Training pair-housed Rhesus macaques (Macaca mulatta) using a combination of negative and positive reinforcement

When training animals, time is sometimes a limiting factor hampering the use of positive reinforcement training (PRT) exclusively. The aim of this study was to evaluate the effects of a combination of negative and positive reinforcement training (NPRT). Twenty naïve female Rhesus macaques (Macaca mulatta) were trained in 30 sessions with either PRT (n = 8) or NPRT (n = 12) to respond to a signal, move into a selected cage section and accept confinement. In the NPRT-group a signal preceded the presentation of one or several novel, and thus aversive, stimuli. When the correct behaviour was performed, the novel stimulus was removed and treats were given. As the animal learned to perform the correct behaviour, the use of novel stimuli was decreased and finally phased out completely. None of the PRT-trained animals finished the task. Ten out of 12 monkeys in the NPRT-group succeeded to perform the task within the 30 training sessions, a significant difference from the PRT-group (p = 0.0007). A modified approach test showed no significant difference between the groups (p = 0.67) in how they reacted to the trainer. The results from this study suggest that carefully conducted NPRT can be an alternative training method to consider, especially when under a time constraint.