A Danish study has shown negative reinforcement to be beneficial in getting horses used to unfamiliar objects, but comes with a warning over stress responses in animals.
The results of the study by Janne Winther Christensen, of Aarhus University, have been published in the Equine Veterinary Journal.
Christensen said the ability of horses to habituate to novel objects influences safety in the horse-human relationship. However, the effectiveness of different ways of habituating horse had not been investigated in detail.
Christensen set about investigating whether horses showed increased stress responses when negatively reinforced to approach novel objects, compared to horses that were allowed to voluntarily explore the objects.
The research also set out to discover whether negative reinforcement aided object habituation.
Twenty-two 2 to 3 year old Danish Warmblood geldings were used in the study.
Half were negatively reinforced by a familiar human handler to approach a collection of novel objects in a test arena. The other half of the horses – the voluntary group – were individually released in the arena and were free to explore the objects.
On the next day, the horses were exposed to the objects again without a human to allow the rate of habituation to be investigated.
Behavioural and heart-rate responses were recorded during the study.
Christensen found that all horses in the voluntary group initially avoided the unknown objects, whereas the handler was able to get all negatively reinforced horses to approach and stand next to the objects within the first two-minute session.
The negatively reinforced horses had a significantly longer duration of alertness and a higher maximum heart rate in the first session. On the following day, however, the negatively reinforced horses spent significantly less time investigating the objects and approached a feed container, placed next to the objects, faster than the voluntary group, indicating increased habituation.
Christensen found that while the approach using negative reinforcement aided habituation in young horses to approach novel objects, there was an increased stress response during initial exposure.
“Although negatively reinforced approach appears beneficial for habituation, the procedure should be carefully managed due to increased stress responses in the horse which may constitute a safety risk,” Christensen said.
“Further experiments should aim to investigate differences in stimulus intensity.”
Object habituation in horses: The effect of voluntary vs. negatively reinforced approach to frightening stimuli.
Janne Winther Christensen