I've tried to catch him out like that with a couple of variation, and he always sticks with the bowl with most scoops. I'll put a single scoop in his bowl -- which he starts to eat straight away -- then three scoops in the other bowl, then a final scoop in his. He stays with the other bowl, which has had one extra scoop of food, even though his own bowl has had the most recent scoop added to it.
If I put two scoops into his bowl, and two into the other, he stays with his bowl. He only switches when a third scoop goes into the other bowl. He's been consistent with this since I noticed him doing it, and I'm not sure how long before I noticed he was doing it that he started doing it.
One way to test this would be to use a scoop that's 2x bigger than the other scoop, and putting in 3 scoops using the smaller scoop vs. 2 scoops of the bigger scoop.
Tried that by using three half-ish full scoops against two full scoops. He always goes to the bowl which has had the highest number of scoops in it, even though it might actually have a lower quantity of food in it. He seems to be counting rather than comparing quantity, because his trigger is the other bowl getting +1 scoop versus his.
Can we measure when he loses count by using many small scoops? I expect if his current bowl has passed a certain threshold of scoops he won't bother switching no matter how many scoops are going there.
If I put two scoops into his bowl, and two into the other, he stays with his bowl. He only switches when a third scoop goes into the other bowl. He's been consistent with this since I noticed him doing it, and I'm not sure how long before I noticed he was doing it that he started doing it.