Is personality unique to humans?

By Adam Hart
Professor of Science Communication, University of Gloucestershire

image copyrightNicole Milligan
image captionA team from the University of Oxford has been studying boldness and shyness in great tits

We like to think humans are pretty special.

Given our many achievements (I don't see chimpanzees landing probes on comets in the near future) it's a tendency that's largely justified.

But most of our thoughts aren't consumed with the magnificence or otherwise of our species. If we're honest, most of our thoughts are taken up by us as individuals.

Central to this conceit is the notion of our "personality". However, while we might think that our sparkling personalities are something unique, psychological research tells us that we can assess and measure personality using just five main personality dimensions.

What's more, not only are our personalities not quite as special as we might think, recent animal research tells us that personality is not even something unique to humans.

Research into animal behaviour has usually focused on behaviour across a species, or more accurately, across a sample of that species. The approach has examined "average behaviour" and individuals only featured as data points, with variation between individuals being of far less interest than the description and explanation of the overall behaviours observed.

Recently though, there has been a shift in this view. Inter-individual variation between animals is no longer being dismissed as statistical noise but instead has been embraced and studied.

As you can hear in Frontiers on BBC Radio 4, insights from this individual-focused research have led us to a far more nuanced view of behaviour and the evolutionary processes that have shaped it.

This approach to animal behaviour has become known as animal personality research. For a field notoriously sensitive to claims of anthropomorphism it might seem strange that a word so intrinsically human, with "person" so central to its etymology, has been embraced.

But actually it's not so surprising. Human personality is all about repeatable behavioural tendencies within an individual; in other words, we tend to respond to similar situations in a broadly predictable way.

media captionScientists probe personality differences in albatrosses using a plastic toy

Some of us want to be the centre of attention while others shy away. Extroverted people tend to always be extrovert and indeed extroversion/introversion is one of the five dimensions of human personality.

For an example of why personality is also a suitable word to apply to animal behaviour, consider a creature that is probably not top anyone's list of personality candidates: the hermit crab.

Rather than growing their own expensive protective shell, hermit crabs use what Mark Briffa, reader in animal behaviour at the University of Plymouth, describes as a "dodge". They install their soft worm-like rear ends into an empty periwinkle or whelk shell, poking their heads, claws and legs out of the opening to move around.

image copyrightSPL
image captionSome hermit crabs venture out of their shells more readily than others

When disturbed, they disappear back into the security of their shell, only venturing back out when they feel it's safe. What Mark has discovered is that some hermit crabs are bolder than others, with brave crabs resuming their out-of-the-shell activities far more rapidly than shyer individuals. The crucial thing, as Mark says, is "if this behaviour is consistent within an individual then it is a bold individual".

Mark has indeed found that some hermit crabs are always bold; in other words they display a behavioural tendency that is consistent within an individual. As he explains, "that is a bit of mouthful to say, so personality seems like a good word for it".

This consistency of behaviour within an individual, or personality, has been documented in an ever-growing list of species, from obvious candidates like chimpanzees, through to cat sharks (who have social and solitary individuals) and even sea anemones. One group of animals where personality research is particularly far advanced is birds.

Wytham Woods, just outside Oxford is one of the most important field research sites in the world for studying the links between ecology, evolution and behaviour. Here, Proessor Ben Sheldon, Dr Ella Coles and others from the University of Oxford have been studying the personalities of a common bird, the great tit.

image copyrightAndy Murch/SPL
image captionResearch in the Bahamas suggests that individual lemon sharks also have their own personalities

By catching birds and exposing them to a novel environment (an aviary in which they are temporarily housed) researchers have been able to measure boldness and shyness in individuals and show that individuals are consistent in these personality traits throughout their lives.

The researchers can also follow birds over time and this long-term approach allows the team to unpick the links between personality and how successful those birds are at the fundamental business of producing offspring.

Dr Samantha Patrick of the University of Gloucestershire cut her research teeth in Wytham Woods but has subsequently moved on to rather bigger birds - albatrosses. Samantha uses an intriguing, and frankly amusing, method for determining how bold an albatross is.

Lying low in the cold grass of the Crozet Islands in the southern Indian Ocean, she pushes a toy plastic cow towards the birds with a stick. This novel stimulus allows her to measure the response of a bird, and to measure that response over time.

What she has found, just like many other researchers on a variety of different species, is that different individuals have different responses (or personality types) but that individuals are consistent in their own response.

Research on birds and on an increasing variety of species shows that generally there isn't a "best" personality to be. The reason why there is personality variation between different individuals is because there is variation in the environment.

image copyrightAFP
image captionChimpanzees are thought to share the "big five" personality dimensions - such as extroversion and agreeableness - with humans

It's a complex world out there and that complexity changes over space and time. The environment doesn't stay constant and in some environments, perhaps those with plenty of hungry predators, it pays to be a little careful, a bit shy.

In other environments, or perhaps in the same place but later in the year when food is scarce, it pays to be bold, to get out there and find those scant resources rather than cowering in a safe hidey-hole. The shifting nature of the environment means that the ultimate pay-offs to these different strategies end up being more-or-less equal and natural selection has led to a variety of personality types in animals.

Interpreting the evolution of animal behaviour in terms of their ecology is the realm of behavioural ecology and It should come as no surprise to us that evolutionary and ecological perspectives have been so useful in explaining animal personalities.

Animal personality research is now starting to move towards a deeper understanding of how different personality types evolve and how they interact in groups of animals. Research at Wytham Woods for example is looking at how personality types function in the groups of birds that form foraging flocks over winter and how that mix of personalities affects success.

Although we often like to think otherwise, our personalities are just as much the products of natural selection and evolution as our upright stance and large brains.

Animal behaviour researchers may have borrowed the concept of personality from human psychologists but as social animals living in a complex world it will be interesting to see what human psychology takes from animal research over the coming years.

Frontiers : Animal Personality is on BBC Radio 4 on Wednesday 10th December at 9pm

More on this story