Marginal intelligence difference between handedness groups

Sammanfattning: Whether the hand you write with has any impact or says anything about you has been debated for hundreds of years. The most cited in the media today is an association between left-handedness and creativity. However, handedness has also been associated with intelligence, with a small advantage for those being right-handed, according to a systematic review. The present study compared intelligence, measured by the Wiener Matrizen Test, across groups who self-reported writing always with the right, always with the left, or sometimes with the left and sometimes with the right hand (ambidextrous), in a sample of 8,399 Swedish adults. The right-handed group had higher intelligence than both left-handed and ambidextrous groups, with an effect size for the right-left difference of 0.18 for males and 0.08 for females. Although of little consequence for any individual, such effects may have practical consequences at the group level, and should therefore be taken into account when comparing groups across demographic categories. Left-handedness is, for example, 23% more common among males than among females.