Monkeys Enjoy Music - Chimpanzee Music Preference

Chimpanzee Music Preference

Jordan Denos

California State University Fullerton

Introduction

        Music has always been a source of joy for humans. Every individual human has their own preference for what kind of music they enjoy. Since we are largely genetically similar to chimpanzees it would be safe to argue that they as well have a preference for certain types of music. A study conducted by Mingle et al. (2014) argued that chimpanzees prefer African and Indian music over silence, while having no preference for Japanese music. It has been shown before that nonhuman primates “consistently prefer silence to the type of music that was tested” (McDermott & Hauser, 2004-2007; Sugimoto et al., 2010; Tincoff et al., 2005) as well as showing that chimpanzees show an increase in social behavior and a decrease in agonism when music is played (Howell, Schwandt, Fritz, Roeder, & Nelson, 2003).  The main motivation for the study was to compare nonhuman and human primate’s behavioral responses to different auditory structures. This study is interesting in that human and nonhuman primates are similar and understanding more about chimpanzees and other nonhuman primates can give us a better knowledge of ourselves.

Method

        The study consisted of 16 adult chimpanzees that were housed in two groups (Group 1 and Group 2). Group 1 consisted of one male and 10 female chimpanzees, and Group 2 consisted of three males and nine female chimpanzees. The chimpanzees were housed in a research center in Lawrenceville, Georgia. The chimpanzees lived in spacious outdoor enclosures with toys, grass and climbing materials. Most of the subjects were frequent participants in other research studies. Although some of the chimpanzees had previous experience with Western music, they did not have any experience with World music. The researchers chose West African akan, North Indian raga, and Japanese taiko instrumental music as the acoustic stimulus. The researchers played each audio stimulus for 40 minutes consistently. They chose these because they employ contrasting acoustic characteristics and are representative of their region of origin. They also chose these styles because of a maintained base tempo of 90 beats per minute, which human infants and other marmosets have shown a preference for (Mcdermott & Hauser, 2007).  All music was played at 50 dB so that all music was the same average amplitude. An enclosure was divided into four zones extending from the audio stimulus. Zones were labeled 1 through 4 with 1 being closest to the stimulus and 4 being the furthest. The study began at 8:30 a.m. with a researcher pushing play on the audio stimulus and then leaving the area immediately. Another researcher would be observing the locations of each chimpanzee in relation to the audio stimulus. The researchers would then take note of where the subjects where every 2 minutes until the end of the 40 minute period totaling in 21 scan samples.  Initial control trials were conducted over three consecutive days, followed by nine consecutive experimental trials. The order of the stimulus was randomized in each experimental trial. During some trials some of the chimpanzees failed to leave the indoor living area. Because of this trials were only conducted as long as 60% of the chimpanzees were present. Finally a proximity index was calculated for each subject and condition.

Results

        Researchers conducted a one-way analysis of variance that showed that the two chimpanzee groups did not statistically differ. Because of this the data was combined for both groups for all analyses. After combining the two groups a repeated measures ANOVA was conducted to compare the mean proximity index of all the audio stimulus for Zone 1. Post hoc protected Fisher’s least significant difference tests were conducted to compare specific audio stimuli. Chimpanzees exhibited a preference for Zone 1 with the Indian raga and the African akan when compared with the control condition. The chimpanzees did not display a preference for the Japanese music. Furthermore an ANOVA was used to compare proximity indexes for each day to test for an effect of novelty. This showed no significant change in location preference throughout the trial days. One additional repeated measure ANOVA was conducted to determine variations in location preference during each trial. Finally the 40 minute period was divided into four 10 minute sections for analysis. These results showed no significant change in preference for location during each trial.

Discussion

        The authors came to multiple conclusions during this study. After exposing the chimpanzees to all three different music styles there was a clear preference to be closer to Indian and African music rather than silence. These results were stable throughout the whole experiment period which suggested that it was not just caused by a stimulus novelty. The preference for any type of music is in disagreement with previous studies done on Western music. When comparing this experiment to previous ones, the current study focused on world music whereas previous studies focused on western music. Further research shows that the sound of the Japanese music might be perceived as threatening because chimpanzee’s dominance displays commonly incorporate similar rhythmic sounds. The researchers did not compare their results to previous studies because they did not incorporate any Western music in their study and did not want any bias results. The researchers in the current study also used a different method of playback than previous studies and considered that it is theoretically possible that chimpanzees could prefer Western music if tested with their style of playback. The authors results show potential to investigate origin of music in humans from homologies in acoustic preference between nonhuman and human primates.