Horses can tell when human facial expressions and tone of voice match, according to a new study.
Pet owners have always felt that they bond with their dog or cat and that their pet understands, communicates with, and loves them.
Recently, science has been backing up the pet owners' feelings.
Similarly, other studies have shown that the kind of "baby talk" that humans use with their infants and sometimes with their pets also makes dogs bond with them and prefer them to other people.
Dogs can also recognize a smile, and the secretion of oxytocin makes them prefer the smiling faces of humans over danger cues.
Many people have similar warm feelings toward domestic horses. But do horses possess the same ability to recognize and respond to human emotional cues? This question prompted three Japanese-based researchers to investigate.
Associate professor Ayaka Takimoto, of Hokkaido University, graduate student Kosuke Nakamura, of the University of Tokyo, and former professor Toshikazu Hasegawa, of the University of Tokyo collaborated on the new study, which was just published in the journal Scientific Reports.
The expectancy violation method
To find out whether horses respond to human emotions by integrating facial cues with the tone of voice, the researchers used the so-called expectancy violation method, which is a method commonly used to assess cognitive development in infants.
In this study, horses were shown pictures of happy or angry human facial expressions on a screen. Then, they heard gentle or scolding voices behind the screen.
The emotional value of the voices and pictures sometimes matched, in the so-called congruent condition, and sometimes they didn't, in the incongruent condition.
The researchers also accounted for the familiarity between the horses and the humans by alternating the voices of their caretaker with those of strangers.
How horses respond to human faces, voices
The study revealed that in the incongruent condition, the horses responded to voices 1.6 to 2 times more quickly than in the congruent one.
The horses also looked at the speaker for significantly longer in the incongruent condition than the congruent one, when the voice was that of their caretaker, but not when it was that of the stranger.
These findings suggest that, when the horses heard a voice whose emotion did not match the facial expression, their expectancy was violated. Therefore, the authors conclude, horses normally respond to human facial expressions and voices in an integrated way.
"To the best of our knowledge," conclude the researchers, "this is the first study to show that horses cross-modally recognized the emotional states of their caretakers and strangers."
"Our study could contribute to the understanding of how humans and companion animals send and receive emotional signals to deepen our relationships, which could help establish a better relationship that emphasizes the well-being of animals."