The Trouble with Twin Studies questions popular genetic explanations of human behavioral differences based upon the existing body of twin research. Psychologist Jay Joseph outlines the fallacies of twin studies in the context of the ongoing decades-long failure to discover genes for human behavioral differences, including IQ, personality, and the major psychiatric disorders. This volume critically examines twin research, with a special emphasis on reared-apart twin studies, and incorporates new and updated perspectives, analyses, arguments, and evidence.

part I|150 pages

Studies of Reared-Apart Twins

chapter 1|14 pages


chapter 2|44 pages

Studies of Reared-Apart Twins

Origins, publications, and scandal

chapter 3|14 pages

Studies of Reared-Apart Twins

The Critics Respond

chapter 4|27 pages

Studies of Reared-Apart Twins

Basic Assumptions and Potential Fallacies

chapter 5|26 pages

The Minnesota Study of Twins Reared Apart I

Biases, Assumptions, and Other Problem Areas

chapter 6|23 pages

The Minnesota Study of Twins Reared Apart II

IQ and Personality Studies

part II|54 pages

Studies of Reared-Together Twins

chapter 7|26 pages

The Mzt–Dzt Equal Environment Assumption

The Achilles Heel of the Classical Twin Method

chapter 8|26 pages

Twin Research in Psychiatry

part III|48 pages

Approaching a Post-Behavioral- Genetics Era?

chapter 9|15 pages

Molecular Genetic Research

The Ultimate Test of Genetic Interpretations of Twin Studies

chapter 10|14 pages

The Crumbling Pillars of Behavioral Genetics

chapter 11|11 pages

A Human Genetics Parable

chapter 12|6 pages

Summary and Conclusions