Animals Choosing their Music
Many places have let animals choose music to hear. A 2009 survey of 238 staff at 60 zoos worldwide found that 93% of staff think auditory enrichment is "Important" for mammals, but 74% never provide it, because of staff time constraints.
Studies vary on how much primates like music, and there are different ways to interpret the studies. The researchers did important work to help animals choose, but it is challenging. Humans gradually discover music we like over many years. We vary a lot, get suggestions from others, and we have private spaces to enjoy our choices without disturbing others. Most of us like some music and dislike some, even within a genre.
Responses of female rhesus macaques to an environmental enrichment apparatus
S. W. Line, A. S. Clarke, H. Markowitz, G. Ellman Laboratory Animals (1990) 24, 213-220
Line et al. mounted a radio on the cages of five single adult female rhesus macaques. The radio was available for a 14-week period and was preset to a soft rock music station; the animals could turn the radio on and off by touching two different bars. Individual animals turned on the radio for 0–24 hours on different days. Different animals averaged 3-15 hours per day over the experiment as a whole, with the overall average of the 5 animals greater than 12 hours per day. Authors graph the total hours played by each animal each week. The monkeys showed no signs of losing interest in listening to the music.
Chimpanzees Prefer African and Indian Music Over Silence
Morgan E. Mingle, Timothy M. Eppley, Matthew W. Campbell, Katie Hall, Victoria Horner, and Frans B. M. de Waal, Journal of Experimental Psychology: Animal Learning and Cognition
A 2014 study found that 16 chimpanzees in Georgia stayed close to the loudspeaker during irregular rhythms in some Akan music (Ghana) and Indian ragas more than Japanese taiko, which has regular rhythms like the western music used in Edinburgh. Each type of music was played 40 minutes on 3 different days. The first three days were controls, with a silent stereo, followed by 9 days of music in random order. The researchers suggested regular rhythms may be unpleasant, since chimpanzees use regular rhythms in dominance displays, "stomping, clapping, and banging objects".
Music as enrichment for Sumatran orangutans (Pongo abelii)
Sarah E. Ritvo and Suzanne E. MacDonald, Journal of Zoo and Aquarium Research 4(3) 2016
Toronto researchers chose 210 pieces of music, from among the most popular on iTunes as well as Tuvan throat singing, which is similar to orangutan long calls. They played the first 30 seconds of each to 3 orangutans (separately), and after each snippet, let the orangutan choose between a repeat, or 30 seconds of silence, by touching the coloured half of a touchscreen to repeat, or the grey half for silence. The 3 individuals chose to repeat snippet of music 8%, 37% and 48% of the time. They had no chance to hear the rest of the tune, or go back to a tune they liked a lot, as humans do.
It would be interesting to give humans the same opportunity, and see how often they ask for repeats, when listening to 30-second snippets of someone else's choice of 210 tunes. All 3 orangutans "consistently displayed behaviours associated with orangutan distress" throughout the touchscreen sessions, not unreasonably, given the frustrations of hearing 30 seconds of random music 1,100 times. They pressed grey (silence) more when especially stressed or distracted.
This 30-second approach may be an effective way to race through a lot of tunes to find some tunes each orangutan likes. Whichever tunes they do like, there are hundreds of similar ones which a service like Pandora or Slacker could offer, to see how many of those they like. The researchers did not find any consistency by genre, which is similar to humans, who may like some classical tunes, or jazz or rock or folk, but not others. Even people who say they "like classical music" often have preferences for romantic, baroque, opera, modern, etc.
Is music enriching for group-housed captive chimpanzees (Pan troglodytes)?
Wallace,et al, PLOS ONE, March 2017
Another group of researchers let chimpanzees in Edinburgh come and go from an area where they played either silence or a rotation of 7 classical tunes, or 7 pop/rock tunes, which were very familiar, having been played more than 50 times each in experiments in the previous two years. Chimpanzees varied widely in how long they stayed in the small outdoor area where music played:
The wide range of time may mean the chimpanzees varied this much in how long they wanted to hear these familiar tunes. On the other hand the chimpanzees who listened the longest to music, also stayed longest during silence. They may have liked the area or they may have hoped for the music to start again.
