According to a study conducted by Daniel Horschler, a UA anthropology doctoral student and member of the UA’s Arizona Canine Cognition Center, dogs with bigger brains can perform certain tasks better than dogs with smaller brains. The researchers found that larger-brained breeds had better short-term memory and self-control than smaller dogs, regardless of the extent of training the dogs had received.
The tests showed that brain size did not determine a dog’s performance on tests of social intelligence such as being able to follow where a person points or with the dog’s inferential and physical reasoning ability.
What the study did not define is what is considered small and what is considered large? What the study also did not seem to take into account is the difference between the way humans relate, handle and treat small vs large dogs. As a canine behavior consultant and dog trainer I have seen a vast difference between the way owners treat and relate to large vs small dogs. For example, you do not see owners carrying their Labrador Retrievers around in backpacks or pushing them in strollers. Often small dogs are not allowed to act like dogs whereas large dogs are allowed to act like a dog should act. It is interesting to consider.