Social animals need to recognize one another. Individuals are important where relationships exist for any duration, and in any community with a social hierarchy. Yet zoologists seemed surprised to learn that all social species innately possess skills that meet the need. (Aren’t humans supposed to be superior at this sort of thing?!)
At its best, human facial recognition is middling. The upside down face to the right appears normal, yes? Keep your eyes on her and wait a moment.
Don’t feel bad about being fooled with faces. Chimps too are much better at recognizing other chimps’ faces when right-side-up rather than upside-down.
A 9-minute old human baby will turn its blurry gaze to follow a face. Other moving objects do not draw such scrutiny.
A rhesus macaque just 3 days old smacks its lips and sticks its tongue out to imitate a person doing the same at the macaque. Any other provocation does not bring such a response.
Macaques are an Old World monkey that lives in troops of 20 – 200 members. In a typical troop, female macaques may outnumber males four to one. Males and females have their own social dominance hierarchies.
Females have a stable matrilineal hierarchy. A female’s rank depends on her mother’s rank. A single troop may have multiple matrilineal lines. A female outranks any unrelated female that has a lower social standing than her mother.
Rhesus are unusual in having a reverse seniority to social standing: the youngest female outranks her elder sisters. This helps mothers prevent older daughters from forming a coalition against her. Since a daughter is born with high rank that declines, and is more dependent upon mom, rebellion is put out of the picture.
Adolescent male macaques also rank in matrilineal lines, but are driven from their natal group when 4 – 5 years old. Thus, male social dominance is gained by age and experience.
If you think sheep are not sharp, sheep have pulled the wool over your eyes. Sheep are social, with relations little understood. What has been sussed out is that a sheep can remember the faces of at least 50 other sheep for at least two years. But they are no better than chimps or people in recognizing faces upside down.
The dark North American paper wasp (Polistes metricus) is best known for making its paper nests below the roofs of houses (or in trees or foliage). A female founds her own colony. She’s not good with faces.
But her close cousin, the golden paper wasp (P. fuscatus), is. Goldie females form group colonies: building a joint nest and laying eggs there.
These clustering queens squabble and determine a dominance hierarchy. So it comes as no surprise that golden paper wasps (females at least) recognize faces. While wasps don’t appear to have facial expressions (exoskeletons don’t make for pliable faces), wasp heads do have different shapes, sizes and features.
If faces are hard to see, perhaps because it’s dark, individuals are still recognizable. When they meet, rats sniff both ends, for starters. After initial investigation, they go nose-to-nose, sweeping their whiskers back and forth. Whisker touch, which tells a rat so much, also helps it recognize who it has encountered.
Susan Milius, “Face smarts,” Science News (6 October 2012).
Michael J. Sheehan, et al, “Specialized face learning is associated with individual recognition in paper wasps,” Science 334 (4 December 2011).
Alla Katsnelson, “Wasp clock faces like humans,” Nature News (1 December 2011).