Genetic and environmental explanations of developmental change are often pitted against each other. Pick a particular aspect of mental life--such as language, emotion, or motor skills--and give your own assessment of the relative importance of genes and environment in its development. Discuss the relevance of the "interactionist approach."

What is the difference between stage-based and incremental theories of developmental psychology?

Explain why a longitudinal, experimental study is scientifically more rigorous than a cross-sectional, observational study. Discuss the costs and concerns that prevent such studies from being conducted more frequently.