Why do some people have below-average IQ?


In seeking to understand variations in human intelligence, we should explore scientific findings pointing to the biological roots of Intelligence Quotient (IQ). This intriguing landscape reveals that various brain characteristics, from genetic polymorphisms to structural organization, contribute to disparities in IQ. Smaller brains marked by inefficient neural arrangements are associated with lower IQ. Brain dimensions, as well as neurite organization, emerge as crucial factors.

Cortical thickness and surface area prove to be key indicators. The positive correlation between cortical thickness and IQ underscores the importance of this region. Surface area, in turn, represents the number of cortical columns, directly influencing intelligence. Connectivity, measured by core connections and average path length, plays a vital role. More efficient networks contribute to higher IQ.

Lower levels of myelin, responsible for signal speed, are associated with lower IQ. Additionally, efficiency in glucose consumption during cognitive tasks stands out as an intelligence indicator. Efficiency in communication between brain hemispheres, influenced by the size, shape, and curvature of the corpus callosum, plays a significant role. Glial cell density, once considered only as cerebral "glue," emerges as a critical factor, with low density associated with lower IQ.

Genetic factors contribute to substance production, with efficiency necessary for higher intelligence linked to the allele effect. Also related to genetics, factors such as breastfeeding and natural childbirth contribute to increased intelligence. In neurodevelopment, healthy habits and reduced screen time have a strong effect on intelligence development using related genes as precursors.

Healthy pregnancy, traumatic factors from birth, also influence intelligence development. Substance consumption, alcohol, cigarettes, certain medications, stress, a family environment lacking necessary resources for pregnancy neurodevelopment, as well as violence, abuse, traumas suffered from birth, impact intelligence.

This detailed mapping provides a deeper understanding of the complexities contributing to IQ variation. By unraveling these connections, we create room for a more comprehensive appreciation of why some people face specific challenges in their intellectual journey.

By Dr. Fabiano de Abreu Agrela Rodrigues

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