Pet owners have long argued whether dogs or cats are the smarter species. A common argument is that dogs have larger brains than cats, though brain size doesn't necessarily reflect intellect -- likewise, a big German shepherd isn't necessarily smarter than a tiny Chihuahua. Research shows that thousands of years of canine and human cohabitation have influenced brain growth, but how has brain growth influenced dogs' capacity for learning from their human counterparts?
Socialization Fosters an Increase in Brain Size
Current and recent scientific research shows a defined pattern in evolutionary brain growth in mammals: animals that are more prone to socialization (such as dogs, horses and dolphins) develop larger brains than more solitary species (such as cats and deer). These findings prove that regular interaction with other animals (including humans) will result in a larger brain size, which is why dogs' brains are so much bigger than other, less social species'.
What Does Socialization Mean for Learning Capability?
A more highly socialized species of animal will inevitably be more responsive to learning non-instinctual lifestyle behaviors or being trained, which can imply that a larger brain signifies a larger capacity for learning. However, it can also be argued that dogs' brains have grown larger to support the species' increased capacity for learning. It is a veritable "chicken and the egg" mystery of science and evolution.
Canine Domestication Creates Evolutionary Puzzle Pieces
Research states that canine domestication produced a 10 percent brain size reduction in both dogs and humans. The significance in this reduction is that different sections of the brain shrunk in each species. Temple Grandin, a noted doctor of animal science, has a theory as to why: "Dog brains and human brains specialized: humans took over the planning and organizing tasks, and dogs took over the sensory tasks." This implies that canine brain size directly correlates to cohabitation with humans. Without having to learn the skills for which they relied upon humans, their brains did not need to be as large.
The Canine Brain in Training
In a recent study, researchers trained dogs to sit for brain scans. When signaled that they would receive a treat, the sector of the dogs' brains that responded was the same sector in humans that signifies a reaction to a reward. This provides further evidence that dogs' brains have been co-evolving with humans', and focusing on the similarities between the two species' brain functions (as opposed to only considering size) provides insight into how we communicate with our canine companions, and thus how we are capable of teaching and training them.