New models outline the relationship between personality – genes – behaviour

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Do you value courage and bravery or intelligence and learning?

Your answer may indicate whether you end up in Gryffindor or Ravenclaw, according to a Harry Potter-themed personality test.

Other tests purport to tell you which breed of dog your personality most resembles; are you a protective chow chow or a calm and comforting greyhound?

Myriad personality tests, both tongue-in-cheek and serious, including the popular Myers-Briggs test that evaluates traits like introversion versus extroversion, group us into personality types.

But what is actually differentabout us?

In a new paper, titled “Personality beyond taxonomy,” published in the journal Nature Human Behaviour, Caltech researchers from the disciplines of neuroscience, psychology, and philosophy discuss the long-standing question: What is personality?

Whereas most studies measure personality in various ways, they are often ambiguous about what personality really is: Is it in the behaviors themselves or, perhaps, in the genes, the brain, or all of these?

The Caltech researchers argue for the importance of models that make such distinctions and conclude that personality resides in the brain.

“In personality research, there is considerable confusion, even among scientists, about whether personality is in the brain. You can find all sorts of descriptions of what makes up personality, ranging from genetics, through features of the brain, to behavior, but in many cases it remains ambiguous whether the quantities are causes of personality, effects of personality, or whether they actually constitute personality,” says study co-author Frederick Eberhardt, professor of philosophy at Caltech and an affiliated faculty member of the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech.

“We believe that genes and environment are causes of personality and that behavior results from personality, but personality itself is located in the brain.”

In the new theoretical study, the researchers propose specific models outlining the relationship between personality, genes, and behaviors, and propose ways of testing those models using the tools of neuroscience. They also propose ways to test the question of where in the brain personality might lie and, in particular, how personality is related to other psychological functions, such as emotion and memory.

“By laying out testable hypotheses about how personality is realized in the brain, we hope to connect these separate endeavors of studying personality in psychology with the research in neuroscience,” says Ralph Adolphs (PhD ’93), Caltech’s Bren Professor of Psychology, Neuroscience, and Biology; director of the Caltech Brain Imaging Center; and an affiliated faculty member of the Tianqiao and Chrissy Chen Institute for Neuroscience.

The Nature Human Behaviour study was funded by the National Science Foundation. Other authors of the study include lead author Julien Dubois (PhD ’13), a visitor in neuroscience at Caltech; and Lynn K. Paul, a senior research scientist specializing in cognitive and social neuroscience and neuropsychology.


Genetic studies of human personality
Personality traits are the relatively enduring patterns of thoughts, feelings, and behaviors that reflect the tendency to respond in certain ways under certain circumstances (Roberts 2009 p 140). Strong phenotypic correlations have been reported over the years between personality traits and a wide array of psychopathological conditions (Khan et al. 2005); however, it is unknown whether these correlations have a genetic or environmental basis.

Personality traits can be closely aligned with domains within the Research Domain Criteria (RDoC), which views psychiatric disorders as extremes of normal tendencies, and is intended to foster a biological analysis of behavior. While numerous genetic studies have examined psychiatric diseases, relatively less work has been done on the genetic basis of RDoC traits such as personality.

Twin studies have demonstrated that personality traits, as measured by self-report questionnaires (Cervone and Pervin 2009), are moderately heritable (Kandler et al. 2017; Bratko et al. 2017) and have a relatively stable trajectory over time after early adulthood (Kupper et al. 2011). However, the exact genetic basis of personality is still poorly understood.

We review findings from twin and family studies of heritability, followed by linkage studies, candidate gene association studies, and GWAS. We summarize the most robust loci associated with personality. We only included genetic studies of personality if they used validated, standardized, self-report measures of personality traits (Box 1) in healthy adults of any ethnic origin. We conclude by discussing polygenic methods, which provide mounting evidence that the association between personality traits and psychopathology has a genetic basis. Future directions for research are also suggested.

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BOX 1.

SELF-REPORTED QUESTIONNAIRES TO CAPTURE THE MULTIFACETED TRAITS OF PERSONALITY

The Eysenck Personality Questionnaire (EPQ; Eysenck and Eysenck 1975) defines three traits of personality: psychoticism (characterized by aggressiveness and interpersonal hostility), extraversion (manifested in outgoing, energetic behavior), neuroticism (typified by emotional stability).

The Tridimensional Personality Questionnaire (TPQ; Cloninger, 1986; Cloninger, Przybeck, & Svrakic, 1991) consists of three traits of personality (or temperaments) that are based on the biochemical bases of temperament: novelty seeking (or the intense exploration towards novel stimulation or potentially rewarding cues, and active avoidance of punishment), harm avoidance (or the tendency to respond intensely to aversive cues, and to learn to avoid punishment and novelty), reward dependence (or the rapid response to rewarding cues and/or relief of punishment).

Later, the Temperament and Character Inventory (TCI; Cloninger et al. 1993; Cloninger 1994) included a fourth temperament dimension, persistence (or perseverance in spite of fatigue or frustration), and three character traits – self-directedness (the ability to modify behavior in order to achieve personal goals), cooperativeness (the tendency to exhibit agreeable relations with others) and self-transcendence (associated with experiencing spiritual aspects of the self).

The Five Factor model (Costa and McCrae 1992) is based on biological mechanisms shaping five higher-order traits (referred to as ‘the Big Five’ personality traits): neuroticism (proneness to experience negative affect), extraversion (motivation to engage with others), openness to experience (inventive or curious behavior), agreeableness (friendliness and compassion toward others), and conscientiousness (attentive and organized behavior). The NEO-PI questionnaire (NEO; and its derivatives, such as the NEO-PI-R and NEO-FFI) is the most commonly used questionnaire for genetic studies.

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Developments in the field, including the availability of large datasets such as UK Biobank, and bioinformatics techniques such as gene pathway analysis, have furthered our understanding of the genetic etiology of personality. Ultimately, genetic studies of personality may enhance our understanding of neuropsychiatric diseases and thus foster novel treatment approaches (So et al. 2017).

reference link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7012279/


Original Research: The study will appear in Nature Human Nature

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