Epigenetics of Music: A Karaoke vs. Bach Genetic Conflict?

An epigenetic syndrome gives insights into the epigenesis of music appreciation.

Posted Jun 03, 2017

An important factor in being human is our ability to appreciate and make music. As the authors of a paper soon to appear in Psychological Science point out:

Music is a ubiquitous part of human culture that predates our recorded history. Musical instruments rank among our most ancient artifacts, with bone flutes excavated in Germany estimated to be about 40,000 years old. The human auditory system is an order of magnitude older and our vocal production system is similar to those of many other mammals. It is thus likely that vocal music long preceded instrumental music, as Darwin and Helmholtz speculated; while songs leave no fossils, they appear in many small-scale societies, with remarkable diversity.

Whereas humans of all ages produce and enjoy music, a peculiarity of the music faculty is its omnipresence in infancy. Infants have robust music perception abilities and parents often sing to their infants and children in a stereotyped style. Consistent with predictions that this behavior is a human universal, anthropologists have documented infant-directed song across many cultures.

The authors go on to speculate that care-givers have evolved their tendency to sing to babies as a signal of attention to infants, driven by the dynamics of parent-offspring conflict. In this study, they tested a key prediction of that theory: that responses to music and music perception abilities should be atypical in populations with disorders of genomic imprinting.

As I have explained in previous posts, imprinted genes are expressed from only one parent’s copy, and theory predicts that those expressed from the father’s copy should generally demand more investment from the mother to the benefit of the father’s genes already invested in the offspring, while those from the mother should generally counter such demands in the interests of herself and her future offspring, given that she alone provides all the resources for the offspring’s growth and development during pregnancy and lactation.

Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science
Figure 1. Absence of paternally-expressed genes in Prader-Willi syndrome. A typical chromosome 15q11–q13 is depicted in a, for comparison to the three forms of PWS: b,deletion of the paternal 15q11–q13 in approximately 65-75% of cases; c, maternal uniparental disomy in approximately 20-30% of cases; and d, imprinting center defects, random mutations, or unspecified genetic causes in remaining cases. Black regions denote unimprinted genes, blue regions denote paternally-expressed genes, pink regions denote maternally-expressed genes, and circles denote imprinting centers.
Source: Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science

And as I have also explained in a recent post, Prader-Willi syndrome (PWS) is the result of skewed expression of a run of important imprinted genes on chromosome 15 in favor of the mother (left). By contrast to Angelman syndrome children, who show the opposite, paternal pattern of expression and are hyperactive, sleepless, frequently crying prolonged sucklers (every mother’s worst fear!), PWS babies are inactive, sleepy, weak crying, poor sucklers.

On this theory, the musical phenotype of people with PWS should differ from that of typically developing people in a fashion consistent with reduced demand for attentional investment. Reduced demand for attentional investment could manifest itself in one of two ways. First, increased potency of engagement with music and response to music could enable parents to invest relatively less for the same degree of effect on infants. Second, reduced demand for attention could translate to an overall reduction in musical interest, thereby producing a reduced demand for music. The present experiments test these hypotheses against each other, and against a null hypothesis where response to music in PWS is comparable to typically developing people.

The study aimed to characterize the musical phenotype in PWS by measuring three variables: (1) engagement response (increased motion) during music listening, (2) relaxation response (reduced heart rate) following music listening, and (3) pitch perception ability (tone-deafness).

On the first hypothesis, people with PWS are expected to engage more with music, relative to typically developing controls, and with effects limited to music (not in response to other pleasant, vocally-produced auditory stimuli). On the second hypothesis, people with PWS are expected to engage less with music, relative to the same controls and comparisons. On both hypotheses, people with PWS are expected to relax more following music listening (but not following other auditory stimuli) than typically developing controls. Finally, a deficit in pitch perception is consistent with both hypotheses, for two different reasons: respectively, because reduced discrimination between pitches might produce less choosy listeners, reducing demand for high-quality singing; or because impaired pitch perception might reduce interest in music in general.

Thirty-nine people with PWS (12 female, age in years: M = 28.2, SD = 10.1, range: 13.7–45.7) were compared to several cohorts totaling 589 of typically developing children and adults.

Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science
Figure 2. Increased motion during music listening in PWS. Motion was characterized by measuring the change in total graph-based visual saliency over time. a, Each frame of a video from each participant's listening session was converted to a saliency map, depicted in b, where each pixel has a saliency value of 0 (black) to 1 (white). Videos were processed at10Hz, and we computed the absolute difference between the sum of each frame's total saliency and that of the previous frame. These values were normalized to the 10 s period prior to the stimulus presentation; thus, larger values indicate more motion. c, Detected motion of the participant in a, who has PWS, while listening to a lullaby, are plotted (in red) against a typical typically-developing participant (in blue), listening to the same song. d, People with PWS move more than typically-developing people during music listening but e, not during speech listening. The violin plots depict kernel density estimations of the normalized motion values, averaged by participant; the vertical lines indicate the group means; in the box plots, the vertical lines depict the group medians and the boxes indicate the interquartile range.
Source: Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science

As the results diagrammed above illustrate, PWS subjects showed increased engagement (more motion) during music listening and increased relaxation (lower heart rate) after music listening, and reduced pitch perception ability, as diagrammed below left, confirming a key prediction from the authors’ theory of the evolution of infant-directed song.

Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science
Figure 3. Increased relaxation response after music listening in PWS. Heart rate values were normalized to the 10 s prior to each trial, as in the motion analyses; lower values thus indicate larger reductions in heart rate as a result of music listening. a, People with PWS have lower heart rate than typically developing people after music listening but b, not after speech listening. The violin plots depict kernel density estimations of the normalized motion values, averaged by participant; the vertical lines indicate the group means; in the box plots, the vertical lines depict the group medians and the boxes indicate the interquartile range.
Source: Samuel A. Mehr et al. (In press) “Genomic imprinting is implicated in the psychology of music,” Psychological Science

The authors argue that

Engagement and relaxation effects are interpretable as traits that decrease demand for music, such that the same amount of song produces larger effects in PWS than in typically-developing participants. Reduced pitch perception ability has a more speculative interpretation: infants with less sensitivity to pitch may be less choosy about the quality of the singing required to elicit a calming response, further reducing demands for parental investment. Together, these effects implicate intragenomic conflict in the psychology of music.

Not to mention Karaoke. Amar Annus, who kindly brought this study to my attention, tells me that he

could not help but recall the times when I worked in Finland and saw how popular karaoke is there. I am a self-taught musician, but I can sing and play guitar fairly well. Therefore I am not tolerant of very bad and out of the tune singing, but many Finns seemed greatly to enjoy long nights with excessive low quality and loud singing. I could not understand the pro-social feelings of warmth and cosiness that such parties generated in Finnish culture, but now appreciation of bad singing may be explained by excessive in-group tolerances.

Is Karaoke another shadow on the dark side of oxytocin? Mothers' equal genetic investment in all their offspring certainly gives their genes an interest in in-group tolerance which the Mother's baby: Father's? Maybe! effect does not give fathers.

Talking of which, the authors add that their findings imply that paternally-expressed genes from this region of chromosome 15 which are not expressed in PWS may work in a diametrically opposite way: enhancing liking for music and increasing sensitivity to it. Indeed, I might add that the fact that perfect pitch is much more common in autistics than in the rest of the population, and that innate musical ability is one of the most common and most striking gifts seen in autistic savants supports this supposition. Furthermore, the oppositely imprinted syndrome to PWS, Angelman, tends to go with autism spectrum disorders and PWS (especially in the case where both copies of chromosome 15 are inherited from the mother) with high risk of psychotic spectrum disorders, just as the imprinted brain theory proposes.

So, if we can blame maternal epigenetics for Karaoke, can we credit paternally expressed genes for Bach? After all, Bach is associated with complex contrapuntal and choral music: the Cantatas, Passions, and Art of Fugue. Crucially, choral singing demands singing in tune, just as the clavier has to be well tempered to ensure that the complex mechanism of a fugue works at all. Indeed, could this be why, even though Karaoke is a Japanese word, some of the best Bach comes from Japan?

(With Thanks to Sam Mehr and Amar Annus for their help.)

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