Objective: Substitute fathers are often reported to commit child abuse at higher rates than birth (i.e., putative genetic) fathers. Due to the paucity of studies, especially in developing countries, and to some conflicting results from developed countries regarding the identity of perpetrators of less extreme forms of physical abuse of children in…

The relation between intelligence and birth order was shown in a recent publication [Bjerkedal, T., Kristensen, P., Skjeret, G. A. & Brevik, J. I. (2007). Intelligence test scores and birth order among young Norwegian men (conscripts) analyzed within and between families. "Intelligence," 35, 503-514] to be negative. Subjects in this…