Abstract: The present study investigated how stress affects instrumental learning performance in horses (Equus caballus) depending on the type of reinforcement. Horses were assigned to four groups (N = 15 per group); each group received training with negative or positive reinforcement in the presence or absence of stressors unrelated to the learning task. The instrumental learning task consisted of the horse entering one of two compartments at the appearance of a visual signal given by the experimenter. In the absence of stressors unrelated to the task, learning performance did not differ between negative and positive reinforcements. The presence of stressors unrelated to the task (exposure to novel and sudden stimuli) impaired learning performance. Interestingly, this learning deficit was smaller when the negative reinforcement was used. The negative reinforcement, considered as a stressor related to the task, could have counterbalanced the impact of the extrinsic stressor by focusing attention toward the learning task. In addition, learning performance appears to differ between certain dimensions of personality depending on the presence of stressors and the type of reinforcement. These results suggest that when negative reinforcement is used (i.e. stressor related to the task), the most fearful horses may be the best performers in the absence of stressors but the worst performers when stressors are present. On the contrary, when positive reinforcement is used, the most fearful horses appear to be consistently the worst performers, with and without exposure to stressors unrelated to the learning task. This study is the first to demonstrate in ungulates that stress affects learning performance differentially according to the type of reinforcement and in interaction with personality. It provides fundamental and applied perspectives in the understanding of the relationships between personality and training abilities.

Abstract: Temperament is an important factor when working with horses. Behavioral tests have been developed to measure certain dimensions in horses. Relations between temperament and ability to riding activity have been highlighted (Lansade 2008a). The aims of this study were 1) to evaluate the effect of age on temperament, 2) to verify that temperament are related to breeds 3) to check if the ease to be ridden is in relation with temperament, on a first set of data. Five dimensions of temperament have been measured in 98 field stallions (Table 1). They were tested as described by Lansade (2008 a,b): fearfulness/curiosity (tests: crossing a novel aera, suddenly opening an umbrella, novel object), gregariousness (test: isolation), locomotor activity (during the other tests), reactivity/curiosity to a non familiar human (tests: passive and active human), tactile (Von Frey filament) and auditory sensitivities. Table 1: Number of stallions according to breed (or group of breeds) and age. Breeds or groups of breeds Young (<13 years) Old (>=13 <20 years) Merens 1 15 10 Leasure horse breeds 2 13 10 Jumping pony breeds 3 / 20 Jumping horse breeds4 9 10 Arabians / 11 Total 37 61 (1) Merens : french mountain horse breed (2) Appaloosa, Barbe, Lusitanian, Polish, Paint (3) French Saddle Pony, Connemara, New Forest, Welsh (4) French Saddle Horse, Anglo-Arab, KWPN, Foreign breeds Effect of age. Due to imbalanced data, only stallions from 3 breed groups were compared (29 young ones selected at random and 30 old ones). Young stallions presented a higher emotivity (more elevated distance/intensity of the flight after umbrella opening (P=0.001)) and curiosity (more sniffings/nibblings the passive human (P=0.04) and the novel object (P<0.0001)) compared to old ones. Relation with breed groups. In young stallions, differences were noted : in the number of trots during social isolation (P=0.001) and in the tactile sensitivity (P=0.005). Merens had smaller values than Jumping horses for these 2 variables. In older stallions, differences were also noted: in the number of sniffings/nibblings the novel object (P=0.04), in the manner to cross the novel aera (P=0.03), in the distance and intensity of the flight after umbrella opening (P=0.04), in the number of trots during isolation (P=0.02) and in the tactile sensitivity (P=0.03). Merens had lower reactivity compared: 1) to Arabians (for novel aera) and 2) compared to Jumping ponies and Jumping horses (for isolation and tactile sensitivity). Minimal level of rider. Stallions of all ages and breeds were divided into 3 groups according to the level of riders able to ride them safely, according to a questionnaire: beginners, intermediate level and pre-national competition level. Stallions adapted to beginners showed lower values in the number of trots during isolation (P=0.02) and in the tactile sensitivity (P=0.03) than stallions rode by pre-competition level riders. Conclusion : The intensity of fear reactions to suddenness decreased with age. Differences between breeds and eases of use have been related to temperament measurements.