Are human personalities preprogrammed?

by Muhammad Adeeb Fakier

“The apple does not fall far from the tree”, is a common saying relating to offspring having a similar characteristic or quality to the parent. The advancement in genetic studies has allowed for the identification of genes associated with specific phenotypic observable characteristics, but what is the relationship between genetics and personalities?

Research from family, twin and adoption studies have indicated strong evidence for heritability of human personalities. However, the phenotypic architecture of the human personality is complex, and therefore includes uncertainty as either the same genetic networks may lead to different phenotypic outcomes; or different genetic networks in complex systems may lead to the same outcome. Past genome-wide association studies (GWAS) had very little success, where heritability of complex traits have been called “missing” or “hidden”.

The Temperament and Character Inventory (TCI) is a system that evaluates specific dimensions of personalities. TCI character traits have been identified to be associated with brain networks for metacognitive processes such as self-reflection and purposefulness; whereas temperament traits (innate traits) generate and condition automatic behaviors, such as stress reactions. Therefore focusing on self-regulatory character traits such as self-directedness, cooperativeness and self-transcendence can be used determine the health state of an individual’s adaptive functioning.

The study utilized a machine learning method for GWAS to uncover the complex genotypic-phenotypic networks and environmental interactions. A discovery sample of 2149 individuals were used, and sets of single-nucleotide polymorphisms (SNPs) that cluster within particular individuals were identified. Thereafter five cluster of individuals with distinct profiles were identified. Lastly the association significance of the SNP sets with one or more character profiles (resourceful, organized, creative, dependent and apathetic) were identified.

The GWAS analysis of the genotypic and phenotypic architecture of personality measured by the TCI, illustrated each SNP set maps to one or more genes, identifying its association to each of the five general character profiles (Figure 1). This was followed by categorizing the variation in health status of SNP sets as: well, ill and intermediate (Figure 2). It was found that 42 SNP sets identified to 727 gene loci were significantly associated with one or more of the character profiles. Interestingly the SNPs sets often had similar character profiles associated with particular molecular processes such as involved in regulation of inositol-calcium signaling for obtaining food (G_8_8) and for neuroprotection against injury (G_12_8).

In conclusion genetics have an influence on human personalities, and this study has illustrated that it is possible to characterize the complexity of genotypic and phenotypic architecture of self-regulatory character traits. The study highlighted that self-regulatory personality traits are strongly influenced by organized interactions among more than 700 genes, despite variable individual cultures and environments.

Reference

Zwir, I., Arnedo, J., Del-Val, C. et al. Uncovering the complex genetics of human character. Mol Psychiatry 25, 2295–2312 (2020). https://doi.org/10.1038/s41380-018-0263-6

Zwir, I., Mishra, P., Del-Val, C. et al. Uncovering the complex genetics of human personality: response from authors on the PGMRA Model. Mol Psychiatry 25, 2210–2213 (2020). https://doi.org/10.1038/s41380-019-0399-z

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