Music as enrichment for Sumatran orangutans (Pongo abelii)

Music is commonly employed as auditory enrichment in NHP facilities under the assumption that music is as enriching for NHPs as it is for humans (Hinds et al., 2007; Lutz & Novak, 2005). The purpose of this study was to assess the utility of music as NHP enrichment by exploring musical preference and discriminative ability in three Sumatran orangutans. In Experiment 1, orangutan preference for music vs. silence was tested. Following exposure to a sample of music belonging to one of seven musical genres, orangutans were given the choice via touchscreen to continue to listen to the music sample previously played or to listen to silence instead.  Results indicated that all three orangutans either preferred silence to music or were indifferent.  No preference for any one of the musical genres tested over others was found.  In Experiment 2, orangutans’ ability to discriminate music from scrambled music was assessed using a touchscreen-delivered standard delayed matching-to-sample (DMTS) task. Results indicated that none of the three orangutans could reliably discriminate ‘music’ from ‘scrambled music’.  Taken together, results strongly suggest that these orangutans did not experience the musical stimuli as reinforcing and that use of music as enrichment in captive NHP facilities may be more aversive than enriching for some species.