In this strange article they are trying to get at the size limit for human brains, assuming brains were cooled like computer chips. Human brains are about 1.5 kg while the study points out that the thermal limits for mammalian brains (cooled like computer chips) are about 5 kg. They then point out that sperm whales have brains in the 9 kg range. Great, another thing to envy about sperm whales.
I guess the real take away is that mammalian brains are not cooled like computer chips. That explains the lack of ungainly heat sinks sticking out of our skulls. Probably a good thing, although it could make for a more interesting hat industry.