New evidence of dysgenic fertility for intelligence in the United States Richard Lynn a, * , Marian Van Court b a University of Ulster, Coleraine, County Londonderry, Northern Ireland, BT52 1SA, United Kingdom b Future Generations, 32-1 Briarwood Lane, Marlborough, MA 01752, USA Received 26 October 2001; received in revised form 4 August 2003; accepted 3 September 2003 Abstract Data from the General Social Survey (GSS) collected in the years 1990 – 1996 are examined for the relationship between fertility and intelligence as measured by vocabulary. The results show that the relation between fertility and intelligence has been consistently negative for successive birth cohorts from to 1900 to 1979, indicating the presence of dysgenic fertility for all of the 20th century studied thus far. The most recent cohort for which fertility can be regarded as complete is that born in the years 1940–1949. In this cohort, the decline of genotypic intelligence arising from the negative association between intelligence and fertility is estimated at .90 IQ points per generation. The decline of genotypic intelligence of Whites is estimated at 0.75 IQ points a generation. D 2004 Elsevier Inc. All rights reserved. Keywords: Intelligence; Dysgenic fertility 1. Introduction For almost a century and a half there has been concern that there is a negative association between people’s intelligence and their number of children. A negative association of this kind is known as dysgenic fertility. The reason it has aroused concern is that it would entail a decline in genotypic intelligence, i.e., the genetic quality of the population in respect of intelligence. In the 19th century this concern was voiced by Galton (1859) and in the earlier decades of the 20th century by Cattell (1937), Fisher (1929), and Muller (1963), among many others. Evidence for the presence of dysgenic fertility in the economically developed nations for the last 150 years or so and in most of the rest of the world during 0160-2896/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.intell.2003.09.002 * Corresponding author. Tel.: +44-117-303-9058. E-mail address: lynnr540@aol.com (R. Lynn). Intelligence 32 (2004) 193 – 201