Participants: Doreen Bartlett, PT, PhD, and authors James Cole Galloway, PT, PhD, and Jill C. Heathcock, PT, PhD. Moderator: Rebecca L. Craik, PT, PhD, FAPTA, PTJ Editor in Chief. Reevaluate the principles upon which development occurs—and look not just at the brain, and not just at behavior, but at “brain behavior.” Bartlett, Heathcock, and Galloway discuss the implications of “Exploring Objects With Feet Advances Movement in Infants Born Preterm: A Randomized Controlled Trial” (October 2009 issue). This discussion is dedicated to Dr Esther Thelen, the developmental psychologist who “applied dynamics systems theory—which the public knows as chaos theory—to the study of movement of babies,” explains Craik.