Making Sense of People - Samuel Barondes

"When it comes to the origins of personality, we have learned a lot. We now know that personality traits are greatly influenced by the interactions between the set of gene variants that we happen to have been born with and the social environment we happen to grow up in. The gene variants that a person inherits favour certain behavioural tendencies, such as assertiveness or cautiousness, while their environmental circumstances influence the forms these innate behavioural tendencies take. The ongoing dialogue between the person's genome and environment gradually establishes the enduring ways of thinking and feeling that are the building blocks of personality.

This developmental process unfolds, in part, through progressive changes in brain circuits, something largely completed during critical periods - windows of time that allow environmental and genetic processes to work together to build stable neuronal connections. For example, many aspects of language development take place during a window that remains open until around puberty. The difficulty in overcoming an accent in later life is a sign of the reduced brain plasticity that follows as this window is progressively closed.

On the other hand, certain programmed changes come online later in life, such as those that begin in adolescence and give rise to changes in personality and brain structure. Although it will be difficult to unravel the contributions that specific genes and events play in the decades-long process of constructing a brain and a personality, the general principles are now established.

We have also learned a lot about the second big question: how to describe personality differences. We now think of every personality as a unique blend of components. To use these discoveries to assess a specific person, it is useful to organise what we know about them into four sets of components: dispositional traits, troublesome patterns, character strengths and sense of identity. Bringing these together is, I find, the best way to build a descriptive picture of someone's personality.

The first set of components, the dispositional traits, are ones that we intuitively pay attention to in sizing someone up - and they make a useful rough initial profile. For example, when we meet someone new we intuitively ask ourselves, are they assertive or reserved? Warm or cold? Organised or disorganised? Tense or relaxed? Open to new ideas or closed? Psychologists call these traits the Big Five, labelling them: extraversion/introversion; agreeableness/antagonism; conscientiousness/disinhibition; neuroticism/emotional stability; and openness to experience/closedness."

- Making Sense of People: Decoding the mysteries of personality by Samuel Barondes (via here)