Grandin, T., Curtis, S. E., Greenough, W. T. 1988. Environmental enrichment for pigs: Differences in somatosensory cortical neurons and subsequent behaviour. Proceedings of the VIth International Congress on Animal Hygiene 2, 692-695.

Pigs raised in a windowless building with hanging rubber hose toys and weekly petting were less excitable compared to pigs raised with no extra environmental stimulation. Pigs exposed to an enriched environment approached novel objects more quickly than animals raised in a barren environment.