Comments on Joseph's review of the genetics of attention deficit disorder, demonstrating errors of scientific logic and oversight of relevant research in Joseph's argument. Argues for the validity of twin studies in supporting a genetic link for ADHD and for the complementary role of nature and nurture in the etiology of the disorder. (JPB)

Answers the most important criticisms by Faraone and Biederman in their critique of Joseph's analysis of evidence supporting a genetic basis of attention deficit hyperactivity disorder. Argues that possible genetic and environmental influences in ADHD twin studies are confounded, obscuring inferences about genetic factors. (JPB)

Examines the empirical evidence cited in favor of the operation of genetic factors in attention-deficit hyperactivity disorder and argues that the evidence does not support a role for genetic factors in the disorder. Discusses problems compromising family, twin, and adoption studies. (JPB)

Identified subjects' handedness and family handedness (genetic variables) and college major (environmental variable); and tested subjects on the Vandenberg Mental Rotation Test. Found that right-handed females with non-right-handed relatives and with science or math majors outperformed other females and equaled the performance of males on the…

Identifies three main strengths of Casey's spatial ability model, but notes that a study by McKeever found different results concerning the relationship between familial handedness and females' mental rotation ability. Considers the use of a familial handedness measure to be a weakness of the model because handedness might not be an inherited…

Notes Halpern's general support for Casey's model. Addresses differences in Casey's and McKeever's findings on familial handedness and females' spatial ability by performing another experiment in which data are analyzed according to two different theoretical assumptions. Addresses the question of the heritability of handedness by noting that what…