A thirteenth-century theory of speech

This paper explores and responds to a historical theory pertaining to the psychology and physiology of speech. This theory was developed in the early thirteenth century, but within it may be found many of the same considerations as those of modern neuroscience—the nature of mental representations, the relationship between those representations and external stimuli, and correspondences between the sensory faculties. Examining this theory, from such a contrasting intellectual context to our own, raises questions of the role of experimentation, observation, and modelling, and what constitutes permissible evidence for supporting or rejecting hypotheses. Robert Grosseteste (c.1175–1253) was a celebrated medieval thinker, who, as well as writing on philosophy and theology, developed an impressive corpus of treatises on the natural world. Here, we analyze one of these treatises—his text on sound and phonetics: De generatione sonorum (On the Generation of Sounds)(DGS). The DGS was probably written in the first decade of the thirteenth century, several centuries before the apparent “scientific revolution” in Early Modern Europe. It was a formative period, however, for the development of European scientific thought, during which the reception of Greek natural philosophy, enabled by their transmission, translations, and commentary from Arabic and Greek into Latin, prompted new conceptual frameworks for the consideration of natural phenomena.1–3 For modern science, reading medieval works presents several significant challenges, starting not least with that of editions and translations. This analysis of the DGS has only been possible through interdisciplinary
collaboration between science and humanities scholars, resulting in the compilation of a new critical edition and translation of the text.4,5 Previous interdisciplinary research has already explored other scientific treatises written by Grosseteste: the De colore (On Colour),6 De iride (On the Rainbow),7,8 and De luce (On Light).9 In the De colore, Grosseteste develops a pioneering application of mathematics to psychology. Within the space of approximately 400 words, he claims that colour occupies a continuous, threedimensional space, contrary to the prevailing one-dimensional theory of the time.6 It is surprising to find this theory articulated six centuries before threecolour printing techniques were established10 and trichomacy was formulated by Thomas Young.11 In the DGS, the treatise we explore and respond to in this paper, Grosseteste attempts a similarly mathematical, combinatorial abstraction for phonetics—specifically for vowels—as he attempts for colour. Several features of how he goes about doing this are of interest to the modern reader. Whereas Grosseteste’s colour space is explicitly continuous, the vowel space described in the DGS is explicitly categorical. Underpinning his theory is a multimodal framework identifying correspondences between the mental representation of vowels, their physical production, their perception, and their external representation as letter shapes. Within this framework, the correspondences between speech perception, letter perception, and shape perception, have particular modern resonances in audiovisual speech and involvement of the motor system during speech perception. In the second half of this paper, we present an experimental interpretation of the text, using artificial vowel synthesis and psychophysics to test the claims of correspondence between abstract, geometric acoustic chamber shapes and vowel perception. Before presenting a detailed discussion of the DGS, a question that might first be addressed is why one ought to concern themselves with medieval science. Modern neuroscience is already at an interdisciplinary juncture between psychology, physiology, biology, and mathematics; why should matters be further complicated with the inclusion of medieval history and Latin? An answer may be found in the sheer wealth of scientific theory and observation that was amassed during this period, which largely remains untapped. The history of science is highly non-linear, despite its frequently linear presentation, leaving worthwhile questions and suggestions unresolved in every historical age.12 Psychological phenomena such as the perception of speech are not new, and have been prompting rational discourse throughout many historical and geographical cultures. By engaging with these theories today, we may find unexpected agreement with, or perspectives that are strikingly different to, our own. In either case, we stand to gain much from the exercise.