physiologists have long noted the correlation between brain size and intelligence in animals. Chimps, apes, humans..as one example...Dolphins, and whales...as another...the bigger the brain, the more intelligence is displayed.
Then there's dogs...all breeds do the same basic things...yet a Great Dane has a brain 20x the size of, say a Yorkie...so why isn't there a far greater capacity for intelligent behavior in the larger breeds. What do they do with all those extra brain cells?
They convince people to provide them with an enormous amount of food and an entire couch of their very own for the rest of their lives?
They store excess drool.