Concerning the question of why the relative brain sizes of smaller organisms are larger:
Doesn't it seem obvious that this is due to the entirely different nature of the nervous system and its function compared to other tissues? For example, a salivary gland will work the same whether it has 10,000 or 20,000 cells, appropriate to two species of fruit flies, one twice the size of the other. But given that neurons have a lower limit in size (as the article points out), one cannot halve the number of neurons and achieve the same behavioral complexity. And a fly half the size needs roughly the same behavioral reportoire, since it must react to threats, find food and mates, etc. pretty much the same.
posted by Bruce Blackwell
May 21, 2012
About once a month at Sigma Xi headquarters, we liven up the lunch hour with an American Scientist Pizza Lunch talk. In these informal lectures, scientists describe new research to nonscientists. The series is light on jargon but heavy on solid science. Each Pizza Lunch offers an in-depth look at its subject, whether it's bedbugs or the smart grid. Click below to read about and download these talks -- and to subscribe!
JSTOR, the online academic archive, now contains complete back issues of American Scientist from its inception in 1913 (as Sigma Xi Quarterly) through 2005.
The table of contents for each issue is freely available to all users; those with institutional access can read each complete issue.
View the full collection here.