Research on long-term cognitive enrichment in farm animals has also been tested using domestic pigs. The experiment began by conditioning the pigs to respond to unique acoustic noises in order to receive their food. Once they knew their own sound, they would be summoned individually to the feeding area. In the next phase, the pigs were required to press a button in order to receive their food and the number of times they needed to press the button increased with time. The pigs in the experiment that performed the cognitive enrichment were significantly less aggressive than the control pigs, experienced positive physiological changes, and were less fearful and more exploratory in novel situations.