Bigger brain size matters for intellectual ability

[Nadvojvoda Janez Kranjski]

Public release date: 22-Dec-2005

Bigger brain size matters for intellectual ability

Brain size matters for intellectual ability and bigger is better, McMaster University researchers have found.

The study, led by neuroscientist Sandra Witelson, a professor in the Michael G. DeGroote School of Medicine, and published in the December issue of the journal Brain, has provided some of the clearest evidence on the underlying basis of differences in intelligence.

The study involved testing of intelligence in 100 neurologically normal, terminally ill volunteers, who agreed that their brains be measured after death.

It found bigger is better, but there are differences between women and men.

In women, verbal intelligence was clearly correlated with brain size, accounting for 36 percent of the verbal IQ score. In men, this was true for right-handers only, indicating that brain asymmetry is a factor in men.

Spatial intelligence was also correlated with brain size in women, but less strongly. In men, spatial ability was not related to overall brain size. These results suggest that women may use verbal strategies in spatial thinking, but that in men, verbal and spatial thinking are more distinct.

It may be that the size or structure of the localized brain regions which underlie spatial skills in men is related to spatial intelligence, as was shown in previous research in Witelson's lab on the brain of Albert Einstein.

In a further sex difference, brain size decreased with age in men over the age span of 25 to 80 years, but age hardly affected brain size in women. It is not known what protective factors, which could be genetic, hormonal or environmental, operate in women.

It remains to be determined what the contribution of nature and nurture are to this cerebral size relationship with intelligence, Witelson said. She added that the results point to the need for responsibility in considering the likely future use of magnetic imaging (or MRIs) of brain structure as a measure of ability in student and workforce settings.

"We're going to need to be careful if, in the future, we use MRI brain scans as a measure of ability in any selection process," she said.

http://www.eurekalert.org/pub_releas...-bbs122205.php

[Exeter]

I would like to hear what Agrippa has to say on progressiveness in regard to brain size and its correlation with intellectual ability.

[Nadvojvoda Janez Kranjski]

The correlation between brain size and IQ is 0.33 - 0.44 (0.4 acc. to Jensen). Bigger brain = more progressive.

Some interesting stuff:

MRI - Measured Cerebral Areas and IQ
The total cerebral area was found to be highly correlated with IQ for the total sample
(r = 0.40, t = 4.5, p < 0.001). Nearly the same correlation was also found for the anterior
cerebral area (r = 0.38, t = 4.1, p < 0.001). There was, however, not a significant
relationship between IQ and the posterior cerebral area in the same subjects (r = 0.16, t =
1.6, p > 0.05). These results were not largely influenced by the adjustment of the cerebral
areas for weight and height.

MRI - Measured Cerebral Areas and Cranial Capacities
The measured MRI areas were found to be related to cranial capacities evaluated by
skull measurements (length, breadth, and height). There were significant correlations
between the cerebral areas and cranial capacities for the total samples (total cerebral
area: r = 0.72, t = 10.6, df = 101, p < 0.001; anterior cerebral area: r = 0.59, t = 7.3,
df = 101, p < 0.001; posterior cerebral area: r = 0.55, t = 6.7, df = 101, p < 0.001).
There were no sex-related differences in these relationships.

The paper: http://cogprints.org/1369/00/IQTAN2.pdf

[Agrippa]

Obviously there are always two important things about the brain and mental abilities (not just intelligence):
A) structure
B) size

Structure is always more important me thinks though - if comparing a similar-same structure - size is the crucial difference obviously.

Considering the male-female comparison, I would suggest that in women all mental processes are usually more or less interconnected. Emotional elements and intellectual ones can harder be separated than in males, as one element of intelligence can harder become disconnected from others. In males the dominance of certain parts in certain situations seems to be stronger - which explains there stronger schizothyme and "thinking" tendencies.

This leads to the problem of women acting fully rational and without strong emotions but at the same time it gives them a general approach for everything whereas males might react in one situation very rational but on the next occasion extremely affective. So their reactions might be more extreme and finally more prone to overreactions and unadapted behaviour - again something which we can obviously see more often in males.

So in daily life males should be more rational, women more emotional, but in extreme situations males become more driven by strong affective reactions and one sided concentrations. Its thats true, it could be easily explained by the different social roles and demands for males and females.
Women should act in daily situations emotional and more caring, less (directly) aggressive and rational even, whereas males should be dominated by their ratio in daily life, whereas in extreme situations extreme affective "explosions" to mobilise all energies are more useful in males.