Tobias Kalisch and colleagues recruited 60 participants who were all strongly right-handed according to the commonly-used Edinburgh Handedness Inventory (EHI), which asks people to indicate their favoured hand for several everyday activities. The participants then completed a range of computerised dexterity tests, including line tracing, an aiming task, and tapping (pictured left).
Consistent with their claims of right-handedness, the younger group of participants (average age 25 years) performed far better with their right hand on all the dexterity tests. By contrast, the middle-aged group (average age 50) performed just as well with either hand on the aiming task. And the two older groups (average age 70 and 80 years) performed just as well with either hand on all the tasks bar one.
Overall, performance tended to be poorer with increasing age, especially for the right hand. In other words, it seems we become more ambidextrous as we get older because our dominant hand loses its superior dexterity and becomes more like our weaker hand.
The findings were supported by a second experiment that used a gadget to record several hours of everyday hand use among 36 right-handed participants. The younger participants used their right hand far more than their left, whereas the older participants used both their hands a similar amount, despite claiming to be right-handed.
Neurophysiological studies don’t support the idea that one side of the brain ages more quickly than the other, so the researchers favour a “use-dependent plasticity” explanation for why our dominant hand loses its superiority. They said the dominance of our favoured hand is intensified through our use of it in everyday activities, so “when these activities decrease after retirement, or by the limitations in older age and sedentary lifestyles, it is conceivable that the practice-based superior performance of the right hand is no longer maintained…”.
Kalisch, T., Wilimzig, C., Kleibel, N., Tegenthoff, M. & Dinse, H.R. (2006). Age-related attenuation of dominant hand superiority. PLoS ONE, 1, 1-9. (Open access).