My guest post for my university’s School of Graduate Studies blog is up! (You can read it here.) The inspiration was a new radio podcast that we have in the works on research here at Queen’s – scientific and otherwise. I’ve been working on the concept with Vee, an English PhD, and Savita, an undergraduate student who is keen to make top-notch radio documentaries.
I wrote the blog post to try to drum up some interest in being a subject of the radio show, but I hope it has a few nuggets of advice for those finishing and/or considering grad school as well.
There’s no question that broadly speaking, big brains are smart. Take humans, for instance: our brains weigh in at about 3 pounds on average, nearly four times the size of the brains of chimpanzees (whose brains weigh in at less than a pound apiece).
What’s less clear is why. There are a number of theories: maybe intelligence evolved to give us a competitive edge in foraging, or maybe it helped us keep track of increasingly complex social interactions. Ideally, we’d like a theory to explain the evolution of intelligence broadly, so researchers have tried to these hypotheses across multiple species (for instance, comparing relative brain size and social group size among hoofed mammals like horses and deer1).
But brain size alone – even when scaled as a proportion of overall body size – is not an ideal measure of intelligence. The trouble is that small animals often have considerably higher brain-to-body mass ratios – ant brains, for instance, can weigh nearly 15% of their total body mass (the equivalent of a 20 pound human head!), and mice have about the same brain-to-body mass ratio as we do. So how can we study brain evolution, when even primates span a 3000-fold difference in body size (comparing a gray mouse lemur and a gorilla)?
Enter the encephalization quotient, or EQ, a measure of brain size relative to what we would predict, given that there is a curved relationship between brain size and body size (allometry is the technical term for this). It’s the best yardstick we have for the evolution of intelligence. Until now, that is.
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