Horses, like dogs, cats and other animals, use various vocalizations to express themselves. Swiss researchers have studied the vocalizations enough to understand what emotions the horses are displaying when they make them, reports EQUUS magazine.
Drs. Briefer, Maigrot, Mandel, Freymond, Bachmann and Hillmann, from the Institute of Agricultural Sciences at ETH Zurich, used 20 horses and triggered whinnies using specific situations that were designed to evoke positive or negative reactions from each of the horses. The researchers used separation from other horses to evoke negative reactions and reunions with the horses to evoke positive reactions in the horses. They also studied the intensity of the reactions by monitoring each horse's heart rate.
The team recorded and studied the acoustical properties of each horse, determining that each noise had two frequencies: two fundamental frequencies (G0 is the higher frequency and F0 is the lower frequency) and their multiples, called harmonics. Having two fundamental frequencies is rare in mammals; even rarer is the fact that all the horse's whinnies used both frequencies.
Equine whinnies typically begin higher and add in the lower frequency. Though this is not completely understood, the researchers believed it is most likely from the asynchronous vibration of the vocal folds.
The scientists were also surprised to learn that the lower the whinny, the more emotionally aroused the horse, such as one who has intense feelings like fear; if the horse whinnies in a higher pitch, it's expressing an emotion, like joy or fear. When an emotion becomes more intense, F0 increases. In a positive emotion (not related to arousal), the G0 becomes lower.
They conclude that positive whinnies start with a lower frequency and are shorter in duration. Negative whinnies start higher and last longer.
Read more at EQUUS magazine.
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