Nature, nurture, and development: from evangelism through science toward policy and practice.

During the second half of the 20th century there was an immense increase in both empirical findings on, and conceptual understanding of, the effects of nature, nurture, and developmental processes on psychological functioning--both normal and abnormal. Unfortunately, the good science has also been accompanied by excessive polarizing claims and by unwarranted extrapolations. This article provides a summary review of the real gains in knowledge, outlines some of the misleading claims, and notes the potential for research and for science-led improvements in policies and practice. The need to bring about a better interpretation of genetic, psychosocial, and developmental research strategies and theoretical concepts is emphasized.