Not just the alveolar trill, but all “r-like” sounds are associated with roughness across languages, pointing to a more general link between sound and touch

Rémi Anselme, François Pellegrino, Dan Dediu

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Rémi Anselme, François Pellegrino, Dan Dediu. Not just the alveolar trill, but all “r-like” sounds are associated with roughness across languages, pointing to a more general link between sound and touch. Scientific Reports, 2025, 15 (1), pp.12930. 10.1038/s41598-025-94850-0. hal-05532858

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# Not just the alveolar trill, but all “r-like” sounds are associated with roughness across languages, pointing to a more general link between sound and touch

Rémi Anselme<fnref n="1" />, François Pellegrino<fnref n="1" /> & Dan Dediu²,³,⁴✉

ARISING FROM: B. Winter et al.; Scientific Reports https://doi.org/10.1038/s41598-021-04311-7 (2022).

In a recent and fascinating paper, Winter and colleagues<fnref n="1" /> (henceforth WSPD) argue that languages with the alveolar trill [r] (henceforth trill) in their sound inventory tend to overrepresent “r” sounds in the words whose meaning is linked to the tactile sensation of “roughness”. Compiling data on hundreds of languages, they therefore postulate a cross-modal association between physical touch and the acoustic characteristics of the trill sound. Critically, their claim hinges on the data and the process used to decide whether a given language has a trill in its sound inventory. Perhaps surprisingly, this decision is far from trivial because, in language descriptions, the trill symbol [r] tends to represent a generic “r-like” sound (i.e. a rhotic) rather than the specific acoustic trill.²,³ We show here, using a more principled coding and checking procedure, and an extended statistical reanalysis, that “r-like” sounds in general—and not just trills—are associated with “roughness”. Therefore, we confirm the existence of a tactile-speech association, but a more general one than that postulated by WSPD. A different explanatory framework is therefore required, drawing for instance on wider sound symbolic properties of “r-like” sounds irrespective of their diverse acoustic properties, or to diachronic or cognitive processes that retain these associations despite a limited frequency of actual trills.

WSPD coded whether a language has the trill /r/ in its phonological inventory based on PHOIBLE⁴, a database containing phonological inventories for several thousand languages (and allophones for a subset thereof), and their own “phonetic judgments based on existing reports and reference grammars”. In some cases, they also relied on additional online resources (see their supplementary materials available at https://osf.io/6nma2/). WSPD “took a conservative approach” whereby each language falls into one on the following categories: “trilled /r/” if it has “a single trilled rhotic or multiple contrastive trilled rhotics”, “other” if it has a single “non-trilled rhotic” or multiple contrastive non-trilled rhotics; all other cases were excluded from the analysis.

This decision was mainly informed by the presence of the *grapheme “r”* among the symbols used to describe a language's sound inventory since it is supposed to stand for the phoneme /r/, which is in turn considered as mainly produced as an acoustic trill. While this kind of implication chain is valid for most phonemes (e.g. the grapheme “t” in the English sound inventory transcribes the phoneme /t/ which, in turn, can be produced as a prototypical unaspirated dental stop, among other allophones), it turns out to be weak for rhotics in general and /r/ in particular. The grapheme “r” is unfortunately a poor proxy for the presence of the actual trill in a language because this symbol tends to represent a generic “r-like” phoneme, as thoroughly explained elsewhere. This problematic situation arose from the “fluid” definitions of rhotics⁵, the difficulty in phonetically defining trills, in distinguishing a trill [r] from a tap [r], and a confused history of guidelines for identifying and transcribing it³. As a consequence, as WSPD are fully aware, the acoustical properties of an “r-like” sound cannot be reliably assumed from the presence of the grapheme “r” in the language inventory alone.

Therefore, we comprehensively recoded the languages used by WSPD. The additional data sources and coding decisions per language are given in the Supplementary materials, starting from the references in the *Glottolog*⁶ for each language (see also ref² Chapter 5). These additional resources include grammars and grammar sketches

<footnote n="1">¹Laboratoire Dynamique du Langage, UMR 5596, Université Lyon2-CNRS, Lyon, France. ²Department of Catalan Philology and General Linguistics, University of Barcelona, Barcelona, Spain. ³University of Barcelona Institute for Complex Systems (UBICS), Barcelona, Spain. ⁴Catalan Institute for Research and Advanced Studies (ICREA), Barcelona, Spain. ⁵This comment refers to the article available online at https://doi.org/10.1038/s41598-021-04311-7. ✉email: dan.dediu@icrea.cat</footnote>
(focusing on their phonetics/phonology chapters), and phonological descriptions of speech sound inventories through minimal pairs. Second, we revised WSPD's coding using all the information they provide plus our new information, each decision being done by R.A.. This systematic procedure resulted in coding changes for 139 out of the 375 languages in the WSPD dataset, leading to a final dataset of 291 languages in 71 families (84 languages being excluded): 145 recoded as "trilled /r/" (vs 211 in WSPD) and 146 as "other" (vs 164); see Fig. 1.

Further, we not only replicated WSPD's Bayesian regressions using their R code, but we also extended them so that we better understand the role played by the various predictors, to better control for the effects of genealogy and geography, as well as to check the robustness of the results (see Supplementary materials). These extensions are: (i) we performed prior and posterior predictive checks, formal Bayesian hypothesis testing, and formal model comparisons, (ii) we conducted basic prior sensitivity analyses and we used alternative priors, (iii) we also fitted the same models using maximum likelihood, (iv) we included group level (or random) effects for language and area, (v) we included the Indo-European languages as well, (vi) we estimated the length of the actual forms used and we included this as a mediator, (vi) we used two global language phylogenies with branch lengths⁷,⁸ to better control for genealogy⁹, and (vii) we used a 2D Gaussian Process to better control for contact¹⁰. Moreover, we fixed some issues with the geographic locations of the languages and the Unicode coding of some word forms.

