Table 2 Description of the behaviours observed in the video analysis of the strange person test (120 s)

Duration (in seconds) that the pig takes to approach the person, without necessarily touching the person. More precisely, the number of seconds that the pig spends from the beginning of the test to cross the line that divides the pen in the “area with the person” and the “area without the person”. The perpendicular line divided the pen in two parts (1.85 m/2 = 0.93 m): the part where the strange person sat down was named the “area with the person”, and the other part was named the “area without the person”. Longitudinally, the person sat on the floor and occupied 0.55 m, meaning that when the pig crossed the line with at least one leg, the person was 0.35 m from the pig (from the pig’s leg) and thus 0.10 m from the pig’s nose.

Duration (in seconds) that the pig spends in the “area without the person” (see explanation above).

Duration (in seconds) that the pig touches any part of the strange person’s body with the snout.

Frequency (number of times) that the strange person needs to move the pig away with his or her arm or leg, nicely but firmly, because the pig is biting the person hard.

Duration (in seconds) of tail swinging in any direction; the tail mostly was swinging from side to side, resulting in lateral tail movements [31, 34, 46].