or by the characteristics of their caregiver alone.