Are horses motivated more by a tasty morsel or a good, old-fashioned scratch?
Food, it seems, is the hands-down winner.
That was the conclusion reached by French and Polish researchers, who evaluated the pulling power of pieces of carrot against a decent scratch on the withers during a training task.
Carol Sankey, Séverine Henry, Aleksandra Górecka-Bruzda, Marie-Annick Richard-Yris and Martine Hausberger devised a simple experiment in which Konik horses were rewarded by one of the two methods when taught to stand still for a period of time.
Their findings indicated that humankind – a tactile species – may mistakenly believe horses derive more benefit from the human touch than is actually the case. In short, they suggest that horses simply aren’t the touchy-feely type.
“While in some species, like humans, physical contact plays a role in the process of attachment, it has been suggested that tactile contact’s value may greatly differ according to the species considered,” the researchers noted.
“Nevertheless, grooming is often considered as a pleasurable experience for domestic animals, even though scientific data is lacking. On another hand, food seems to be involved in the creation of most relationships in a variety of species.”
The research, published in the open-access journal, PLoS ONE in 2010, involved the use of 20 Konik horses, a primitive breed originating directly from the wild Tarpan horse.
The horses were randomly allocated to one of two training groups: the food-reward group, in which the experimenter hand-gave a small piece of carrot to the horse when it responded correctly to her command; and the grooming-reward group, in which the experimenter vigorously scratched the horse’s withers three times when it responded correctly to her command.
Subjects underwent a training program to learn to remain immobile on the voice command: “reste!”, for an increasing duration, from 5 to 60 seconds.
Training was performed for 5 minutes a day for six days and took place in the horses’ home stable.
In addition, the researchers performed a “motionless human test”, in which horses were free to interact with the person standing in the center of the stable for five minutes.
“Clear differences occurred both in learning performance and in the relationship to humans according to the type of ‘reinforcement’ used,” the researchers found.
While on the last day of training, nine out of 10 horses trained with the food reward had successfully reached the last step and managed to maintain immobility for 1 minute, only four of the grooming-rewarded group managed the task.
Food-rewarded horses progressed rapidly, especially during the first three days of training, the researchers noted, while the groomed horses’ progression was limited to the first two days of training, after which they stagnated.
The researchers also found that the food-rewarded training had a more positive impact on the animals’ relationship with the person, based on their approaches and interest during the “motionless human test”.
The researchers, from the University of Rennes 1 and the Polish Academy of Sciences, concluded that using food rewards had beneficial effects on horses’ attachment to humans and aided learning, whereas grooming was clearly not perceived sufficiently positively, neither for bonding to occur, nor for enhancing learning.
“Food-rewarded animals learned the immobility task faster than grooming-rewarded animals. In fact, the performance of the latter on the sixth day of training was very close to that found in control horses trained to the same task in a previous study,” they found.
“Grooming the withers therefore does not appear to be an efficient reinforcement for horses.”
They continued: “Because we humans are sensitive to tactile stimulations, we often assume that stroking or other forms of gentling animals have positive effects.
“This may indeed be the case for some species, but this study clearly demonstrates that inter-species differences are to be expected: the results suggest that human tactile contact, even when imitating intra-specific natural interactions, is not necessarily perceived positively and is surely not sufficient to create attachment.
“In horses, physical contact is very restricted through occasional licking of the young by its dam and later mutual grooming; it only represents 2–3% of their time-budget and is often restricted to specific body regions.
“Studies have reported that grooming at the withers, whether performed by a conspecific or a human handler induced a decrease in horses’ heart rate. However, grooming was performed for a much longer duration ( about 3 minutes) and a decrease in heart rate does not mean that it is perceived sufficiently positively to be considered as reinforcement and thus promote learning or bonding.”
Food, they concluded, appeared to be one of the keys in the bonding process in the human-horse relationship.
“There is an idiomatic expression that says: ‘the way to a man’s heart is through his stomach’. It seems that this may not only apply to humans, but could indeed be the case for many species, [including] horses.”
Sankey C, Henry S, Górecka-Bruzda A, Richard-Yris M-A, Hausberger M (2010) The Way to a Man’s Heart Is through His Stomach: What about Horses? PLoS ONE 5(11): e15446. doi:10.1371/journal.pone.0015446
The full article can be read here.