Esther Thelen

We propose that connectionism and dynamic systems theory are strong contenders for a general theory of development that holds true whatever the content domain. We illustrate, through our own career narratives, the origins of these theories in motor and language development. We situate connectionism and dynamic systems among other classic and contemporary theories and conclude that, although there are meaningful differences, these differences pale in relation to the shared assumptions about the fundamental processes and mechanisms of change.

The evolutionary scenario described in this target article parallels developmental patterns observed in human infants. Early vocalizations are largely expressive, manual control develops more rapidly than intentional vocal articulation, and vocal and manual activity are linked. In ontogenetic development, language is strongly rooted in bodily action and gesture.

Piaget's (1952) question of how the adult mind emerges from the sensorimotor infant is still the framing issue for developmental psychology. Here I suggest that real‐life skill is better understood if the sensorimotor origins of cognition are not abandoned. Skilled people are not only better at both abstract and logical thinking but also at processing the world “online” and, most important, seamlessly and rapidly shifting between the two modes. I illustrate the tight coupling between action, perception, and cognition in early life and propose that this coupling remains but becomes more flexibly adaptive. Further, I show that the language of dynamics is appropriate to capture these mind‐body‐world interconnections.

The onset of directed reaching demarks the emergence of a qualitatively new skill. In this study we asked how intentional reaching arises from infants' ongoing, intrinsic movement dynamics, and how first reaches become successively adapted to the task. We observed 4 infants weekly in a standard reaching task and identified the week of first arm-extended reach, and the 2 weeks before and after onset. The infants first reached at ages ranging from 12 to 22 weeks, and they used different strategies to get the toy. 2 infants, whose spontaneous movements were large and vigorous, damped down their fast, forceful movements. The 2 quieter infants generated faster and more energetic movements to lift their arms. The infants modulated reaches in task-appropriate ways in the weeks following onset. Reaching emerges when infants can intentionally adjust the force and compliance of the arm, often using muscle coactivation. These results suggest that the infant central nervous system does not contain programs that detail hand trajectory, joint coordination, and muscle activation patterns. Rather, these patterns are the consequences of the natural dynamics of the system and the active exploration of the match between those dynamics and the task.