© Doug Smith, National Park ServiceA wolf rests in the snow at Yellowstone National Park.
The color of the face around the eye, the eye's shape and the color and shape of both the iris and the pupil are all part of the elaborate eye-based communication system, according to the research, which could apply to humans as well.
Sayoko Ueda of the Tokyo Institute of Technology and Kyoto University led the study, which compared these characteristics of the face and eyes among 25 different types of canines.
The researchers identified three basic patterns:
A-type: Both pupil position in the eye outline and eye position in the face are clear.
B-type: Only the eye position is clear.
C-type: Both the pupil and eye position are unclear.
"A-type faces tended to be observed in species living in family groups all year-round, whereas B-type faces tended to be seen in solo/pair-living species," Ueda and colleagues wrote.
Wolves and dogs exemplify the A-type. Humans fit into this category too! Such individuals invite you to look into their eyes. The researchers even suspect that the white of the eye (sclera) evolved, in part, to set off the darker hues of the iris and pupil.
Animals like foxes exemplify the B-type. For them, some information is likely conveyed by the eyes to others, but not much.
Then there is the elusive C-type, exemplified by animals like bush dogs. Their all-dark eyes blend in with their furry faces. The researchers point out that "various predators camouflage their eyes to increase their hunting success." Consider that if you don't know what an individual is looking at, you can't predict his or her behavior.
Following the eyes can reveal interests and where an individual might go next. Both wolves and dogs are adept at following human gazes.
"The fact that the studied (canine) species with A-type faces tended to engage in group living suggests that they use the gaze signal in communication among group members, as the need for communication is larger for group-living species than for solo/pair-living species," the researcher wrote.
They added, "Group-hunting species had significantly lighter iris color (an important factor of gaze-signaling eyes) than those of solo hunting species. These results suggest that the gaze signal is used for communication during group hunting in many of these species."
Since we're social mammals too, perhaps we are revealing more about ourselves and our mental states with our eyes than we fully realize.
I wonder if people subconsciously communicate a little information with each other when they look in each others' eyes. People had to communicate some way before language (though I also wonder if humans didn't exist until after there was a language for them to use, handed down from an ancestor) and maybe it wasn't just grunts, facial expressions etc.
I remember once I had a pot of few cannabis sprouts hidden outside a little distance from my disapproving parents' house that I was living in and I was out with my dog when my mom walked out to find her and bring her back inside. I went to when she came across us and to get back to the house we had to walk near the pot of pot, and I was nervously glancing over and looking in that direction out of the corner of my eye between alternating nervous glances at my mom, who was oblivious. My dog had been near it before and seen me tending to it and I swear she knew what was going on by the look she gave me. She probably didn't know all the details and exactly what I was doing with the pot of course but she gave me a mischievous look when we'd gotten far enough out of sight of the pot.