Bouchard worked on twin study, particularly as part of the Minnesota Study of Twins Reared Apart. This work has included case studies, longitudinal studies, and large-scale quantitative analyses and meta-analyses. These studies attempt to determine to what role genes play medical and psychological outcomes, such as a personality or the heritability of IQ. One of Bouchard's case studies was Jim Springer and Jim Lewis, twins who had been separated from birth and were reunited at age 39. Bouchard arranged to study the pair, assembling a team and applying for a grant to the Pioneer Fund in 1981. According to The Washington Post, the twins "found they had each married and divorced a woman named Linda and remarried a Betty. They shared interests in mechanical drawing and carpentry; their favorite school subject had been math, their least favorite, spelling. They smoked and drank the same amount and got headaches at the same time of day." Bouchard has said that these two twins happened to be unusually alike, while most twins show more differences:
"There probably are genetic influences on almost all facets of human behavior, but the emphasis on the idiosyncratic characteristics is misleading. On average, identical twins raised separately are about 50 percent similar -- and that defeats the widespread belief that identical twins are carbon copies. Obviously, they are not. Each is a unique individual in his or her own right.
In 1994, he was one of 52 signatories of Mainstream Science on Intelligence, a public statement written by Linda Gottfredson and published in The Wall Street Journal. This statement was a response to what the authors viewed as the inaccurate and misleading reports made by the media regarding academic consensus on the results of intelligence research in the wake of the appearance of The Bell Curve earlier the same year. The following year, he was part of task force commissioned by the American Psychological Association which released a consensus statement on the state of intelligence research titled . Bouchard served as Associate Editor for the journals Behavior Genetics and Journal of Applied Psychology. Bouchard is the author of more than 170 publications. According to the Web of Science, Bouchard's works have been cited over 5500 times and he has an h-index of 33.
