International Journal of Comparative Psychology

Comparative and developmental psychology have impacted one another for well over 100 years. Researchers have studied developmental processes of humans and nonhumans to formulate evolutionary theories and to determine the contributions of hereditary and experiential factors at ontogenetic and phylogenetic levels. We discuss current directions in comparative and developmental research that attend to micro-developmental processes and ecological contexts as sources of variability in humans and nonhumans. This research has been a segue into studies of behavior that are integrative in scope, such the family of systems theories, which cross disciplinary boundaries. We present findings from our research on instrumental manual activity in human and nonhuman primates from a systems perspective, and argue that integrative systems approaches hold promise for understanding individuals and development of behavior across species.