"Long before it's in the papers"
January 28, 2015


Lower IQ’s measured in spanked children

Sept. 24, 2009
Courtesy University of New Hampshire
and World Science staff

Chil­dren who are spanked have low­er IQs world­wide, ac­cord­ing to new re­search.

An in­ves­ti­ga­tor for the study ac­knowl­edged that at least part of this effect is due not to spank­ing it­self, but to so­ci­o­ec­o­nom­ic sta­tus: wealth­i­er fam­i­lies both spank less and man­age to raise higher-IQ chil­dren, though the first does­n’t nec­es­sarily cause the sec­ond.

American children who were spanked had a low­er cog­ni­tive abi­lity score four years later, re­search­ers say. (Cour­tesy Mur­ray Straus)

None­the­less, the re­searcher, the Uni­vers­ity of New Hamp­shire’s Mur­ray Straus, said at least part of the ex­plana­t­ion for the find­ings is that the stress of cor­po­ral pun­ish­ment af­fects brain func­tion. This stress even­tu­ally pro­duces fear­ful, easily star­tled chil­dren, Straus said; these fac­tors in turn are as­so­ci­at­ed with low­er IQ, the most wide­spread meas­ure of gen­er­al in­tel­li­gence.

Straus is call­ing for laws against spank­ing. Twen­ty-four na­tions have al­ready passed such laws, though en­force­ment varies, said Straus, whose find­ings were pre­sented Sept. 25 at the In­terna­t­ional Con­fer­ence on Vi­o­lence, Abuse and Trau­ma in San Die­go.

Straus found that chil­dren in the Un­ited States who were spanked had low­er IQs four years lat­er than non-spanked youths.

Straus and Mallie Paschall of the Pa­cif­ic In­sti­tute for Re­search and Evalua­t­ion in Calver­ton, Md., also stud­ied what they called na­t­ionally rep­re­sen­ta­tive sam­ples of 806 chil­dren ages 2 to 4, and 704 ages 5 to 9. Both groups were retested four years lat­er. 

IQs of non-spanked chil­dren in the first group were five points high­er four years lat­er than the IQs of those who were spanked, the sci­ent­ists found. IQs of chil­dren in the sec­ond age group who weren’t spanked were 2.8 points high­er four years lat­er than their non-spanked peers. 

IQ is de­fined as a per­son’s men­tal age divid­ed by their act­ual age, times 100. Thus the av­er­age IQ is 100. Scient­ists often label people with scores above 130 as gift­ed; those be­low 70, as re­tarded.

“The more spank­ing, the slow­er the de­vel­op­ment of the child’s men­tal abil­ity. But even small amounts of spank­ing made a dif­fer­ence,” Straus said. The re­search­ers al­so found a low­er na­tional av­er­age IQ in na­tions where spank­ing is more prev­a­lent. His anal­y­sis in­di­cates the strongest link be­tween cor­po­ral pun­ish­ment and IQ was for those whose par­ents con­tin­ued to use cor­po­ral pun­ish­ment even when they were teenagers.

Cor­po­ral pun­ish­ment has been de­creas­ing world­wide, which may sig­nal fu­ture gains in IQ, Straus pre­dicted. “Some of the 24 na­tions that pro­hib­it cor­po­ral pun­ish­ment by par­ents have made vig­or­ous ef­forts to in­form the pub­lic and as­sist par­ents in man­ag­ing their chil­dren. In oth­ers lit­tle has been done to im­ple­ment the pro­hib­ition,” Straus said.

“N­ev­er­the­less, there is ev­i­dence that at­ti­tudes fa­vor­ing cor­po­ral pun­ish­ment and ac­tu­al use of cor­po­ral pun­ish­ment have been de­clin­ing even in na­tions that have done lit­tle to im­ple­ment the law and in na­tions which have not pro­hib­ited cor­po­ral pun­ish­ment.”

The findings are also to appear in the Jour­nal of Mal­treat­ment, Ag­gres­sion and Trauma. 

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Children who are spanked have lower IQs worldwide, including in the United States, according to new research. An investigator for the study acknowledged that at least part of the explanation not due directly to spanking, but to socioeconomic status: wealthier families both spank less and manage to raise higher-IQ children, though the first doesn’t necessarily cause the second. Nonetheless, the researcher, the University of New Hampshire’s Murray Straus, said at least part of the explanation for the findings is that the stress of corporal punishment affects brain function. This stress eventually produces fearful, easily startled children, Straus said; these factors in turn are associated with lower IQ, the most widespread measure of general intelligence. Straus is calling for laws against spanking. Twenty-four nations have already passed such laws, though enforcement varies, said Straus, whose findings were presented Sept. 25 at the International Conference on Violence, Abuse and Trauma in San Diego. “All parents want smart children. This research shows that avoiding spanking and correcting misbehavior in other ways can help that happen,” Straus said. Straus found that children in the United States who were spanked had lower IQs four years later than non-spanked youths. Straus and Mallie Paschall, senior research scientist at the Pacific Institute for Research and Evaluation in Calverton, Md., studied “nationally representative” samples of 806 children ages 2 to 4, and 704 ages 5 to 9. Both groups were retested four years later. IQs of children in the first group who weren’t spanked were five points higher four years later than the IQs of those who were spanked, the scientists found. The IQs of children in the second age group who weren’t spanked were 2.8 points higher four years later than their non-spanked peers. IQ is defined as the ratio of a person’s mental age to their chronological age, times 100. Thus the average IQ is 100. “The more spanking, the slower the development of the child’s mental ability. But even small amounts of spanking made a difference,” Straus said. The researchers also found a lower national average IQ in nations where spanking is more prevalent. His analysis indicates the strongest link between corporal punishment and IQ was for those whose parents continued to use corporal punishment even when they were teenagers. Corporal punishment has been decreasing worldwide, which may signal future gains in IQ, Straus predicted. “Some of the 24 nations that prohibit corporal punishment by parents have made vigorous efforts to inform the public and assist parents in managing their children. In others little has been done to implement the prohibition,” Straus said. “Nevertheless, there is evidence that attitudes favoring corporal punishment and actual use of corporal punishment have been declining even in nations that have done little to implement the law and in nations which have not prohibited corporal punishment.”