Chimps have been found to be able to distinguish between different quantities of liquids under a number of different methods. This includes a simple choice, to figuring out quantities based on pour length (even at varying heights), and judging if a pour represents more then what they can see in a separate container.
"Chimpanzees are intelligent enough to appreciate how big a pint of liquid is, or the volume of any other measure.
That shows they have an ability to gauge the difference between continuous quantities, such as a pint or half pint of non-alcoholic fruit juice.
Previously, apes have only been known to differentiate discrete quantities, such as eight sweets over five.
That means chimps are more intelligent than we thought, and shows they have a basic grasp of the physics of liquids."