Daniel Nettle is Reader in Psychology at the University of Newcastle. With degrees in both psychology and anthropology he has written on many aspects of human nature. In the excerpt below, from his book Personality: What makes you the way you are, we learn how one might begin to measure personality. Read other OUPblog posts about Nettle here.
“Personality is and does something…It is what lies behind specific acts and within the individual.” -Gordon Allport
It might be conventional to begin with Hippocrates, and his ideas about the four humours, or with some other ancient conception of personality types. I prefer, however, to begin our story with an article published by Sir Francis Galton in The Fortnightly Review for 1884 entitled ‘The Measurement of Character’. Galton is an apt place to begin for a number of reasons. As Charles Darwin’s first cousin, Galton was an early champion of evolution and of the view that evolution is relevant to humans. The way he could think of applying it was filtered through his Victorian preconceptions about society and societies, and so does not seem appropriate to us today. However, his basic intuition that the theory of natural selection would ultimately have to inform our thinking about everything people do has turned out to be correct.
A second reason for interest in Galton is that it was he who first realized that studies of how characteristics ran in families, and particularly studies of twins, were the key to unlocking the contribution of nature and nurture to human variation. This insight lies behind a whole scientific field, known as behaviour genetics, a field that has flourished since Galton’s time, and whose results we will meet later on.
Finally, Galton is noteworthy because he had a very modern preoccupation with measurement. Galton was obsessed with trying to find practical measures for obscure bits of human behaviour. In 1885, he published a paper in Nature entitled ‘The Measurement of Fidget’. In this he notes, from his own extensive observations, that in a large gathering such as a lecture, audience members fidget around once a minute on average. However, when the lecturer really holds their attention with a point, this rate is diminished by around a half, and moreover, the fidgeting changes. The period of the movements reduces (an enthralled audience member gets their movement over as quickly as possible, whereas a bored one draws it out), and the angle of deviation of the body from the upright…also reduces. Thus a quick index of how bored an audience is at any point in time would be on average how far from vertically upright they were. Galton commends these insights to the reader as promising to give ‘numerical expression to the amount of boredom expressed by the audience generally during the reading of any particular memoir’.
Quirky as this paper is, it is very modern. Many philosophers before Galton had speculated about human traits, but few had seen that none of this was worth the candle-scientifically at any rate-if the traits in question could not be measured. Most of the work in scientific psychology consists in trying to come up with good measures of things, and showing that they are good measures. Indeed, a concern with measurement is precisely what distinguishes ‘academically respectable’ psychology from psychology of other kinds. Galton measured the weights of livestock and aristocrats, the speeds of reaction times, the sizes of heads, the shapes of fingerprints, and many other characteristics. His special contribution to personality theory was that he began to think about how this thing-personality-might be measured, and thus brought within the fold of scientifically studiable entities.
In his 1884 article, he notes the general desirability of measuring personality, and comes up with some suggestions. One is that we look at natural language. Using a thesaurus, he estimates that there are at least 1000 terms describing people’s characters in the English language, but these contain a good deal of redundancy, since many of them are synonyms or antonyms. This casual observation of Galton’s began what is known as lexical work in personality, which analyses the set of descriptive terms occurring in languages as a basis for understanding the ways in which people differ. The assumption is that the semantics of natural language has developed in such a way as to mirror the important differences that exist in the world…
Galton also proposes that people have characteristically different levels of emotional reactivity-again a notion that has turned out to have some mileage in it-and suggests that we could get an index of character by subjecting people to small but impromptu emotional trials, to see how they respond (boo!) The magnitude of their response would tell us about the arousability of their emotions in general, which would be predictively useful when thinking about larger trials they might face in real life. Sir Francis is characteristically bullish about how easy this would be to do. ‘I feel sure that if two or three experimenters were to act zealously and judiciously as secret accomplices, they would soon collect abundant statistics of conduct.’ I feel sure they would, too, but I am less sure that research ethics committees would be pleased.
Finally, Galton notes the desirability of linking these reactions to physiology. If some people are more emotionally arousable than others, then this should show up in changes in heart rate or some other physiological parameters. There were technical limitations to doing this in 1884, but again, it is a very moden idea which prefigures the contemporary interest in linking personality constructs to underlying neurobiological mechanisms. Thus, Galton has already envisioned, at least in principle, many of the methods of modern personality psychology. What is missing from his account is the most common source of personality data today, namely ratings. Much modern personality work is based on people’s self-reported ratings of what they are like, or, more rarely, of what someone else is like. It is a fortunate development for personality psychology that data of this kind have turned out to be quite reliable, since they are the quickest and easiest of data to collect…
…Suffice it to say for current purposes that the central notion of personailty psychology is the trait. A trait is a continuum along which individuals vary. Nervousness might be a trait, for example, or speed of reaction…