As a reminder, WSPD's main result is that the probability that a form contains “r” is much higher if it means “rough” (37% with a 95% credible interval of [14%, 61%]) than if it means “smooth” (10% [3%, 19%]) in languages coded as “trilled /r/”, but virtually the same in “other” languages (27% [12%, 45%] for “rough” vs 24% [11%, 41%] for “smooth”). Our results, using exactly the same computer code but the recoded data, do confirm the pattern for the “trilled /r/” languages (40% [16%, 63%] for “rough” vs 14% [5%, 25%] for “smooth”) but, interestingly, not for “other”, with a difference between “smooth” and “rough” comparable to that for “trilled /r/” languages (37% [13%, 65%]) for “rough” vs 18% [6%, 35%] for “smooth”), as shown in Fig. 2. Basically, while the difference between “rough” and “smooth” for “trilled /r/” is virtually identical between WSPD and our study, the recoding nullifies the difference between the “other” and “trilled /r/” categories. This pattern is supported by the analyses and extensions we performed, including by the omnibus model (where only meaning “rough” has a positive effect but not “trilled /r/”, nor their interaction), by the inclusion of a group level effect for language

<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Alluvial plot showing the effects of our re-coding. The strata (the vertical stacked bars) are: left: the original WSPD coding of 211 “trilled /r/” (yellow) vs 164 “other” (blue); middle: our recoding as 145 “trilled /r/” vs 146 “other”, plus “contrast” (gray) for 49 languages contrasting a trill, “undecidable” (dark gray) for 33 languages with insufficient information for a conclusion, and “error” (red) for 2 languages with wrong codes; right: the 291 languages included in our analysis (green; i.e., those re-coded as “trilled /r/” or “other”) vs the 84 excluded (white). The flows show the number of languages affected by recoding (e.g., 124 languages retaining the original “trilled /r/” code, 34 becoming “other”, 24 “contrast”, 38 “undecidable” and 1 “error”...).</figcaption></figure>
The original study

<figure><img src="image_4.png" /></figure>

Using the recoding

<figure><img src="image_5.png" /></figure>

p(/r/ | "rough") - p(/r/ | "smooth")

<figure><img src="image_6.png" /></figure>

**Fig. 2.** Comparing WSPD and the recoded results. Top and middle plots show the probability that a form uses /r/ if it means “rough” vs “smooth” in languages with a “trilled /r/” (left) vs “other” (right), in WSPD (top) and with the re-coded data (middle); colored circles represent families with size proportional to the number of languages; the big gray circles are the model predictions with 95% HDIs. The bottom plot shows the distribution of the difference in the same probabilities in languages with a “trilled /r/” (left, fully overlapping distributions) vs “other” (right) between WSPD (blue) and re-coded (yellow).

and of the Indo-European languages, by the use of global language phylogenies and a 2D Gaussian Process, and
by a mediation analysis showing that, even if words for “rough” tend to be longer, word length does not mediate
the effect of meaning “rough” on the probability of “r” (see Supplementary materials for the detailed results).

Our recoding, coupled with more extensive statistical analyses, show that the cross-modal tactile-sound
association identified by WSPD is more general than postulated since it is not restricted to the alveolar trill [r],
but concerns the whole class of “r”-like sounds (rhotics). WSPD implemented a careful and sound methodology,
but our results highlight even more the sensitivity to the primary data coding in general and especially for rhotics,
where our understanding of what they are and of their cross-linguistic patterning is limited. Interestingly, our
results also indicate that “auditory roughness” (characterized by WSPD as an intermittent airflow and vibration
specific to trills) cannot be the main cause to this tactile-sound association. Mechanistically explaining this
intriguing association may require detailed historical investigations and experimental cross-linguistic work such
as currently conducted for other instances of sound symbolism¹¹,¹² and for the “trilled /r/” itself¹³.

Data availability

All the data and R code, as well as an extensive supplementary materials HTML document supporting this paper
are freely available in the GitHub repository https://github.com/ddediu/r-roughness-recoding.

Received: 21 February 2024; Accepted: 14 March 2025

Published online: 15 April 2025

References

1. Winter, B., Sóskuthy, M., Perlman, M. & Dingemanse, M. Trilled /r/ is associated with roughness, linking sound and touch across spoken languages. *Sci. Rep.* **12**, 1035. https://doi.org/10.1038/s41598-021-04311-7 (2022).

2. Anselme, R. *La représentation du trill en typologie: de l'acoustique à l'inventaire phonémique* (Université Lumière Lyon 2, 2022). https://theses.hal.science/tel-04090606v1.

3. Anselme, R., Pellegrino, F. & Dediu, D. What's in the r? A review of the usage of the r symbol in the Illustrations of the IPA. *J. Int. Phon. Assoc.* https://doi.org/10.1017/S0025100322000238 (2023).

4. PHOIBLE Online. (Max Planck Institute for Evolutionary Anthropology, 2014). https://phoible.org/.

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Author contributions

R.A. coded the data and performed the first analysis. F.P. estimated the clean form length. D.D. checked and
extended the analysis and drafted the manuscript. All authors provided critical review and made substantial
revisions to the manuscript.

Declarations

Competing interests

The authors declare no competing interests.

Additional information

**Supplementary Information** The online version contains supplementary material available at https://doi.org/10.1038/s41598-025-94850-0.

**Correspondence** and requests for materials should be addressed to D.D.

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