Whole brain size and general mental ability: a review

Area of Science:

• Cognitive Neuroscience
• Behavioral Genetics
• Evolutionary Psychology

Background:

• The relationship between brain size and general mental ability (GMA) is a long-standing topic in scientific inquiry.
• Previous research has explored this association using various methodologies and populations.

Purpose of the Study:

• To systematically review and synthesize existing literature on the correlation between whole brain size and GMA.
• To investigate how this relationship varies across different measurement techniques, populations, and demographic factors.
• To examine brain size and GMA from evolutionary and behavioral genetic viewpoints.

Main Methods:

• Meta-analysis of published studies correlating brain size (measured by brain imaging or external head size) with GMA.
• Analysis of correlations across different age groups, socioeconomic positions, sexes, and ancestral populations.
• Review of studies employing the method of correlated vectors to assess the general factor of mental ability (g).

Main Results:

• A significant positive correlation between brain size and GMA was found across studies.
• Brain imaging techniques yielded a mean correlation of 0.40, while external head size measures showed a mean correlation of 0.20.
• The method of correlated vectors indicated a stronger mean correlation of 0.63 for the general factor of mental ability (g).

Conclusions:

• Whole brain size is a significant correlate of general mental ability in humans.
• The strength of this association is influenced by the methodology used for brain size assessment.
• Further research into evolutionary and genetic factors can provide deeper insights into brain-behavior relationships.