Llamas recently have become a relatively common sight around the world. Whether you live in England or New South Wales, Canada or New Zealand, you don’t have to go too far to find a llama now. Indeed between 2,000 and 4,000 llamas are registered in the UK, where the species has emerged as a popular (if seemingly unlikely) choice for many aspiring livestock owners and is winning new admirers by the day.

While the llama is currently on the up, its history has not always been so rosy. Reared intensively by the Incas, llamas suffered severely at the hands of the Spanish conquistadors and still lack the genetic diversity they enjoyed in Pre-Columbian times. But over the past few decades, llamas have flourished as a global commodity, fulfilling novel roles and gaining an international profile.

So how has the llama gone from near extinction to global sensation?

The ancestors of the llama originated in the Great Plains of North America around 40-50m years ago and migrated to South America three million years ago, when a land bridge formed between the two continents. Llamas themselves are believed to be descended from guanacos – their wild cousins – and were first domesticated around 4,500BC.

As the only livestock to be domesticated by humans anywhere in the New World, South American camelids fulfilled a role in the Andes equivalent to horses, cattle and sheep in Europe, furnishing ancient Peruvian civilisations with transportation, clothing and sustenance. They occupied a crucial place in the cultures of the Nazca (c. 200BC-600AD), Moche (c. 0-700AD), Wari (c. 600-1000AD) and Chimu (c. 1300-1470AD).

Llamas are most closely associated with the Incas, who used them as beasts of burden and sacrificed thousands of the animals every year to their gods. In the month of Capac Raymi (January), for instance, they sacrificed 100 camelids with “long wool and stiff straight tails”; in the following month, Camay (February), they sacrificed 100 “light brown” camelids, “white from the knees down, with white heads”.

While such large numbers of sacrifices might have been expected to seriously reduce llama numbers, careful management ensured that the flocks survived and prospered. The Incas refrained from killing female llamas, to ensure that stocks remained for breeding. They also developed a novel method of treating a disease called “carache” (probably scabies), burying afflicted beasts “at once, deep in the ground” to prevent them infecting the entire flock. They also conducted a census of camelids every November to calculate their number, recording the results in quipus – knotted threads employed as a form of account keeping.

Unfortunately, such careful practices were not maintained after the Spanish conquest, and the llama faced annihilation. While some wild species (such as jaguars) likely benefited from the arrival of the Spanish – and the consequent reduction of the human population of the Americas – llamas suffered the same fate as their human owners. Over-exploited for their meat, attacked by newly imported diseases and out-competed for grazing by sheep, llamas perished in huge numbers, experiencing a demographic decline of 80-90% in the first 100 years after the conquest. Llamas were initially very much victims of globalisation, their numbers plummeting dramatically during the “Columbian Exchange” of the 16th century.

But since then, llama populations have gradually rebounded and extended their range beyond South America. Between 1773 and 1778, the veterinary school at Alfort in France possessed a llama, which was examined by the famous naturalist George Louis Leclerc, Comte de Buffon. In 1805, the first llama to be exhibited in Britain was put on display at Brookes’s Menagerie in London, and by 1829 London Zoo owned two llamas. One of these – of the white variety – was described as “gently, mild and familiar”; the other – a brown animal – as “morose” with a penchant for spitting at visitors.

Today, llamas are big business and their uses have expanded to include livestock guarding, therapy and agility training.

In Peru and Bolivia, the animals continue to be used as beasts of burden in rural areas and retain some of their sacred connotations. They also appear increasingly as tourist attractions, gambolling around the Inca ruins at Machu Picchu and posing for photographs in Cuzco and other tourist hot spots. In 2014, the Bolivian government lobbied the United Nations to make 2016 the International Year of Camelids, emphasising the “economic and cultural importance of camelids in the lives of people living in areas where they are domesticated”.

Beyond South America, llamas have been employed to protect sheep, comfort the sick and stock many a hobby farm. In the US, a llama named Rojo conducts regular visits to hospitals, schools and old people’s homes in Oregon, while a golf course in North Carolina employs several llamas as caddies. Llamas have also been used in various parts of the globe to protect livestock from predators, shielding sheep, calves and poultry from attacks by foxes, wolves and coyotes.

The llama is one victim of globalisation to survive demographic catastrophe and come out the other side an international animal, loved, farmed and traded around the world.

Helen Cowie does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

The word “nice” has an unusual history in the English language.

