Fig. 1.

Schematic representation of the experimental set-up. a T-Maze task. The apparatus was fitted in a room (416.5 × 482.6 cm) with slatted concrete floor and grey walls. Black rubber mats were placed under the apparatus to prevent pigs from getting cold. The arm opposite to the assigned start arm was blocked with the guillotine door. b Spontaneous Object Recognition Test pen design. The pen (210 × 195 cm) was situated in an isolated room which contained six identical pens, one of which was the hold pen (two pens apart, on the left-hand side). The two objects were hung approximately 0.15 m above the ground, to be in the pig line of sight. The feeder was empty to avoid distraction. Blue star shapes in the hold pen represent enrichment objects