Personally, I would expect a starving person to perform significantly worse on a math test than a non-starving person. Heck, I would expect a very hungry person to perform significantly worse on a math test than a non-very-hungry person. I've been hungry during the course of today and I think my mental performance was worse when I was hungry. When I'm hungry, it feels like my brain has an aversion to thinking hard, presumably in order to get me to preserve energy.