*Department of Psychology, University of Pittsburgh, Pittsburgh, PA;

†The Norwegian Center for Child Behavioral Development, Oslo, Norway.

Address for reprints: Julia S. Feldman, MS, Department of Psychology, University of Pittsburgh, 4425 Sennott Square, 210 South Bouquet St, Pittsburgh, PA 15213; e-mail: julia.feld[email protected].

This work was supported by the Research Council of Norway (grant 202438/S20).

Disclosure: The authors declare no conflict of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.jdbp.org).

Ethical approval: The study is approved by the Regional Committees for Medical and Health Research Ethics and the Norwegian Social Science Data Services (approval numbers S-06067; 2009/224a).

See the Video Abstract at www.jdbp.org