Originally a term for “foolish”, its meaning over the centuries has morphed from “wanton” to “reserved” to “fastidious”. These days, it has become a somewhat bland and opaque description of personality: “she’s really nice.”

But its common usage hints at the characteristics that matter deeply to us.

Personality psychology can help unsnarl some of these fuzzy concepts. Recent research suggests that our tendency to be “nice” can be separated into two related but distinct personality traits: politeness and compassion.

We see these differences play out in social decision making, where politeness is linked to being fair and compassion to helping others.

A tale of two traits

Decades of research have shown that personality traits describing how well we treat others are often observed together. These are summarised by the term agreeableness, one of five broad dimensions capturing the majority of human personality.

Some of our most valued qualities — kindness, integrity, empathy, modesty, patience, and trustworthiness — are nestled within this dimension. They are instilled in us at an early age and reflect important standards through which we judge others and ourselves.

But are there exceptions to this cluster of “nice” personality traits? What about your big-hearted but foul-mouthed friend, or a well-mannered but distant acquaintance?

It turns out that agreeableness can be meaningfully divided into two narrower traits. Politeness refers to our tendency to be respectful of others versus being aggressive. It’s about good manners and adhering to societal rules and norms — what we’d see in upstanding, decent folks, or “good citizens”, if you will. In contrast, compassion refers to our tendency to be emotionally concerned about others versus being cold-hearted — what we’d see in the proverbial “good Samaritan”.

Clearly, these two characteristics often go hand in hand, but they also diverge from one other in interesting ways. For example, studies on political ideology show that politeness is associated with a conservative outlook and more traditional moral values, while compassion is associated with liberalism and progressive values.

One view is that politeness and compassion are linked to different brain systems — politeness with those governing aggression, and compassion with those regulating social bonding and affiliation. We see some evidence for this in neuroimaging research, where compassion — not politeness — is related to structural differences in brain regions involved in empathic responses.

Politeness and compassion in economic games

Our research has examined how politeness and compassion translate into different kinds of behaviours. We did this using social decision-making tasks called economic games, which involve fairness, cooperation, and punishment.

Economic games have a long history in behavioural economics and evolutionary biology, where they have helped debunk assumptions of human selfishness with evidence for our altruism.

But can altruism in these games be explained by people’s politeness, compassion, or both?

We began with the dictator game, a task in which a person is asked to divide a fixed sum of money with an anonymous stranger. Our results showed that traditional economic predictions were wrong on two counts. Not only did people not behave selfishly, they behaved in different ways depending on their personality.

Notably, polite people were more likely to split the money fairly than their rude counterparts. Surprisingly, we did not see this for compassion, which may indicate that sharing money with a stranger doesn’t necessarily arouse emotional concern.

But what if that stranger is actually in need of help? We studied this kind of scenario using a third-party recompensation game. In this task, a person observes an unfair division of money between two people and is given the chance to donate their own money to the victim.

Here, compassionate people gave away more money than their cold-hearted counterparts. Polite bystanders were not selfish per se — we know this because they were willing to part with their money in the dictator game just moments earlier. But they were no more likely than anyone else to intervene when bearing witness to the mistreatment of others.

These studies highlight some crucial differences between good citizens and good Samaritans. Polite people don’t necessarily help those in need, but they are fair-minded and peaceable. Meanwhile, compassionate people aren’t necessarily even-handed and rule-abiding, but they are responsive to the misfortunes of others.

What kind of ‘nice’ should we be?

In light of growing evidence that our personality can be changed, should we be trying to cultivate our politeness or our compassion?

Our capacity to empathise with others is often hailed as the key to healing social divisions. And while excessive politeness sometimes gets a bad rap, consider how easily society would descend into conflict if people acted aggressively and exploitatively, eschewing basic social rules.

Ultimately, good citizens and good Samaritans each have a role to play if we are to get along with others. Perhaps politeness and compassion are best captured in the principle:

If you can, help others; if you cannot do that, at least do not harm them.

Personality research suggests that although these twin virtues stem from separate strands of human nature, we can strive for both.

Luke Smillie receives funding from the John Templeton Foundation

Kun Zhao does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.

Climate change has returned to the big screen with the release of Al Gore’s An Inconvenient Sequel: Truth to Power. It’s the follow-up to his Oscar-winning documentary from 2006, An Inconvenient Truth, which raised awareness about global warming and encouraged us to reduce our carbon footprints.

