Intelligence poorly related to brain size

LONDON, Nov. 25 (UPI) -- British scientists say they've found brain size is much less related to the complexity of an organism's thought and behavior than is currently assumed.

Professor Lars Chittka of the Queen Mary's Research Center for Psychology at the University of London and Jeremy Niven of the University of Cambridge examined the brain size of a broad range of organisms, ranging from insects to vertebrates. They also analyzed the complexity of behaviors, social structures and mental processes of the organisms.

The scientists said they concluded animals with bigger brains are not necessarily more intelligent.

Chittka and Niven said a honeybee's brain weighs only one milligram and contains fewer than 1 million nerve cells, while a human brain weighs more than 1.25 kilograms (about 2.75 pounds), and contains an estimated 85 billion nerve cells. Yet the honeybee can count, categorize objects, understand the meaning of "same" and "different," and differentiate among shapes.

The researchers said the determined larger animals have larger brains partly because they need larger nerve cells. Moreover, they said larger brains have a greater number of redundant nerve circuits that add precision to sensory processes and detail to perception.

Their findings appear in the journal Current Biology.