The importance of owners maintaining a rich and fulfilling relationship with their horses is highlighted in the findings of a recent study.
Researchers showed that horses not only discriminate between individual human voices, but have a recollection of whether their past experiences centered around each voice was positive or negative.
In other words, past experiences dictate whether your horse is happy to hear you, and presumably see you, each day.
Scientists from Italy and France noted that evidence about the interplay between sound-related memories and prior emotional experiences in horses was largely unknown, which spurred them to carry out an experiment.
They hypothesized that horses may associate particular human voices with the positive or negative nature of earlier experiences.
For their study, reported in the journal Scientific Reports, they used 21 horses – a mix of riding center and leisure mounts.
For seven consecutive days, they exposed the horses to a positive experience (a bucket containing food), or a frustrating one (a bucket of food soaked with vinegar) while hearing one of two different human voices reciting the same text played through a speaker worn by a silent experimenter who presented the bucket.
One of the voices was always associated with the positive experience and the other was always linked with the negative experience.
After the seven days, aiming at creating sound-related memories, the reactions of each horse to the voices was assessed based on their behavior and electroencephalogram (EEG) results, the latter providing information about their brain electrical activity.
The researchers, from the University of Rennes in France and the University of Bari Aldo Moro in Italy, reported that the two voices were clearly differentiated by the horses.
There was, they said, more right head-turning for the voice linked to the positive experience when the horses were free to move.
“The right bias found here suggests the left hemisphere advantage for processing the ‘positive’ voices,” Serenella d’Ingeo and her colleagues reported.
The horses spent more time with the loudspeaker on their left side while the negative-linked voice was being broadcast.
When held, the horses spent most of the time with the ears forwards during the playback of the positively linked voice, whereas they spent more time with their ears back when the negatively linked voice was played.
Anecdotally, three horses pulled the rope to turn their head and body toward the source of the positively linked voice, or even approached it (one of them with a nicker); while seven pulled the rope to increase their distance from the source of the negatively linked voice.
Results for the EEG confirmed the horses’ different reactions to the voices.
“This study confirms that horses do discriminate human individual voices but also reveals that they have a memory of the valence of past experiences with these voices,” the researchers reported.
Human voices associated with previous positive experiences elicited a positive response in the horses and drew their attention, whereas human voices linked with past negative experiences produced a negative affective state.
“Overall,” they concluded, “both behavioural and electrophysiological results demonstrate that horses not only associate human voices with the valence of previous experiences with humans, but they also recall the valence of such experiences when hearing human voices.
“These findings support anecdotal reports of long-term memories of past experiences with humans.
“They also confirm the evidence that horses build representations of humans that are influenced by daily interactions or training modalities.
“Therefore, the valence of previous interactions can affect horses’ future attitude towards humans and their behaviour.”
The researchers found that the riding centre horses, which lived in restricted conditions, appeared to be more sensitive than leisure horses to the different valences of the prior experiences associated with human voices.
The full study team comprised Serenella d’Ingeo, Angelo Quaranta, Marcello Siniscalchi, Mathilde Stomp, Caroline Coste, Charlotte Bagnard, Martine Hausberger and Hugo Cousillas.
Horses associate individual human voices with the valence of past interactions: a behavioural and electrophysiological study.
Serenella d’Ingeo, Angelo Quaranta, Marcello Siniscalchi, Mathilde Stomp, Caroline Coste, Charlotte Bagnard, Martine Hausberger and Hugo Cousillas
Scientific Reportsvolume 9, Article number: 11568 (2019) https://doi.org/10.1038/s41598-019-47960-5
The study, published under a Creative Commons License, can be read here.