Heritability and consistency of personality

Once we know what we are testing and the means by which it can be measured, we can compare results between groups and over time. This is important for a number of reasons, most notably because it means that we can assess the heritability of traits. The term heritability is an awkward one and the subject of much confusion. Geneticist Adam Rutherford has described heritability as both a 'tricky idea' and a 'hideously named thing' (Rutherford, 2016 p. 305) mainly because it sounds a little like inherited and this leads to untold confusion. Heritability is a measure of how much of the difference we see in a population can be accounted for by genetics and how much is determined by the environment. It isn't just about genes, nor is it just about the environment; it is about populations but not about individuals. Not only does this allow us to examine the possible heritability of personality traits, it also allows us to test an important premise - that traits remain stable over time.

This stability is particularly important. Trait theory indicates that our personality won't alter too much over the years, so the behaviour we see in an eight-year-old should still be present at 80. That said, there is a period of stability, in that traits appear to become more stable across the lifespan. Does the conscientious 15-year-old, for example, become a conscientious 30-year- old? We can see a similar pattern with intelligence, in that measures of IQ can be pretty unstable in early and mid-childhood but tend to settle during late teens and early twenties.

There does certainly appear to be a high degree of stability with personality traits; it does increase with age and levels off at around the age of 30, it then stabilises further between the ages of 50 and 70. Some traits, however, are more or less stable than others. So, yes, the conscientious 15-year-old should still be conscientious at 80, at least according to trait theory. However, recent research by Matthew Harris and colleagues at the University of Edinburgh and Liverpool John Moores University casts doubt on this (Harris, Brett, Johnson & Deary, 2016). Harris and his co-researchers found little consistency of traits in a groups of 174 participants whose personality was measured at the age of 14 and then again at the age of 77. This seems like a pretty damning indictment of the main premise of trait theory (that personality remains stable over time). But, as some have pointed out, the longitudinal nature of the study turns out to be a double-edged sword. While, on the one hand, Harris' study is the longest in the history of personality research, much has changed and we now understand a great deal more about personality, not least of all, the Big 5 model has become the standard means by which to identify traits. There is also the possibility that trait facets are changing or people are leaning towards one aspect of the trait and not the other. I'll look at this in more detail when I discuss individual traits later.

There certainly is evidence indicating that we do change as we age. People become more conservative in their views and less agreeable, yet these changes are rather slight and happen gradually. A meta-analysis published in 2017 by Eileen Graham and her colleagues, for example, found that people become less agreeable and more introverted with age. However, some traits change more than others and the extent to which people's personality changes throughout the lifespan is yet to be fully understood.

Temperament or character?

It was noted briefly in Chapter 2 that personality traits are not the same as character traits, and that the former are innate while the latter are learned. Here we make the distinction between temperament and character, where by temperament we refer to what we generally consider to be personality traits. Temperament is embedded within our biology and is heritable, that is, across populations there is a strong tendency for closely related individuals to measure similarly. These would include Big 5 traits such as openness and extraversion. This isn't to say that the environment has no influence on traits, only that they appear to represent a highly biological component that interacts with environmental factors. Character traits are different because they are not qualities that we are born with or ones that develop shortly after birth. Character traits are learned through interactions with the environment, primarily through familial influence, but also through other significant people such as close friends and teachers. The distinction can appear quite woolly, but we can tentatively claim that traits such as extaversion have a biological basis while kindness and compassion are learned from the people around us. Teaching (or nurturing) character traits then becomes both a worthy and legitimate endeavour, while teaching an introvert to be an extravert is highly problematic and most likely to end in failure. Character traits are also often learned vicariously, that is, through observation of others acting is a particular way and being rewarded for it. Young children, for example, might notice that their friends and classmates are being praised for their politeness or empathy towards other people; these behaviours then form blueprints in long-term memory (scripts or schemas) of the most appropriate way to behave in specific situations. Praise then reinforces this behaviour.

Our character traits are certainly more malleable than those related to our temperament, but a deeper discussion of these distinctions would perhaps only serve to muddy the waters. We can encourage and nurture attributes such as honesty, compassion and respect for our fellow human beings but other less appropriate behaviours such as bigotry, misogamy and intolerance (and countless other behaviours besides) are learned or the result of social psychological factors including obedience and compliance. If these can be learned, then it follows that more positive ones can also. So where does this leave the likes of resilience generally and academic buoyancy specifically? As discussed in Chapter 2, resilience does display trait-like qualities. The original version of academic buoyancy includes a number of important attributes (the 5Cs), some of which could be described as temperaments (that is, personality traits) while others appear more similar to character traits. This chapter is concerned with those attributes that, at first sight, are more trait-like. Just as a means of clarification and to avoid confusion, note that when I use the term traits, I am referring to those included within the Big 5 model, although I may refer to other personality models for reasons of comparison. I will also use the term character traits when the need arises to distinguish them from personality traits.

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