2 6 ORIGIN #2
jaargang 11, december 2015
Personality matters! By Christian Tudorache, Hans Slabbekoorn and Marcel Schaaf
People differ! There are fat ones and slim ones, short ones and tall ones, stupid ones and smart ones. But people differ especially in their character. In order to be able to suggest different personalities, these differences have to be consistent over time and across context. This means that differences remain even in the face of experience gained or adaptation to new situations. This also means, that differences are distinguishable in a social setting, between individuals in relation to each other. These differences are characterised in humans within the ‘Big Five’ personality traits. These are five broad domains or dimensions that are used to describe human personality, also known as the five-factor model. These five factors are openness, conscientiousness, extraversion, agreeableness, and neuroticism. Beneath each factor, a number of correlated and more specific primary factors are clustered: e.g., extraversion includes such related qualities as gregariousness, assertiveness, excitement seeking, warmth, activity, and positive emotions.
when it contains a variation of individuals of different constitutions. More proactive individuals are typically bold, aggressive, and dominant. However, they also need to follow a behavioural routine, learn faster, but are less flexible to changes, than more reactive individuals. They generally flourish in stable, resource-rich environments at high population densities, while reactive animals flourish at low densities, where resources are sparse and unpredictable.
Personalities, however, are not reserved exclusively to humans. Inter-individual differences in behaviour, physiology and even genetics, which are consistent over time and across context, have been shown in a large number of species from our nearest relatives, the apes, over common pets such as dogs cats and fish, down to less agreeable creatures such as cockroaches and spiders. In this case we talk about animal personalities, in order to distinguish them from our rather complex concoctions of behaviours and little ticks, which make us the individual who we are. Animal personalities have been given various names, according to the field of study occupied with the subject, such as coping style in medical research or behavioural syndrome in ethology. Here, too, five axes of behaviour have been described, which are more or less correlated, depending on the species, population or family. These are aggressiveness, activity, exploration, sociability and competitiveness. A certain concurrence profile of these axes defines a behavioural type, i.e. where you are on each of the axes. Extremes are named proactive and reactive, for scoring higher or lower on each axis, respectively. A proactive individual is therefore bold, aggressive and competitive, while a reactive is shy, docile and less competitive. Again, this makes only sense in a social context, since individual A can only be that much more aggressive, bold or explorative than individual B.
These variations are generally represented in equal numbers within a population. However, when it comes down to dust, it is the extreme individuals that save the day (or will be saved). In a simple but strikingly genius experiment, Allison Bell and Andrew Sih defined the behavioural types of a number of sticklebacks along two behavioural axes: boldness and aggressiveness. The outcome was random, there were extremes of very proactive animals with a high aggressiveness-boldness score and reactive individuals with a low score, but also individuals which showed low ratings for boldness but high ratings for aggressiveness were present, and vice versa. With other words, the population was diverse and mixed. Then, they introduced a predator, a large trout, and waited for nature to take its course. After the scientists re-evaluated the survivors of this predatory feast, they discovered that these survivors were all to be found along a proactive-reactive axis. The trout ate mainly individuals, which were aggressive but not very bold, and bold but not very aggressive. They concluded that a population under stress is reduced to its extremes. In other words, curious, but not very tough individuals don’t survive the attack, nor do the bullies with little guts. It feels good to think that nature can be just.
In nature, this variation in behaviour has numerous advantages. A population is so much stronger and more flexible
However, it is important for a population to include a variety of behavioural types. In the 90s of the last century, the financial sector favoured little men with big egos, aggressive, loud and terribly short-sighted types. These ‘Wolfs