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Human behaviour has long been an intriguing topic of research for scientists.

Different forms of human behaviour often present together. People who are outgoing are also likely to be assertive. People who are shy at work are less likely to be a party animal at a bar on Friday night. 

This forms the basis of personality, a series of behaviours held by an individual that remain reasonably stable through different contexts and over time.

But what decides a person’s personality? Researchers say it is not random, and also not down to just genetics.

A recent study by researchers at UC Santa Barbara, California State University Fullerton, UC Merced and the University of Richmond has found that social and ecological environments influence how we develop, and our personalities. 

They argue that the reason humanity is made up of so many different personality profiles is because society also varies in a variety of socioecological niches.  

The researchers wanted to find if increasing the number of niches resulted in more personality types. They created a model to test how a variation in niches impacts personality types. 

They explain that each niche has an ideal personality type, a person who wishes to be a loner might not want to live in New York City, for example. Niches are made up of occupational, social and other specializations of life like hobbies and clubs. 

They hoped to test the theory that societies that are more complex, with multiple niches, will also have greater diversity in personality types. 

In psychology, personality traits are often discussed in reference to the Big Five. This group of dimensions has long been used by psychologists to universally define human personality structure. 

“The Big Five refer to five dimensions along which personalities have been shown to vary: Extraversion, Openness, Conscientiousness, Agreeableness and Neuroticism/Emotional Stability. These dimensions are "extracted" from complicated statistical analyses of self-report or others reporting on how someone scores on many different behavioral traits,” Michael Gurven, a professor of anthropology at UC Santa Barbara and the paper's senior author told Theravive. 

“The dominant model for personality in much of psychology is the Big Five. Yet no one really knows why the Big Five might best represent the structure of human personality, it just seems to fit the data. But what happens when it doesn't fit the data? Most critiques are explained away by Big Five advocates as being merely methodological. We wanted to see if we can build from the ground-up a more theoretical basis for why personality structure might vary across populations. We had earlier found some interesting differences in personality structure among 55 nations, and so thought we might be on an interesting track,” he said.

Gurven and his colleagues found through their model that whether looking at a population of 100 or a thousand, increasing the number of niches caused personality traits to mirror those in the Big Five. Increasing the number of niches resulted in less correlation between personality traits. 

“We found that when you increase the number of niches in the environment, and allow individuals to disperse to the niche where they might have a better fit, that personality structure at the population level will look more like the Big Five -- that is, more factors are needed to explain personality. Greater divisions of labor and specialization leads to a larger range of personality types in the environment,” Gurven explained. 

The researchers say their model could be used to better understand the evolution of human personalities and behaviour.

“Our model could be applied to understanding broad changes in people after the Neolithic transition moving from hunting and gathering lifestyle to one based on farming and increasing economic specialization. Then society moved to early industry and further divisions of labor and economies of scale, and urban areas in nation-states where many live today. How did those shifts in society affect (and may be affected by) the types of personalities present in the population? Do some personalities "fit" better in some occupations or circumstances more than others?” 

Gurven argues the influence of ecology and culture on personality is not yet fully appreciated.    

“We need to take seriously the notion that while we're all the same in some sense, culture and ecology can shape who we are and how we express ourselves in fundamental ways, that are not well appreciated. Part of the reason is the long-standing focus in psychology on convenience samples of undergraduate student populations,” he told Theravive.