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Personality, Nature and Nurture

Personality tests are instruments that seek to reveal different aspects of that vague mixture of inherited characteristics (nature) and acquired attributes (nurture) we call 'I'; its application covers a wide range of purposes, such as advice on interpersonal relationships, career inclination, or employee selection. There are hundreds of types of personality tests, being the 'Big five personality traits’ model (also called the ‘five-factor’ model) the most widely recognized. Although originally proposed more than half a century ago, this approach would not consolidate as the preferred guide on the subject (though not unanimously) until the early nineties.

The model of the 'Big five personality traits’ has been validated in many scenarios (age groups, geographies, languages...) and applied in numerous investigations. Using its approach, several studies of identical twins (twins with similar DNA), raised together or apart, have confirmed the generally and intuitively accepted assertion with respect to human behavior: Nature and nurture affect our personality with similar intensity, almost fifty-fifty percentagewise.

The answers to predefined questionnaires are the basis for the calculation of the five dimensions in the model: (1) sociability (extraversion versus introversion), (2) opening to experience (haste versus caution), (3) level of responsibility (conscientiousness versus negligence), (4) interest in social harmony (friendliness versus suspicion), and (5) emotional level (stability versus 'neurosticism').

In its advanced versions, the model specifies six subordinate facets for each factor. The facets for the fifth factor, which are relevant to this note, are anxiety, hostility, tendency to depressive emotion, sensitivity to 'what people say', immoderation and stress vulnerability. In the factors and facets as measured, does the model differentiate between the effects coming from genetics and those resulting from environmental causes? Not so. It is impossible to know what fraction of anxiety, hostility or stress vulnerability is inherited or acquired.

"We are shaped by our genes in ways that none of us can directly know", says Steven Pinker. Parents’ genes mix randomly in their children (and so for generations backwards) and the combinations of the genetic roulette grow with the complexity of organisms, such complexity being highest in humans. The North American psychologist adds: “The two traditional shapers of a person, nature and nurture, must be augmented by a third one, brute chance. The environment, then, is not a stamping machine that pounds us into a shape but a cafeteria of options from which our genes and our histories incline us to choose". Our genes do not encode our addiction to alcohol or cigarette but rather the predisposition to certain vices, that we can take or ignore (though not always).

Science still lacks the methods that would allow the identification of the DNA fragments that are determinant in the presence of certain characteristics in our personality and, even less, it lacks the instruments to adjust the genes involved in this or that peculiarity.

On the other hand, this we do know, the influences of culture in our behavior are recorded in our brain as neural connections that can be modified up to a certain extent. As the Buddha never heard the words 'neurons' or 'neurotransmitters', he used the term 'formations' to refer to the mental conditionings, wholesome or harmful, that create our sense of identity. Psychotherapy commonly aims at modifying such conditionings to the positive healthy direction (reinforcing the wholesome, cutting down the harmful).

Phobias and addictions, originating from uncontrolled aversions and immoderate cravings, respectively, are harmful formations or conditionings. When our unbalanced behavior still does not require psychotherapy (or still we refuse to recognize such a need), we can influence our cravings and aversions that cause us anxiety and stress, through the practice of mindfulness meditation. This exercise enhances our faculty of attention and strengthens the brain’s inhibitory neuronal circuits that put at bay both phobias and addictions.

In summary, behavioral problems originating in the DNA (nature) still have extremely limited solution paths. Behavioral problems resulting from harmful formations (nurture), programmed in neuronal connections, on the other hand, have much higher expectations for adjustment. Moreover, the consequences of the formations are predictable and amendable on the fly. Such anticipation and such correction may save us many visits to the psychotherapist ... and a few hundred dollars.

Gustavo Estrada
Atlanta, March 20, 2015