The measurement of hand preference: a validation study comparing three groups of right-handers.

Three groups of right-handers were identified using the Edinburgh Handedness Inventory. Exclusive strong right-handers (Rs: N = 18) reported that they always used the right hand for eight or more of the 10 activities, and usually used the right hand for the remainder. Exclusive weak right-handers (Rw: N = 15) usually used the right hand for three or more activities, and always used the right hand for the remainder. Predominant right-handers (Rp: N = 18) preferred the right hand for most items, but used the left hand for at least one activity. These groups did not differ on three measures of relative skill of the two hands: peg-moving, tapping and dotting. Groups Rs and Rw were also indistinguishable in terms of the hand used for reaching for cards placed in different spatial positions. However, the reaching measure did discriminate group Rp, which included some individuals who reached predominantly with the left hand. It is concluded that preference batteries should quantify degree of hand preference in terms of the number of activities for which a preference is shown, ignoring the distinction between 'usually' and 'always'. The behavioural reaching measure shows promise as a method for providing a unitary scale of hand preference.