Working with data from the PISA study (OECD, 2007), Lynn (2010) has argued that individuals from South Italy average an IQ approximately 10 points lower than individuals from North Italy, and has gone on to put forward a series of conclusions on the relationship between average IQ, latitude, average stature, income, etc. The present paper…

In this article, time effects on intelligence test scores have been investigated. In particular, we examined whether the "Flynn effect" is manifest in children from the middle and higher IQ distribution range, measured with a child intelligence test based on information processing principles--the Leiden Diagnostic Test. The test was administered…

The research described in this article addressed the question of why siblings commonly have different developmental outcomes despite their common beginnings. The studies analyzed behavioral development, especially through examination of deviant behaviors and intellectual development, by tracing siblings' different life histories. The work is based…