That's interesting, but hardly unexpected from a cognitive perspective. Zero is even, but it's not a prototypical even number (like 2). Similarly, if you ask pe

That's interesting, but hardly unexpected from a cognitive perspective. Zero is even, but it's not a prototypical even number (like 2). Similarly, if you ask people whether an ostrich a bird, they take longer to respond than with a more typical example. A very clearly (and simply?) defined category such as even numbers is an interesting edge case of the phenomenon.