The researchers tried to train the chimpanzees to choose for themselves whether to have music or silence in the research area, by pressing symbols on a touchscreen. However researchers were not sure the chimpanzees understood what the symbols meant, since training only gave them 3-second bursts of music plus half a grape each time they pressed any symbol. The 3-second bursts and grapes may have squelched any intrinsic pleasure in the music.
Chimpanzees could press symbols to turn music on or off, or switch between classical and pop/rock, but could not pick individual tunes and could not select new music. The researchers had removed dynamic range from each tune, "by reducing the volume of loud passages and increasing the volume of quieter ones."
The symbols were always in different locations on the screen, and symbols in the final sessions were much smaller and squarer than they had been in training. Any symbol preference may be for its appearance (zig-zags, stripes, or bubbles), not for the 3-second snippets. If chimpanzees do not group genres as humans do they would not realize there was a pattern where zig-zags gave them classical music. After training, most button pressing was in the first session, when they would have expected grape rewards, as they had in training. The training and observations were in cold weather, January-April 2015, outdoors at the Edinburgh Zoo.
McDermott and Hauser:
Nonhuman primates prefer slow tempos but dislike music overall Cognition 104 (2007) 654–668
Are consonant intervals music to their ears? Spontaneous acoustic preferences in a nonhuman primate Cognition 94 (2004) B11–B21
The title of their 2007 article, "Nonhuman primates prefer slow tempos but dislike music overall", has been much quoted and has led trainers to avoid playing music to primates. However if monkeys can turn music on and off, all wanted music part of the time, even after a highly stressful introduction to a new small cage.
Cotton-top Tamarin and Common Marmoset monkeys used body location to trigger the researchers to change sound. Monkeys could see researchers, so could have received unconscious cues ('07, '04). Experiments were done with varying numbers of 3 to 8 animals.
Tamarins and Marmosets were measured when they were highly stressed. Researchers carried each animal to the entrance to a small cage with two branches, left the room, opened the cage remotely, and in the next 5 minutes the researcher played different sound depending which branch the animal was in. They do not say how the animals reacted to being carried to the cage, but "distress calls... screams [are] produced by [tamarins] being held by our veterinary staff during routine checkups" ('04 p.B15), and, "Primates dislike being handled and are stressed by it" (AWI '15 p.176) so carrying them would leave them highly distressed for the next 5 minutes, during the experiment.
Researchers do not say the cage size, but it appears about 25cm high. Tamarins average 23 cm, and Marmosets 19 cm, so they have little room, not "allowing the animals to move up to heights where they feel secure" (Medical Research Council (2004) of the United Kingdom, quoted in AWI '15 p.176).
An even more sophisticated system would add videos and/or games. Dr. Washburn's 2003 Presidential Address to the Southern Society for Philosophy and Psychology said,
Dolphins used "a movable lever ... at night to turn on or off or select among various tape-recorded acoustic stimuli, including dolphin sounds, whale sounds, human voices, music, etc." (Herman, Cetacean Behavior '80)
A captive Orca was observed to always want new tunes, and objected to repeats. Orcas are far more acoustically sophisticated than primates, but primates may have some preference for new tunes too, as humans do.
Java Sparrows triggered a photosensor by sitting on a particular perch, which determined which music was played. Two birds preferred Bach and Vivaldi over Schoenberg or silence. The other two birds had varying preferences among Bach, Schoenberg, white noise and silence. ('98)
Zebra Finches pecked levers to play music, sometimes for hours, then stopped for hours. It appears each lever played a short tune, which birds could and did repeat (no date).
Goldfish triggered Rite of Spring , Bach Toccata and Fugue in D Minor, or silence by presence in different thirds of a tank. The tank was painted white to limit visual stimuli, such as experimenters' body language. A camera and computer recorded fish location and played Bach if at one end, Stravinsky if at the other end, and silence when in the middle. Only one of the 6 tested showed a preference for one end, where Rite of Spring played. All spent about 2/3 of their time with music, 1/3 with silence, consistent with the music being in 2/3 of the tank. ('09)
The research projects here were staff intensive and gave limited times and choices of music, because of time constraints. It is worth thinking what some ideal systems might be, so research can see which work best for different animals: