Individual Variation in Perception and Evolutionary Aesthetics: Grant Allen's 1878 Investigation of Congenital Amusia

The consideration of human evolution and variation were live topics in the second half of the 19th century. These issues converged in Grant Allen's (1848-1899) 1878 investigation of a case of "note-deafness" (i.e., tone-deafness; congenital amusia). This represents an early and overlooked example of experimental research into a selective perceptual deficit in an otherwise typically developing person. Allen employed objective tests to determine that the participant could hear but not accurately discriminate between pitches, while demonstrating preserved auditory perception of timing and intensity. He documented the participant's exposure, motivation, and training opportunities, and evidence of poor musical ability in family members. Parallel aspects of music and speech were investigated in perception and expression, and the neurological source of these difficulties was considered. These elements are hallmarks of high procedural rigor. Allen made connections between this music processing difficulty and his broader interests in the evolutionary physiology of aesthetics. Although Allen's study began to be cited in the 21st century, it has received little detailed consideration. This article examines the context and motivation for Allen's work and subsequent developments in the understanding of individual differences in sensory perception and processing. The interrelation between physiological variation and cultural practices that informed Allen's research questions regarding this selective perceptual impairment continue to figure in our view of congenital amusia and other individual differences. This article examines Allen's research questions as formulated in the late 19th century and those that remain unresolved in the understanding of human variation in perceptual processing.