[...] to complete a four-piece puzzle representing a horse (their measure of 'spatial ability')

I see at least two obvious confounding variables that can wildly influence this measure. (And I'm not saying I have any better measures to suggest.) The first question is whether fast hand movements are considered appropriate in the given society. If the norm for your gender is gentle, majestic movement, that slows you down. The second question is what your society's gender norms are for deliberateness/decisiveness.