Over the past half-century attachment theory has emerged as a driving force for research and practice across much of the developmental psychology community. Some of the most compelling empirical support for the biological basis of attachment theory has come from research with monkeys. This chapter highlights some contributions that my colleagues and I have made in generating this evidence by broadening the range of activities associated with attachment throughout development, exploring the relationship between behavioral patterns and a host of biological processes including some genetic factors, and characterizing the consequences of different expressions of attachment for the external social world that is progressively engaged throughout development. This body of nonhuman primate research has featured several important turning points, largely the product of certain unique combinations of colleagues and circumstances that served to generate major inflection points in shaping the direction and scope of the research described here.

This chapter describes some of the issues to be considered when dealing with longitudinal data. Longitudinal data can be defined as data gathered on a set of units over multiple time periods. Longitudinal data can be collected either prospectively or retrospectively, and data can be either qualitative or quantitative. Different ways of deriving repeated observations generate the three main types of longitudinal design: repeated cross-sectional surveys, panel surveys, and retrospective surveys. The world of longitudinal research is thus very heterogeneous. This chapter provides both a summary of advantages and disadvantages of each longitudinal design and some guidelines for authors and researchers.