When we observe an interaction between two other human beings
(Person A and Person B), we sometimes draw conclusions about the personality
traits or character of these two individuals. For example, if we see that
Person A is being rude to Person B, we may be less likely to trust Person A, even
though we are merely "third-party" evaluators. i.e. not directly involved
in the interaction. Multiple studies with humans have already documented such
third-party social evaluation, which can even occur among children. A study
published in 2010 showed that 3-year old children were less likely to help
adults who had previously acted in a harmful manner in front of the kids, i.e. torn
up a picture drawn by another adult in a staged experiment.
Do animals who observe humans also conduct such third-party social
evaluations of humans? The recent study "Third-party
social evaluation of humans by monkeys" published in Nature Communications by James Anderson
and colleagues staged interactions with human actors in front of tufted
capuchin monkeys (Cebus apella). The
researchers found that the monkeys indeed evaluate humans after witnessing
third-party interactions involving either helpful interventions or a failure to
help fellow humans.
In front of each monkey, two actors performed either
"helper" sessions or "non-helper" sessions. In the "helper"
sessions, Actor A tried to get a toy out of a container and requested help from
Actor B, who complied and helped out Actor A. In the "non-helper"
sessions, Actor B refused to help. After the sessions, both actors offered a
piece of food to the monkey. In the helper sessions, monkeys readily accepted
food from both actors. On the other hand, monkeys in the non-helper sessions accepted
food more frequently from actor A (the requester of help) than Actor B (the non-helper).
The researchers also added an interesting twist to the experiment
by creating a situation in which both actors had their own containers. The
researchers then created an "occupied non-helper" condition in which
Actor B did not even acknowledge Actor A's request because Actor B was pre-occupied
by their own container. In this "occupied non-helper" situation, the
monkeys accepted food from both actors equally. In an "explicit non-helper"
condition, Actor B acknowledged the request for help from Actor A but explicitly
rejected the request. In this latter situation, the monkeys were less likely to
accept food from Actor B.
This study is not the first study to evaluate third party social
evaluations of humans by non-human primates, but its strength lies in its meticulous
design. Both actors offered the same type and amount of food to the monkeys, so
that the most likely explanation for the monkeys' choices was indeed the
interactions of the humans with each other.
The research presented in this study gives us a fascinating
insight into how third party social evaluations by non-human primates. The fact
that the monkeys discriminated between occupied non-helpers (i.e people who were
too busy to notice the request for help) and explicit non-helpers (i.e. people
who were just plain mean - they noticed the call for help but rejected it) shows
a very fine-tuned analysis of human interactions. It is a good reminder of how
human interactions can leave lasting impressions on fellow beings - humans and
non-humans.
Image credit: Adult Tufted Capuchin by
Charles J Sharp, via Wikimedia Commons (Creative Commons License).
Anderson, J., Kuroshima, H., Takimoto, A., & Fujita, K. (2013). Third-party social evaluation of humans by monkeys Nature Communications, 4 DOI: 10.1038/ncomms2495