The sequel puts the spotlight on climate change once again and will likely re-ignite the debate in popular culture for a whole new generation of moviegoers.

Read more: Ten years on: how Al Gore’s An Inconvenient Truth made its mark

While “big issue” documentaries do a great job raising awareness and developing attitudes on important issues, they often don’t go far enough in inspiring a “call to action” – especially one that leads to long-term behaviour change. Gore’s first film did inspire short-term action on climate change, but the effects soon faded.

As well as being artistically engaging, a successful advocacy film should encourage viewers to do something. This might be to reduce their consumption of fast food (as in Super Size Me), petition for the protection of threatened wildlife (The Cove), or adopt a whole-food plant-based diet (Forks Over Knives).

Media influence

Media can and do affect our behaviour. There is a well-established link between violent media and aggressive behaviour. Smoking in movies can encourage teenagers to take up smoking.

Less is known about the media’s ability to have a positive influence – such as encouraging environmentally friendly behaviours. Even when research is conducted, the long-term effects are rarely considered.

Read more: Fixing democracy to combat climate change: Al Gore Q&A

Some studies have looked for a direct link between viewing an environmental documentary and environmental donations. One study found that twice as many people donated to an environmental cause after watching a seven-minute environmental clip. Another found that after watching a full-length dolphin documentary, almost everyone donated to a related cause.

These studies might seem encouraging, but in both cases money was given to participants and they were asked to donate it to one of a predetermined list of charities. Sadly, this means the behaviour is unlikely to translate to the real world.

Short-lived success

In the case of Gore’s An Inconvenient Truth, individuals who watched the film reported an increase in knowledge, environmental concern, and willingness to act. Another study found that two months after the film was released, the purchase of carbon offsets increased by 50% in suburbs near cinemas that screened it.

After watching the documentary Food, Inc., which takes a critical look at America’s industrialised food industry, one of us (Kim) personally took up the challenge of avoiding processed foods. She stocked her fridge with local produce and started eating more fresh fruit and vegetables. Her friends and family also copped an earful about the difference between “food” and “food-like products” – some even adjusted their behaviours as a result.

It appears Kim wasn’t alone in her response. A study by the Norman Lear Center found that people who saw Food, Inc. were more likely to do as she did, at least in the short term (there was no follow-up study). The real challenge is in creating long-term sustainable change. Kim’s Food, Inc.-induced commitments faded within six months.

This seems to be the common trend with “big issue” documentaries. While more people intended to reduce greenhouse gases after watching An Inconvenient Truth, a survey a month later showed few had followed through.

Similarly, the increased purchase of carbon offsets failed to translate into a repeated behaviour. If customers had renewed their film-inspired purchase, the notable spike two months after its release should have been observed the following year, but this was not the case.

An unexpected win

One success story was the “big issue” documentary Blackfish, which centres on the plight of captive orcas in parks like SeaWorld. The film didn’t tell people how to feel or how to respond (it didn’t include a specific “call to action”), but since its release in 2013 SeaWorld has reported a consistent drop in visitors and revenue. In 2016 Seaworld discontinued its orca breeding program and recently discontinued the orca show itself.

Apart from its strong emotional appeal, part of the film’s success is credited to the distributor, CNN, for capitalising on the growing popularity of social media. As a result, Blackfish became the most-talked-about show on Twitter, achieving almost 70,000 Tweets on the night it was released in the US. It sparked a fierce online debate, which included celebrities and media personalities, further stimulating its reach and success.

Making change last

If documentary makers want to create long-term change, they need to do more than just pull at our heartstrings. They must include a solution message and an achievable “call to action”. Without telling viewers how they can help, they can be left feeling that it’s a lost cause and that everyone is doomed.

Advocacy documentaries should also be coupled with other behaviour change techniques to increase their chances of success. For instance, they should ask viewers to publicly pledge to change their behaviour or to set goals, give them tools to help form a new habit, or tell them exactly how to petition organisations and governments to make structural changes.

Gore’s latest film ends with a brief “call to action” – urging viewers to encourage local governments and institutions to switch to 100% renewables. It even asks for a public pledge on Twitter using the hashtag #beinconvenient. But these requests seem like an afterthought. Although the doom and gloom message is paired with glimmers of hope, watching Gore’s personal struggles against big business and politics did not leave Kim, an everyday citizen, feeling empowered.

Documentaries can be a useful instrument in the behaviour change toolkit. But lasting change needs more than an engaging story on its own.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond the academic appointment above.