The following is an exerpt from a review article in the "Connections" section of the March 1995 edition of "The Menninger Letter," a newsletter for mental health professionals. The study in question is Zvi Strassberg et al "Spanking in the Home and Children's Subsequent Aggression Toward Kindergarten Peers," Development and Psychopathology, Vol. 6, No. 3, Summer 1994, pp. 445-461.
"On reviewing earlier studies, a group of researchers headed by Zvi Strassberg of Vanderbilt University found indications that physically disciplined children became more aggressive than those who had not been spanked. These researchers theorized that children punished with physical aggression - even spanking - may in turn learn how to control other children with physical coercion. Parents who refrain from physical punishment may reduce their child's risk of becoming aggressive."
"Strassberg's own study involved 273 kindergarten children and their parents from several schools in two states (Tennessee and Indiana). The group was representative for gender and race."
"Through questionaires and oral interviews, parents reported how they had disciplined their children during the previous year. The children were then watched in the classroom and on the playground by trained observers who knew nothing about how the children had been disciplined."
"The children's behavior indicated that spanking is associated with higher levels of aggression toward peers. Children whose parents use more violent punishment are even more aggressive".