On page 3, what does the difference between the way Lennie and George drink the water from the green pool reveal about their characters and situation?

As they walk along, Lennie comes upon a pool of water and drinks thirstily; George warns him that the water might be bad as it has been stagnant in the sun, but Lennie pays him no heed. Lennie is described as drinking from the pool “like a horse” (3). George is cautious, whereas, Lennie simply acts from impulse.