A quarter of the 16 horses used in a German study proved to be innovative in their problem-solving, researchers report.
The findings point to the possibility that the most successful horses in the study were not necessarily born smart, but developed their abilities through exposure to enriched environments.
Domesticated horses are constantly confronted with novel tasks, Laureen Esch and her colleagues noted in the open-access journal Animals.
“However, innovative behavior in horses has not previously been investigated under experimental conditions.”
In their study, Esch and her fellow researchers investigated whether 16 horses found an innovative solution when confronted with a new feeder.
They went further, exploring whether the innovative behavior seen may have been affected by factors such as age, sex, size, laterality, fecal stress hormone concentrations, and task-related behavior.
The horses had never struck the feeder design before. It comprised a large hollow tube in which 3kg of feed was placed. Fitted inside the lower part of the feeder was a rod that protruded out the bottom. Each time the horse rotated the rod, a small amount of feed fell into the feeding trough below.
Each horse had 38 hours to work out how the feeder worked, and to empty it.
Four of the 16 horses emptied the feeder completely, to be classified as innovative problem-solvers.
An additional six horses (37.5%) solved the mechanism of the feeder by chance but consumed only some feed. They were classified as chance problem-solvers.
The remaining six horses did not manage to get feed from the feeder and were termed non-problem-solvers.
The horses’ age and their fecal stress hormone concentrations on the test day did not influence the innovative problem-solving ability and could be excluded as a factor.
Size also had no significant influence on whether horses solved the problem innovatively.
Of the 16 test horses, 10 showed a left motor laterality, two showed right motor laterality, and four showed no significant preference.
Although, statistically, motor and sensory laterality had no significant influence on the propensity to behave innovatively, all the four innovative problem-solvers showed a significant left-motor preference.
Two of the fully successfully problems-solvers were male and two were female, whereas four of the six horses who solved the problem by chance were males.
The study team said the 25% success rate seen among the horses was comparable to ratios of innovation seen in wild vervet monkeys.
“We found that innovative horses were more active while being tested, which is supported by a study in which horses with higher activity performed better in an acquisition task, than horses with lower activity.
“The innovative and by-chance problem-solver horses had a higher tenacity to solve the problem, than non-problem-solver horses,” they said.
“This is also supported by studies which demonstrated that animals that explore more slowly had higher problem-solving abilities.
“However, a greater tenacity for problem-solving may prevent success if individuals cannot inhibit making errors.
“Our findings call for further studies on a larger number of animals to investigate whether differences in task-related behavior may be the key to understanding innovative problem-solving in horses.”
The study team found that the innovative and by-chance problem-solving horses in the study had elevated baseline values of fecal stress hormone concentrations.
This, they said, which may be the result of repeated stimulations in enriched environments.
“Hence, the individuals’ life history may affect the individuals’ problem-solving abilities,” they suggested.
“Individuals’ early life experience may also explain the motor left side bias of the innovative problem solvers and sensory left side bias of three-quarters of the innovative problem-solver horses.
“Early experiences may have affected the development of hemispheric specialization and resulted in an emotional, right hemispheric (that is, left motor and sensory sided) cognitive bias.”
This, they said, is supported by the finding that left-handed marmosets showed higher concentrations of the stress hormone cortisol than right-handed marmosets.
“In summary, the innovative and by chance problem-solvers’ elevated baseline [fecal stress hormone] concentrations and the innovative problem-solvers’ preference for the left eye and forelimb may indicate that innovativeness in horses is associated with emotionality.
“The quality of the emotionality may be positive or negative, as there is evidence for horses preferring sensory organs of the left side for the intake of positive and negative emotional information.
“The feeder, a food-related novel object, may provoke either positive or negative emotional reactions and the motor and sensory left lateralized innovative horses may have had more brain power available for solving this innovation task.”
The tendency of geldings to be more innovative may be explained by differences in behavior and learning capacities, as male horses exhibit more play behavior and are considered to learn more quickly, than mares.
“A follow-up study is needed to clarify whether sex is decisive for innovative behavior in horses.”
Interestingly, the innovative horses took more time to approach the feeder. This may have been a result of their higher inhibitory control or may suggest that some horses solved the problem through reasoning, and therefore through higher cognitive abilities.
“We consider that innovative problem-solving abilities in horses may be mediated by inherent behavioral differences and former experiences in the individuals’ life. Environmental enrichment through improved keeping conditions may contribute to the mental welfare in horses.”
The full study team comprised Esch, Caroline Wöhr and Michael Erhard, all with Ludwig Maximilian University Munich, and Konstanze Krüger, with Nuertingen-Geislingen University.
Esch, L.; Wöhr, C.; Erhard, M.; Krüger, K. Horses’ (Equus Caballus) Laterality, Stress Hormones, and Task Related Behavior in Innovative Problem-Solving. Animals 2019, 9, 265.