Battle of the Brains: Size Matters
• Sexual dimorphism, or gender differences in appearance and behavior, arose because selection pressure acts differently on males and females. It is surprising, then, that brain sizes typically do not differ between the sexes in the animal world. Yet, gender differences between selection pressures are common and the brain is one of the most adaptable and plastic organs. Recently, scientists discovered a dramatic difference in brain size among stickleback fish: the male brain is nearly 25% larger than the female, for the same body size and weight amongst fish living in two habitats (mud and lava) of Lake Mývatn in Iceland (see image).
• Bigger is Better: Greater neural mass means greater information processing and superior cognitive power. In animals, larger brains have been shown to coincide with bower complexity in male bowerbirds and with single parenting by females in cichlids. Male sticklebacks build elaborate nests, perform elaborate courtship displays and care for their offspring alone. So guys, pay attention to the nursery if you want to be smarter!
• Delusions of Gender: The costly gain in brain size usually comes with compensation you know where. Male bats trade testis mass against brain mass. Female sticklebacks invest heavily in egg production, which take up 40% of their body weight. What about humans? Studies showing differences in male and female brains are highly controversial. http://goo.gl/6UVwI
Ref: Extreme Sexual Brain Size Dimorphism in Sticklebacks: A Consequence of the Cognitive Challenges of Sex and Parenting? PLoS One. 2012; doi: 10.1371/journal.pone.0030055