“Exploring pigs’ (Sus scrofa domesticus) use of spatial and numerical cues in an ordinal task”

Numerical cognition and ordinal processing have been widely investigated in primates, birds, insects, and other taxa, whereas comparatively little is known about these abilities in ungulates, particularly domestic pigs (Sus scrofa domesticus). A previous study showed that pigs could identify the 2nd or 5th bowl in a series of six identical bowls using fixed inter-bowl distances. However, when spatial and numerical cues no longer coincided, pigs relied primarily on spatial cues. What remains unclear is whether pigs can learn to rely on numerical cues alone when spatial cues are unreliable already during training. In the present thesis, a total of 30 pigs were trained to locate food in either the 2nd or the 5th bowl in a series of six identical bowls. To investigate whether pigs can learn to rely on ordinal position alone, the inter-bowl distances were systematically manipulated throughout training. As the task proved highly demanding, only 1 pig met the predefined training criterion; additional training criteria allowed 9 more pigs to participate in the test phase, resulting in a total of 10 tested individuals. Pigs were tested in both a Sagittal condition, matching the training orientation, and a novel Fronto-Parallel condition, with varying inter-bowl distances in each test. Preliminary findings suggest that, although some pigs were able to achieve high success rates in the ordinal task even without spatial cues, substantially longer training might be required to reach higher group-level performance. While these results highlight the predominant, but not exclusive, role of spatial information in domestic pigs’ performance, we also cannot exclude the possibility that part of this pattern reflects an imprecise sense of ordinal position.