Fear is generally considered to be an undesirable emotional state that may reduce welfare, growth and reproductive performance in animals. Fear in horses is additionally problematic, because fear reactions can cause serious injury to both horse and human. Horses are primarily used for sports and leisure for a large number of children and young women. Unfortunately, horse riding ranks as one of the most dangerous sports in terms of the number and seriousness of accidents, and the ability of a horse to habituate to a range of otherwise frightening stimuli greatly increases safety in the horse-human relationship. However, there is a lack of research on fear reactions and no published research on basic habituation processes in horses. This licentiate project aimed to investigate the types of fear responses horses show towards novel stimuli acting on different senses, and to study how horses learn to be confident with an otherwise frightening stimulus using classical learning theory techniques. The experiments were conducted on two different groups of naïve stallions (n=24 and n=27). The first experiment showed that horses responded differently towards an olfactory stimulus compared to auditory and visual stimuli. The heart rate responses correlated between tests and probably reflected a non-differentiated activation of the sympathetic nervous system, while the behavioural responses were linked to the type of stimulus. The second experiment showed that gradual habituation was the most effective training method for horses to learn to react calmly to an otherwise frightening stimulus, compared to classic habituation and associative learning. Heart rate data revealed that horses may show physiological responses even when their behavioural response towards the stimulus has ceased. Choice of training method is likely to be especially important for the most fearful horses
