| Experiment 1 |
| Looking at photograph |
Attentive with head orientated directly towards the photograph. |
| Approach |
Horse walks up to the photograph, bringing their nose to within 30 cm. If horses approached both photographs we recorded which they approached first. |
| Touch the photograph |
Horse touches the photograph with their nose. |
| Time spent in proximity to a photograph |
Testing area divided into quarters. Horses’ position measured from the time the first foreleg is placed into the quarter until the first foreleg leaves the quarter. |
| Experiment 2 |
| Looking at photograph |
Attentive with head orientated directly towards the photograph. |
| Gaze bias left/right |
Oriented to the stimuli (judged by at least one ear still oriented towards the photograph) but with the head turned to one side. Gaze bias left refers to a preference for viewing with the left eye (i.e. head turn right) and gaze bias right a preference for the right eye (head turn left). |
| Avoidance |
Horse moves away from the photograph with visible alarm, e.g. nostril flaring, wide eyes, tense muscles. |
| Approach |
Horse reaches their nose or moves their body forward towards the photograph. |
| Touch the photograph |
Horse touches the photograph with their nose. |
| Both ears forward |
The openings of both ears are facing forward of the midline. |
| Both ears back |
The openings of both ears are facing posteriorly of the midline. |
| Asymmetrical ears |
Left ear forward/right ear back |
The opening of the left ear is facing forward of the midline while the right ear opening is directed posteriorly. |
| Right ear forward/left ear back |
The opening of the right ear is facing forward of the midline while the left ear opening is directed posteriorly. |
