Can You Correctly Guess These Monkeys' Emotions?

Wildlife tourists often mistake warning of aggression for smiles or kisses, leading to bites and mayhem. How would you fare?

As our very distant cousins, it's easy to see how monkeys are a lot like humans ... even if we did manage to come up with iPhones and get ourselves to the moon. So alike are humans and non-human primates that it's pretty easy to anthropomorphize and think we know what's going on in those monkey brains. Like, he's showing his teeth with an upturned mouth, he must be happy! But this isn't always the case, and the implications have an impact, as revealed in new research out from the University of Lincoln looking at human perception of facial expressions in Barbary macaques (Macaca sylvanus).

The Difficulty of Interpreting Macaques' Facial Expressions

The group of behavioral ecologists and psychologists, led by Laëtitia Maréchal, begin their paper by explaining the "universality hypothesis" that says the basic emotions of anger, disgust, fear, happiness, sadness, and surprise should be expressed in similar ways between humans and nonhuman primates. But such is not the case with macaques – a popular monkey in tourism – and the results can lead to problems. They write:

However, some facial expressions have been shown to differ in meaning between humans and nonhuman primates like macaques. This ambiguity in signalling emotion can lead to an increased risk of aggression and injuries for both humans and animals. This raises serious concerns for activities such as wildlife tourism where humans closely interact with wild animals.

All too often, wildlife tourists mistake warning signs and aggression in macaques as smiles or kisses – which leads to bites of humans and welfare woes for the primates.

"There is a growing interest in wildlife tourism, and in particular primate tourism. People travel to encounter wild animals, many of them attempting to closely interact with monkeys, even though this is often prohibited," Maréchal says. "However, serious concerns have been raised related to the safety of the tourists interacting with wild animals. Indeed, recent reports estimate that monkey bites are the second cause of injury by animals after dogs in South East Asia, and bites are one of the main vectors of disease transmission between humans and animals."

The team worked with three groups of participants – each group with varying degrees of experience with macaques – who were quizzed with photos of the monkey's facial expressions. In the end, they found that all participants made mistakes confusing aggressive faces with docile, neutral and friendly faces. Not surprisingly, the most experienced group made the least mistakes, but still mistakes were made – experts made 20.2% mistakes in interpreting aggressive facial expressions.

"Our findings indicate that people who are inexperienced in macaque behaviour have difficulties in recognising monkey's emotions, which can lead to dangerous situations where they think the monkeys are happy but instead they are threatening them."

Can You Tell the Difference?

The six various facial expressions are shown above, they represent four basic emotions: Neutral, friendly, aggressive, and distressed. Can you tell which is which? The explanations from the study are below.

(A and B) Aggressive or threat face: In the first picture (A), the eyebrows are raised, the animal stares intently and the mouth is open showing the teeth. In the second picture (B), the eyebrows are raised, the animal stares intently and the lips are protruded to form a round mouth.

(C and D) Distressed or submissive face: In the first picture (C), the mouth is widely open, and the animal is yawning. Yawning can be related to distress and anxiety in primates. In the second picture (D), the corners of the lips are fully retracted and the upper and lower teeth are shown.

(E) Friendly or affiliative face: In picture (E), the mouth is half open and the lips slightly protruded. This expression involves a chewing movement and clicking or smacking of the tongue and lips.

(F) Neutral face: In picture (F), the mouth is closed and the overall face is relaxed.

The authors discuss measures to help reduce misinterpreting the monkeys' moods, like keeping a safe distance between tourists and wild animals, lessons and videos, supervised visits with expert guides. "If we can educate people, and prevent monkey bites, we can not only reduce the risk of disease infection, we can improve on the tourism experience," note the researchers. "These findings are highly relevant to the general public and any professional in wildlife tourism, where wild animals can interact with the general public."

Not to mention highly relevant to the monkeys themselves, because just like us, surely they'd appreciate being better understood ... or am I anthropomorphizing again?

Read more here: Experience-based human perception of facial expressions in Barbary macaques