We have 3 animals in the house: a dog and 2 cats. So we have 3 water bowls for them which we line up in a row against the wall in the kitchen. The bowls are all the same size and material and roughly the same shape. Always, without fail, the bowl that is farthest to the left gets emptied first, followed by the one in the middle, and then the farthest right. We've switched them around and it makes no difference. The pets always drink left to right.
I can see no logical explanation for this.
The end.