Esther Stillman Thelen, a developmental psychologist who applied dynamic systems theory, popularly called "chaos theory," to the study of how babies learn to walk and interact, has died. She was 63.
Thelen, who conducted research at Indiana University Bloomington for 19 years, died Dec. 29 of cancer at Bloomington Hospital.
The psychologist, who was president of the Society of Research in Child Development, saw a child's development more akin to a jazz improvisation than to a biological process driven by genes, her colleagues said.
"Dynamic systems theories depart from conventional approaches," she told Indiana University's Research and Creative Activity journal in 2003, "because they seek to understand the overall behavior of a system not by dissecting it into parts, but by asking how and under what circumstances the parts cooperate to produce a whole pattern."
Her work has had a major effect on physical therapy for babies and young children, prompting therapists to design individual exercises tailored to a child's body rather than using standard exercises for all children of a given age.
Prior to Thelen's work, the conventional thinking of how babies develop motor skills was described as "stages and phases." Scientists believed that infants reached, walked and made other advancements according to when the corresponding parts of the brain matured.
But Thelen and others demonstrated, through watching and recording babies' behavior, that the accomplishments reflected a complex interplay of factors involving physical changes in their bodies and their external environment.
New skills, she found, arise as continuing solutions to problems -- how to look at an interesting sight, retrieve an interesting object, explore a new place or engage another child.
"It's all part of baby problem-solving," she once told Newsweek, explaining why some infants skip crawling and simply scoot on their bottoms. The goal, she said, is not crawling for its own sake "but to get someplace."
Her specific studies included infants learning two-handed reaching, intra-limb coordination such as kicking to move mobiles and development of gestures and speech.
Her work influenced experts not only in psychology but also in kinesiology, cognitive science, computer science, robotics and neuroscience.
Born in Brooklyn, N.Y., she attended Antioch College in Ohio; she earned her bachelor's degree from the University of Wisconsin in Madison and master's and doctorate from the University of Missouri, where she worked in the psychology department from 1977 to 1985.
She is survived by her husband, David, a history professor at Indiana University Bloomington; a daughter, Jennifer, of Richmond, Calif.; a son, Jeremy, of Providence, R.I.; a sister, Harriet Saeck, of Sacramento; and one grandson.
Services are planned Jan. 16 on the Bloomington campus. Donations may be sent to the Esther Thelen Memorial Fund, Indiana University Foundation, care of Psychology Department, 1101 E. 10th St., Bloomington, IN 47405, or to a children's charity of the donor's choice.