Tactile perception is involved in a variety of contexts (adaptations to climatic conditions, protection of the body against external dangers...) and is as important as the other sensory modalities for the survival of an individual.This tactile modality has been particularly well studied in humans, revealing high individual variations modulated by a variety of intrinsic and extrinsic factors such as age, sex, pathological disorders or temperament.Tactility is also involved in animals' social lives, although there are disparities between species. For example, social tactile contact among horses is limited, but this does not mean that they do not react to tactile stimuli but rather with their very thin skin they are able to detect minute stimuli (although they respond more to larger stimuli). Despite a fairly large effort to characterize it, there are controversies concerning equine tactile sensitivity.In this review, we examine studies that have used the same tool (Von Frey filaments) and try to disentangle what could explain the differences observed. It appears that many aspects are poorly known or controversial and that the procedures may be so different that the results of different studies cannot be compared. We went further by testing tactile reactivity of a population of unridden horses and found that four factors influenced their tactile reactivity (type of horse, filament size, body area, time of day). These results could explain some of the discrepancies observed in the literature and suggest, in particular, that more attention should be paid to the context of the test. Keywords: perception, equids, Von Frey filaments, methodology force. This principle therefore allows a known, measurable and reproducible force to be applied to the skin surface.Von Frey filaments were initially developed for humans to define tactile perception thresholds (Bell-Krotoski et al. 1995). A nylon filament delivering an average force of 0.07g was found to be a good predictor of the "normal" pressure threshold of light touch on hands and on a large part of the body of adult humans (Bell-Krotoski et al. 1995). This tool has become widely used both for human, i.e. medicine (Jerosch-Herold 2005) and preclinical neuroscience (Le Bars et al. 2001), often to assess pain with the hope of therapeutic translation (Mogil 2009) but also for animal (

Tactile perception in humans varies between individuals and could depend on extrinsic factors such as working activity. In animals, there is no study relating the influence of animals’ work and their tactile reactivity per se. We investigated horses’ tactile reactivity using von Frey filament in different body areas and compared horses working only in equine-assisted interventions (EAI), in riding school (RS) lessons, and in both activities (EAI-RS). We further compared tactile actions by people with or without mental and/or developmental disorders during brushing sessions. The results indicated that EAI horses showed higher tactile reactivity compared to EAI-RS and RS horses, both in terms of number of reactions overall, and especially when the test involved thin filaments. All horses showed high tactile reactivity when tested on the stifle, and this was particularly true for EAI horses. These differences could be related to humans’ actions, as participants diagnosed with disorders brushed more the hindquarters and showed more fragmented actions. This study opens new lines of thought on the influence of EAI working activity on horses’ tactile reactivity, and hence, on horses’ sensory perception. Tactile reactivity outside work, may be directly (via tactile stimulations) or indirectly (via the welfare state), influenced by working conditions.