Unimanual skills as hand lateralization predictors

The skill of writing with the left or right hand is often taken as a hand lateralization predictor. Taking into consideration that such a manifestation is usually practiced, left-handedness often becomes 'concealed', making it harder to be phenotypically measured. The aim of this study is to determine the predictability of multiple manual skills in relation to the type of handedness. The sample of 756 primary-school students with the aid of Edinburgh Handedness Inventory showed that writing and drawing skills using a particular hand have a very clear mutual correlation (0.86 with the left-handed, and 0.50 with the right-handed). However, the correlation was not determined with other observed unimanual skills, such as throwing, using scissors, using a tooth brush, using a key and holding a glass. In addition to that, writing as such is not a reliable hand lateralization predictor. In relation to hand lateralization, writing shows a low determination coefficient with the left-handed, whereas for other skills R2 varies within the range 0.43-0.66. The numbers are similar to the right-handed, where R2 varies within the range 0.28-0.53, for all skills, except writing and drawing. A conclusion can be drawn that writing is not a reliable predictor of lateralization to left or right, but that those are skills in relation to which there is no cultural pressure.