Wednesday, February 8, 2012

Friends with Benefits

"It is not so much our friends' help that helps us
as the confident knowledge that they will help us."

-Epicurus, Greek philosopher (341 - 270 BC)

“Silences make the real conversations between friends.
Not the saying but the never needing to say is what counts.”

-Margaret Lee Runbeck, American author (1905 - 1956)

photo by Jérôme Micheletta, Macaca Nigra Project

Where would we be without our friends? Friends lend a hand in bad times and cheer us on in good times. They make us laugh, share their food, and tell us where to find interesting things… like fruit or coconuts!

Okay, so maybe finding fruit and coconuts isn’t that high on your priority list, but it seems to be pretty high on the list for crested macaques. And lucky for them, they have friends to rely on too.

Jérôme Micheletta and Bridget Waller at the University of Portsmouth in the United Kingdom set out to determine whether social factors influence the ability of crested macaques to follow the eye gaze of a group-mate and potentially gain important information. To do this, they hung out at the Marwell Wildlife Zoological Park in Winchester, U.K. every day to watch and video record the crested macaques. An experimenter would wait for two crested macaques to be within 1 meter of each other with one individual facing the experimenter (they called this animal “the informant”… not to be confused with Matt Damon) and the other individual facing the informant and facing away from the experimenter (they called this animal “the subject”). You can imagine, this process involved a lot of waiting around. Once the animals were in place, the experimenter held up a yummy treat (an orange, a banana, or a coconut). The informant would see the treat and then the subject would either look at the treat or not. In these cases, the subjects looked at the treats 64% of the time.

This figure from Micheletta and Waller's Animal Behaviour
paper shows their experimental procedures.
But how do we know that the subjects followed the informants’ gaze and didn’t respond to something the experimenter or some distant cage-mate did? Micheletta and Waller also recorded the responses of the same animals in a control situation: the experimenter would wait for a subject to be away from its cage-mates, but with its back turned to the experimenter. Then the experimenter would hold up the yummy treat. In these control trials, the subjects looked at the treats only 7% of the time.

So it looks like crested macaques use their peers’ eye gaze as information on where to look. They also were faster to look if their cage-mate moved his/her head in combination with an eye movement, rather than just the eyes. But, does the social context matter? For each pair of macaques, Micheletta and Waller calculated the relative dominance status and friendship strength. They used months of observations of aggressive encounters in which they knew the winners and losers of each encounter to rank the overall dominance hierarchy of each animal in the group. A typical aggressive encounter either involved one monkey chasing another (which would either run away or crouch) or a monkey approaching another and taking away his/her food or grooming-buddy or mate (How rude!). They also determined friendship strength by calculating the average number of times they sat in contact with or groomed a specific individual versus other animals in the group.

If the informant was a friend, the subject was quicker to look at the food than if the informant was not a friend, although friendship did not influence the overall success rate. And the relative dominance status didn’t seem to have any effect.

Why might macaques follow their friends’ gazes faster than nonfriends’ gazes? Maybe they are generally more visually attentive to their friends than their nonfriends, as is true in chimpanzees, siamangs, chacma baboons and ring-tailed lemurs.  Or maybe a friend’s information is more relevant than a nonfriend’s information. Friends often share motivations and needs and often compete less and share more with each other than with nonfriends (although there are many exceptions to this, as you may have experienced). All of these possibilities leave open new avenues for future research. But one thing is clear: It sure is good to have friends.

Want to know more? Check this out:
Micheletta, J., & Waller, B. (2012). Friendship affects gaze following in a tolerant species of macaque, Macaca nigra Animal Behaviour, 83 (2), 459-467 DOI: 10.1016/j.anbehav.2011.11.018

Do you have a thought on friends that you would like to share? Comment below.


  1. Cool, although an anti-climax given the title of the article

  2. That's cool. I was expecting that maybe with a dominant informant, the subject would not look. But the idea about friendship leading to a faster reacting is really interesting.

    1. I was surprised too with the results of the dominance analysis, but even in less tolerant species, individuals tend to pay more attention to dominant individuals, probably because they need to know what they are doing, maybe to be able to avoid conflicts.

    2. I was also surprised by the lack of effect of dominance status on whether the subject looked and how long it took to look. It could be a reflection of the tolerance of the species. But now I wonder if dominance affects whether the subjects act on the information (e.g. approach the food item). Maybe to a tolerant and dominant crested macaque, a subordinate being aware of a food item is not as much of a problem as a subordinate approaching or consuming the food item.

    3. that would be for another study :)