[jbay808]

If I were given five seconds to glance at the picture of a lion and then asked if there was anything unusual about it, I doubt I would notice that it had a fifth leg.

If I were asked to count the number of legs, I would notice right away of course, but that's mainly because it would alert me to the fact that I'm in a psychology experiment, and so the number of legs is almost certainly not the usual four. Even then, I'd still have to look twice to make sure I hadn't miscounted the first time.

[energywut]

Ok, but the computers were asked to specifically count the legs and return a number. So you've made the case that humans would specifically find this question odd, and likely increase their scrutiny. Making an error by a human even more unusual.