The animal said to have the largest brain relative to its body size is the ant. Ants have a remarkably high ratio of brain size to body size compared to many other animals. The complexity of their social structures and behaviors requires advanced cognitive functions, which is reflected in their brain architecture. Ants exhibit sophisticated behavior, including foraging, communication, and teamwork, which are all driven by their relatively large brains when compared to their small overall size. This highlights the efficiency of their nervous systems, allowing them to perform complex tasks and adapt to diverse environments.