Can you have too much intelligence? Using individuals of the same species as comparisons is essential for this method to provide accurate results. The impact of brain size on intelligence is negligible even in this context; other characteristics are much more important.
It has been speculated for ages that a person’s IQ may be inferred from their brain size. It makes sense on an intuitive level that a larger brain would have more room to process and store information. Do I have it right?
A look at how vertebrate brains compare reveals that things are more complex. Most other whale species have smaller brains compared to the sperm whale. The marine animal has a relatively small brain compared to the rest of its massive body. Perhaps the ratio of brain to body weight is more important. The shrew would thereafter be recognized as the vertebrate with the greatest brain. Scientists used to find correlations between any two measurable aspects of the body or brain. Humans, however, did not place top in any of these neurocharts, which was a major surprise.
Animal species differ widely in their intellect and behavioral versatility, and this can’t be inferred from their (relative) brain sizes alone. The size and concentration of nerve cells varies greatly across species, which is a major factor in this. The neurons in human brains, for instance, are packed more densely and need less space than those in the brains of many other animals.
Could there be a correlation between brain size and behavior amongst different species? An ancient tale about Friedrich Schiller’s graveyard demonstrates how reasonable this presumption is. Goethe had already requested that his poet buddy Schiller be buried close to him at the Weimar Princely Crypt. However, the latter had passed away at a young age, and his burial location in the “cash vault” remained a mystery. After comparing many sets of bones to Schiller’s death mask without success, the biggest skull was selected to be interred beside Goethe. It is said that the ethereal being need a great deal of quiet in which to contemplate his world. However, the theory of the astute huge skull is not completely erroneous, as DNA investigations conducted in the 2000s have shown. Research on the correlation between head size and intelligence began in the early 20th century. Early measurements were relatively inaccurate, but the vast bulk of this study pointed to a favorable correlation. However, since the advent of sophisticated imaging techniques like magnetic resonance imaging (MRI) in the 1970s, it has become possible to precisely quantify brain volume in healthy, living individuals. Researchers look at absolute volume instead of body size when doing intraspecific comparisons. Such approaches have indicated that variations in brain size account for a significant portion of the variance in IQ.
A variation in brain size has been demonstrated to account for as much as one standard deviation of IQ difference between individuals, according to certain research. To have an influence of such magnitude would be really remarkable. Many more studies have been published since then, all of which have come to the same conclusions: larger brains tend to be more intelligent, and vice versa. However, this only accounts for a marginal portion of the variance in IQ scores (about one in twenty), thus it should be taken with a grain of salt.
This suggests that there are numerous factors outside brain size that contribute to our cognitive ability, and that the size of the thinking organ should not be considered the primary determinant of intelligence. Greater importance to intelligence is owed to the quality of the neural circuitry and the level of interregional communication in the brain than to brain volume per se. The more efficiently your brain’s gray matter is connected, so the saying goes.