TUESDAY, Sept. 15, 2009 (HealthDay News) -- Children who are spanked as 1-year-olds are more likely to behave aggressively and perform worse on cognitive tests as toddlers than children who are spared the punishment, new research shows.
Though the negative effects of spanking were "modest," the study adds to a growing body of literature that's finding spanking isn't good for children.
"Age 1 is a key time for establishing the quality of the parenting and the relationship between parent and the child," said study author Lisa J. Berlin, a research scientist at the Center for Child and Family Policy at Duke University. "Spanking at age 1 reflects a negative dynamic, and increases children's aggression at age 2."
The study is published in the September/October issue of Child Development.
Berlin and her colleagues looked at data on 2,500 white, Mexican American and black children from low-income families. The data included parents' reports about their children's behavior, their use of spanking, as well as home visits by trained observers to document parent-child interactions at ages 1, 2 and 3.
About one-third of mothers of 1-year-olds reported they or someone in their household had spanked their child in the last week, while about half of the mothers of 2- and 3-year-olds reported that their child had been spanked.
The average number of spankings for 1-year-olds was 2.6 per week, while the average for 2-year-olds was nearly three.
The study found that children who were spanked at age 1 had more aggressive behaviors at age 2 and performed worse on measures of thinking abilities at age 3.
Being spanked at age 2, however, did not predict more aggressive behaviors at age 3, possibly because the spanking had begun at age 1 and by age 2 the kids were already more aggressive, Berlin said.
Researchers also looked at the effects of verbal punishment, defined as yelling, scolding or making derogatory comments. Verbal punishment was not associated with negative effects if the mother was otherwise attentive, loving and supportive.
Researchers controlled for family characteristics such as race, ethnicity, mother's age, education, family income and the child's gender.
Previous research has shown spanking is more common among low-income households than high-income households.
Researchers chose a sample of low-income families because some child behavior experts have argued that when spanking is "cultural normative" -- that is, it's expected for parents to use physical discipline -- the detrimental effects of spanking may be lessened.
"We did not find that," Berlin said. "Even in a sample of low-income people where presumably it's more normative to spank your kids, we found negative effects."
The study also found that mothers who said their children were "fussy" babies were more likely to spank them at ages 1, 2 and 3. But children who were more aggressive at 2 were not more likely to get spanked.
"The implication or the suggestion in past arguments is that some kids who are more aggressive or difficult to control might elicit more spanking, but that's not what we found," Berlin said.
Researchers found that black children were spanked and verbally punished the most, possibly because of cultural beliefs about the importance of respecting elders and in the value of physical discipline, or because parents feel they have to prepare their children for a racist and potentially dangerous world.
Of all the debates over child-rearing, spanking "definitely touches a nerve," Berlin said.
"It's a parenting practice that has been around for a long time, and that's also in transition," Berlin said. "In general, the use of spanking is going down. But there is also a contingent of people who really believe in it, who say that's how they were raised and it's a tradition they want to continue."
Elizabeth T. Gershoff, an associate professor in the department of human development and family sciences at University of Texas at Austin, said the study adds to a growing body of research showing negative effects of spanking.
"Almost all the studies point to negative effects of spanking," Gershoff said. "It makes kids more aggressive, more likely to be delinquent and to have mental health problems. The more kids are spanked, the more they are likely to be physically abused by their parents. This does not mean everyone who spanks physically abuses, but that risk is there."
Because children tend to mimic parental behaviors, it's possible spanking "creates a model for using aggression," Gershoff said. "Spanking is just hitting."
Less is known why spanking could inhibit cognitive development. One possibility is that parents who spank are less likely to use reasoning with their children, something that's good for development, Gershoff said.
The American Academy of Pediatrics has more on strategies of disciplining children without spanking.