My husband has a thing for symmetry. Pictures must be hung in even numbered groupings, all level and centered, furniture in balanced and squared arrangements; artistic angles or whimsical off-centeredness make him un-easy. He knows this, but often he will find himself attracted to something without being able to identify why. He fell in love with our current house long before it went on the market and decided to purchase it almost the moment it did. He thought it was the great front porch until I pointed out that the style is one which is square and symmetrical not only side to side, but also front to back and even top to bottom.
The other night, after finally getting to play after what seemed like weeks of either travelling or hosting houseguests, he decided not to uncuff my wrists. He decided I should sleep all night this way. That was totally out of the blue, he'd never even hinted or joked about it before. The next morning I asked him why he wanted that, and why he liked it. He didn't have an answer, or at least not one he was willing to let me in on. I think that beyond whatever other reasons there may be, on some level, it's the symmetry. Part of what made it more awkward to sleep was the fact that both of my arms/hands had to move together and to maintain the same position. The arms maintaining a symmetrical posture even influences the legs and makes an asymetrical posture for them less natural. I'm pretty sure this didn't occur to him though, which leaves me really curious as to what he did like about it.