Wolves and dogs can communicate using their eyes alone, suggests a new study in the journal PLoS ONE.
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.