Caleb Sooknanan ‘20

Horses can cross-modally, or with multiple senses simultaneously, distinguish human facial expressions and recognize people with whom they are acquainted. While horses may be able to cross-modally distinguish human emotions, more research is needed to understand these animals’ cognitive abilities. Doctor Toshizaku Hasegawa and researchers from Hokkaido University in Japan conducted a study in which the expectancy violation method — normally used to explain the unexpected behaviors of human beings during their interactions — to investigate whether horses could cross-modally recognize human emotion by integrating facial expression awareness with voice tone awareness.

To perform the study, the researchers first obtained 19 horses from the University of Tokyo and Tokyo University of Agriculture and Technology; the researchers verified that the horses directly knew their caretakers for at least three months. The researchers then collected emotional stimuli from the caretakers and strangers who shared the same sexes as the caretakers. Photos of happy facial expressions and angry facial expressions were displayed on a screen in front of the horses. Gentle and scolding voice recordings of the participant horses’ nicknames were then played. The horses were subject to the congruent condition by which the emotional values of facial expression and vocal tone were equal, and the incongruent condition by which the emotional values were different from each other. The researchers recorded the horses’ behavioral responses by measuring their total looking times and response latency times.

With a resulting p value of 0.002, the interaction between familiarity and emotional congruency was significant. Horses were shown to respond to voices 1.6 to 2.0 times faster in the incongruent condition than in the congruent condition despite familiarity conditions. The study’s results also showed that the horses looked to their speakers 1.4 times longer in the incongruent condition than in the congruent condition when the speakers were more familiar to their horses. The researchers thereby suggested that an expectancy violation occurred when horses heard human voices, with the associated emotional values not being equal to those of the corresponding facial expressions. More comparative studies among domesticated and non-domesticated species would be necessary to verify that horses can use cross-modal emotional perception. Nevertheless, the study’s results provided evidence regarding cross-modal perception of human emotions with auditory and visual signals among horses.

References

1. K. Nakamura, A. Takimoto-Inose, and T. Hasegawa. Cross-modal perception of human emotion in domestic horses (Equus caballus). Scientific Reports 8 (2018). doi: 10.1038/s41598-018-26892-6.  
2. Image retrieved from: https://www.goodfreephotos.com/albums/iceland/other-iceland/icelandic-horses.jpg