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Compare Brain and Body Sizes

What is the relationship between brain and body size?


Evaluation of brain and body size is important in studies about intelligence. When comparing animals and their levels of intelligence, one method is to look at respective brain sizes.

On the next couple of pages will be a series of tables designed to help us visualize brain and body sizes and develop questions from them. The table below shows brains approximately proportional to the size of the animal pictured in color. Mouse over each animal picture for a silhouette of its full body. Click on the pictures of the animals to read specific information about the species.



      Brain Length

      Brain Weight

      Body Length

      Body Weight

 human head


 human brain 15 cm 1,400 g 100 cm 62,000 g

 baboon head


baboon brain  8 cm 140 g 120 cm 30,000 g

 rhesus monkey head

Rhesus Monkey

rhesus monkey brain  5 cm 180 g 30 cm 6,800 g

 camel head


camel brain  15 cm 680 g 200 cm 529,000 g

 dolphin head


 dolphin brain ---- 1,700 g 300 cm 160,000 g

 kangaroo head


kangaroo brain  5 cm 56 g 150 cm 35,000 g

 cat head


cat brain  5 cm 30 g 60 cm 3,300 g

 raccoon head


 raccoon brain 5.5 cm 39 g 80 cm 4,290 g

 rabbit head


 rabbit brain 5 cm 12 g 30 cm 2,500 g

 squirrel head


 squirrel brain 3 cm 6 g 20 cm 900 g

 leopard frog head

Northern Leopard Frog

frog brain  2 cm 0.1 g 10 cm 18 g

(You can look at this chart to see the approximate values for brain/body lengths and weights used above)


Would you rather compare brains when the animal pictures are in proportion, equalize brain size, or equalize body size?


click to compare brains with animal pictures in proportion               click to equalize brain size           click to equalize body size


What?'s picture

Adult brain?

Am I missing something? Why does the comparison say that the human body is 100 cm? Every other animal body length corresponds with the correct brain weight, length, etc... I don't come across many adults that are about 3 feet tall. Additionally, the body weight of a human (per your standards) is 136 lbs, making this human example pretty much an obese midget.

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