It's simply scientific fact that being part cat makes you like balls of yarn. Although, I'm not sure it's a good idea to let real cats play with balls of yarn. It seems like you're just asking for trouble and tangled messes.EDIT
I've been informed of a potentially fatal danger of cats eating the yarn, so DEFINITELY DON'T LET REAL CATS PLAY WITH YARN.
This realization of Tedd's regarding this sort of placebo effect was evidently made a while ago if ramblings from previous comics
are any indication. He makes no direct mention of it, but enchantment resistance is relevant and something he'd be hard pressed to study without knowing that expectations impacted durations.