Stress and temperament have an influence on the learning ability of horses, but it is not altogether simple, French researchers have found.
The scientists used 49 female Welsh ponies aged around seven, who were randomly divided into three groups.
One group of 15 was stressed before a learning task, the second group of 15 was stressed after the same learning task and the third group, of 19 animals, was not stressed at all.
The stress procedure involved exposure to 20 unpredictable sudden events, from unfamiliar objects to loud sounds and sudden movements.
The horses were bred together at the experimental unit of the National Institute for Agricultural Research in France and were accustomed to being handled.
Each of the animals was assessed beforehand for temperament using a method adapted from previous researchers. It assessed five dimensions – fearfulness, group sociability, reactivity to humans, level of locomotor activity, and sensitivity to touch.
The learning task involved training each horses to touch a cone on the ground with its nose to obtain a food reward.
The learning task was repeated a week later to determine whether there was any differences between the three groups.
The aim of the study, which has been published in the open-access journal, PLoS ONE, was to determine whether the timing of stress affected learning performance, and whether temperament influenced stress-related performance.
The study showed that learning performances varied according to the exposure to stress.
Horses stressed before the learning task tended to perform more successes at the beginning of the learning session than the non-stressed horses.
Eight days later, during the re-learning session, the non-stressed animals improved their performance.
Contrary to the non-stressed group, the horses that had been stressed after the learning task, and, to a lesser extent, those stressed before, did not significantly improve their performance.
The researchers found that temperament influenced learning performance, but only when the learning or re-learning performances were affected by stress, suggesting that temperament had little influence on learning ability provided lessons occurred in a stress-free environment.
They found that while direct exposure to a stressor tended to increase learning performance, the state of stress induced by the memory of a stressor during efforts to re-learn or reinforce the task impaired performance.
Further, the negative effect of a state of stress on re-learning the task appeared to be stronger when exposure to the stress occurred after rather than before the learning session.
The results, the researchers said, suggested that stress impaired more cognitive abilities in fearful horses than in less fearful horses.
“The present study constitutes the first evidence that stress modulates the influence of temperament on cognitive abilities in horses,” they wrote.
The research was supported by funding from the Institut Français du Cheval et de l’Equitation.
Valenchon M, Lévy F, Prunier A, Moussu C, Calandreau L, et al. (2013) Stress Modulates Instrumental Learning Performances in Horses (Equus caballus) in Interaction with Temperament. PLoS ONE 8(4): e62324. doi:10.1371/journal.pone.0062324
The full study can be accessed online at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0062324