Table 2. Description of the behaviors performed by the horses once entered in the “mirror area”.
Attention to and exploration of the mirror, looking behind the mirror and mouth movements were collected under Open (OM) and Covered Mirror (CM) conditions; Scraping events were collected under the four experimental conditions (OM, CM, SHAM and MARK). Videos are provided in Supporting Materials showing the horses performing such behaviors.
| Description | Data collected | Supporting information |
|---|---|---|
| Attention to the mirror (FRONT) | ||
| The head of the tested horse had to be in the mirror area with one or both eyes visible in the reflected image for at least 3 seconds. | The time (secs) spent performing FRONT (state behavior) |
S1 Video S2 Video |
| Exploration of the mirror (EXP)* | ||
| The behavior EXP included the time (secs) spent by the tested horse sniffing, licking and touching the mirror with the mouth. | The time (secs) spent performing EXP (state behavior) | S3 Video |
| Looking behind the mirror (LOOK) | ||
| When the horse was close to the mirror (<1m) and put its head and neck forward the fence. We classified the behavior as a LOOK event only when the horse turned its head toward the rear side of the mirror thus using its visual binocular field. | The number of times the horse performs LOOK behavior (event behavior) | S4 Video |
| Movements of the mouth (MOUTH) | ||
| The behavior MOUTH included each mouth opening and tongue protrusion only when these behaviors were performed in FRONT of the mirror | The number of times the horse performs MOUTH behavior (event behavior) | S5 Video |
| Scraping (SCRA) | ||
| The horse rubbed the lateral side of its head (area between the labial and the caudal part of the mandibular branch) with both the ipsi- and contra-lateral forelimb. Other self-directed behaviors performed towards the muzzle or the ears were excluded. Moreover, during the SCRA event the horse could also rub the lateral side of its head against the surface of a fence. | The number of times the horse performs SCRA behavior (event behavior). Two SCRA events were considered as distinct when the horse separated its head from the paw or from the fence. |
S1 Fig S6 Video S7 Video |
* Sniffing, licking and touching were included in a single behavioral category as it is not possible to keep the different sensory modalities separated (e.g., licking includes both touching and sniffing)