UNIVERSITY PARK, Pa., May 12 -- Pennsylvania State University issued the following news release:

UNIVERSITY PARK, Pa. - As toddlers age into the preschool years, their dependency on their parents usually begins to ebb. However, a new study led by Penn State researchers has revealed that physically or psychologically aggressive parenting, such as spanking or shouting, can disrupt this pattern to the detriment of both child and mother, with the child requiring more external regulation, rather than less, as they age.

The research, led by doctoral student Jianing Sun and Professor of Psychology Erika Lunkenheimer and published in Child Development, validates part of a long-standing theory that parents act as the primary physiological regulat...