In this study they observed specific patterns that previously were attributed to learning and remembering.
> "The present findings suggest that the intricate and precisely controlled handwriting movements have a beneficial impact on the brain’s connectivity patterns related to learning and remembering."
But you are right, they do not directly _prove_ that handwriting yields a greater learning effect.
> "The present findings suggest that the intricate and precisely controlled handwriting movements have a beneficial impact on the brain’s connectivity patterns related to learning and remembering."
But you are right, they do not directly _prove_ that handwriting yields a greater learning effect.