Person:

Krasnow, Max

Parent-offspring conflict, or the conflict over resources between parents and their children due to differences in genetic relatedness, is the biological foundation for a variety of psychological phenomena, including sibling rivalry and child abuse. This form of conflict is particularly relevant to the domain of parental investment: the provisioning of resources to offspring by parents and alloparents. The kinship theory of genomic imprinting is the primary evolutionary explanation for the occurrence of specialized genetic expression in chromosomal domains relevant to phenotypic expression of parent-offspring conflict. Specifically, complementary parental contributions in the same region of the genome promote opposing parental demand behaviors. This theory predicts that people with genomic imprinting disorders will show alterations in traits and behaviors related to parental investment. In this paper, we apply this prediction to the psychological resource of parental attention, for which vocalizations in general, and music in particular, may be an honest signal. Individuals with Prader-Willi syndrome show increased physiological responses to music listening consistent with a reduced demand for parental investment. Here we report the complementary pattern necessary to support the theory: we find that individuals with Angelman syndrome demonstrate a relatively reduced physiological response to music, consistent with an increased demand for parental investment. In addition to presenting evidence of the value of applying the kinship theory of genomic imprinting to psychological phenomena, these data provide a comprehensive test of the theory that at least one aspect of human musical psychology evolved to mediate conflict over attentional demands between parents and offspring.

We present a theory of the origin and evolution of infant-directed song, a form of music found in many cultures. After examining the ancestral ecology of parent-infant relations, we propose that infant-directed song arose in an evolutionary arms race between parents and infants, stemming from the dynamics of parent-offspring conflict. We describe testable predictions that follow from this theory, consider some existing evidence for them, and entertain the possibility that infant-directed song could form the basis for the development of other, more complex forms of music.

Why do people sing to babies? Human infants are relatively altricial and need their parents’ attention to survive. Infant-directed song may constitute a signal of that attention. In Prader-Willi syndrome (PWS), a rare disorder of genomic imprinting, genes from chromosome 15q11–q13 that are typically paternally expressed are unexpressed, which results in exaggeration of traits that reduce offspring’s investment demands on the mother. PWS may thus be associated with a distinctive musical phenotype. We report unusual responses to music in people with PWS. Subjects with PWS (N = 39) moved more during music listening, exhibited greater reductions in heart rate in response to music listening, and displayed a specific deficit in pitch-discrimination ability relative to typically developing adults and children (N = 589). Paternally expressed genes from 15q11–q13, which are unexpressed in PWS, may thus increase demands for music and enhance perceptual sensitivity to music. These results implicate genomic imprinting in the psychology of music, informing theories of music’s evolutionary history.