This chapter provides the mutually beneficial importance of psychology's full participation in complexity science. Psychology's key contribution should be integrated psychological models of the individual mind situated in the social world. The chapter introduces an integrated social and developmental psychological model as one example of how to apply complex systems principles to integrate psychological theory. It describes a complex psychological system, a classic psychological theory, integrates modern theories and findings within the classic framework, and then implements the final model as a neural network. Attachment theory, and behavioral systems theory, is both an evolutionary and developmental psychological theory. Connections between psychological systems in the network are adjusted according to biologically realistic learning algorithms. Inspired by biological brains, neural networks can model dynamics such as nonlinear activation functions, thresholding, changing connections, and inhibition between psychological variables. Dynamics constitute adaptation if the changes occurring within the system are in response to an external environment.