The pens were 6.1 × 5.6 m and located in an enclosed building thathad a 6.1 × 1.35 m area with a concrete floor and a 6.1 × 4.25 m unpavedfloor area. The four pens and feeders were aligned in a row adjacent toone another. The pens where Night and Day animals resided when notin pens with feeders were located adjacent to the corresponding feedingpen across a 3-m wide hallway used for animal and personnel movement.The sides of pens were metal mesh panels that allowed visual contactamong animals of different pens as well as aggressive behavior notedlater. Water was available in all pens via automated waterers and pineshavings were periodically added as bedding. Environmental conditionswere similar among the pens. Nonetheless, groups were moved to differ-ent pens and feeders every period, so that each group occupied three ofthe pens for one period and one pen in two periods (i.e., periods 1 and 5).