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Smithsonian National Zoological Park l Friends of the National Zoo

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The brain is the body's control center. This mass of nerve cells, and the electrical impulses they generate, allow us to walk and talk, to reason and remember, and to dream. The brain influences and monitor every activity including: breathing, balance, body temperature, heartbeat, movement, sensing and perceiving the environment, motivation, emotion, and dreaming.

The perception that brain size is related to an animal's "smartness" is dealt with in the "Brains" area of the Think Tank exhibit. In this area, there is a display of preserved and wax-cast brains, a computer interactive program on brain size, touchable bronze casts of brains, and panels on the concept of relative brain size and anatomy.

The casts show that, in general, bigger animals have bigger brains. It is not surprising since bigger "machines" need bigger "control centers." But that doesn't necessarily mean that bigger animals are better thinkers. To account for the overall size of an animal, brain weight is compared to body weight to give relative brain size. For example, when relative brain size is used, it shows that squirrels actually have a larger brain than humans. Since we know that squirrels are not better thinkers than humans, we find that brain size is not the best indication of which animals are better thinkers. Instead, the structure of the brain and the density of the neurons are probably more closely related to thinking ability than size.

The bronze casts of brains in the Think Tank exhibit were created from real brains. The brain collection of preserved and wax-cast brains is a portion of the collection of Dr. George Crile, a pioneer goiter surgeon. He started the collection in the 1930s and collected brains over several decades. Much of the research on comparative brain sizes has been based on this collection. The brain weights given for each specimen are based on real, wet brains. The collection shows visitors both the many different forms brains may take and the fact that all brains have similar components.

The computer program in "Brains" touches on a number of subjects related to brain size. Visitors are invited to guess the relative brain sizes of a human and an elephant, and to do a taxonomic comparison of relative brain sizes for a similarly-sized fish, reptile, hypothetical dinosaur, bird, primate, and non-primate mammal. The computer program also explores how characteristics of the lifestyle of mammals, such as life span, and period of maturity, prominence of sense organs, diet, home range, and social structure, affect relative brain size.