A new study challenges previous assumptions about the correlation between brain size and intelligence in dogs. The research reveals that working dog breeds possess the smallest brains relative to their body size, yet they likely possess more developed intellectual abilities. On the other hand, dog breeds with larger relative brain size tend to show higher levels of fear, aggression, attention-seeking behaviors, and separation anxiety. The study suggests that excessive breeding of dog breeds by humans has led to changes in the natural structure of dogs' brains. The researchers also noted that variation in the shape of the neocortex across dog breeds could shed light on the senses and functions that are important for different types of dogs.