In a study just published in the Journal of Consumer Research, marketing professors Itamar Simonson of Stanford University and Aner Sela of the University of Florida, Gainesville, conducted studies of the product preferences of pairs of identical twins and compared them to pairs of fraternal twins — who are no more genetically similar than any other siblings. Repeatedly, they found that the identical twins were likelier to exhibit the same tastes across a broad range of products, particularly when it came to chocolate, mustard, hybrid cars, science fiction movies and jazz…

To dig deeper, Simonson and Sela thus conducted subtler psychological tests to explore various tendencies exhibited by their twin pairs. Among them: an avoidance of extreme choices or behaviors in favor of compromise; a preference for sure things over gambles; and a habit of exhausting all options before making a decision as opposed to deciding more quickly, if perhaps less thoroughly. These, of course, are all behaviors that undergird consumer decisions and they’re harder for twins simply to observe and mimic in each other than, say, whether to go for French’s or Maille in the mustard aisle. As the researchers expected, the identical twins were far more similar in such fundamental behaviors than the fraternals were.