Are your brains BIG?


I just found out that the students of cogsci (here in Helsinki) are arguing passionately (greetings to Ilmari + guys) about this story:

So, does the size of brains matter/correlate with the IQ… This may be a complicated question, and I was just thinking what the situation with the current comparative study is right now. For instance, it is at least possible that there are brains that are smaller, but which are cytoarchitectonically more “efficient” than the larger brains, right? But is there any hard empirical evidence?



  1. gualtiero

    In the 19th Century there were many people assuming that brain size correlates with intelligence and doing pseudo-science based on it. SJ Gould wrote a chapter about it in his The Mismeasure of Man. I don’t know about recent evidence, though.

  2. Studying such correlations seems to me like a complete waste of time. I am sure lifestyle, childhood nutrition and stimulation, education, and so on, are much more important factors than the size of one’s brain (let alone head). Also, if there is any interesting correlation between size of brain and intelligence, then why does the body mass/brain size ratio matter? Is the idea that a big brain on a big body uses more of its energy tending to the body?

  3. Carl

    Hi, there is lots of good evidence across species that brain size does not track intelligence.

    For humans here is a blunt way of seeing it likely may not matter too much either, and by the way I think it is a pretty interesting fact in itself.

    The cases I am thinking of are juvenile hemispherectomies — ie the removal of one of the brains hemispeheres at a young age. This is now the preferred treatment of Rassmussen’s syndrome, which is a nasty, very debilitating form of epilepsy.

    Anyway, there are hundreds of people who have now had these hemisphere removals over the last few decades. These folks obviously have VERY small brains, half the size of yours! But many of these subjects only suffer some visual and motor loss on the side relevant to the hemispehre they lose. However, their intelligence levels allow them to go through college and be otherwise indistinguishable in cognitive, rather than motor, skills from normal subjects.

    So, the brain has the capacity to rewire itself to achieve many of the same cognitive ends across roughly half the material. Would such plasticity mean that volume, at least in the cortex? It looks like it might.

    Best, Carl

  4. Recently, we are witnessing a ressurection of the old phrenology in the neurological sicences. That pseudoscience of the 19th century championed by Gall and his discipule Spurzheim, suggesting that certain cerebroneural circuits are associated in a biderectional fashion with some current behavioral functions ranging form sexual libido, virtues, patience and even lust. In current terminology the modular view (e.g. Fodor) in cognitve science, is in some sense something like a prhenological revival but with more sicentific evidence.
    I don´t remember actually but forensic neurologists in the states have been collecting the dead brains of thousands of individuals finding a clear correlation with the size of the fibers pathways and the corpus callusum with inteligence (or as it is the case in the score of intelligence tests) and anecdotically they have postmortem conclusions and data of the brains of certain geniuses, such as Einstein, and the facts probes their thesis; so size in this case really matters!

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