Well, in a sample size of 1, it doesn't make a huge amount of sense to discuss correlation -- the two facts both happened, and so have 100% correlation on that

Well, in a sample size of 1, it doesn't make a huge amount of sense to discuss correlation -- the two facts both happened, and so have 100% correlation on that sample size. (But this is a basically useless statistic for making any inferences.) The question was if we expect, given that it happened together here, we'd see it happen together more than random distribution would predict -- that is, that we see personality differences align with a split in limb control. Since they're both changes in the manner in which one interacts with the world, and my experience of the world changes in subtle ways when I, eg, use my left hand for certain tasks or sit in certain postures, I just find it unlikely that the alignment of limb control and personality are unrelated.