Language Log

Ian Maddieson and Christophe Coupé, "Human spoken language diversity and the acoustic adaptation hyothesis", ASA 2015

Bioacousticians have argued that ecological feedback mechanisms contribute to shaping the acoustic signals of a variety of species and anthropogenic changes in soundscapes have been shown to generate modifications to the spectral envelope of bird songs. Several studies posit that part of the variation in sound structure across spoken human languages could likewise reflect adaptation to the local ecological conditions of their use. Specifically, environments in which higher frequencies are less faithfully transmitted (such as denser vegetation or higher ambient temperatures) may favor greater use of sounds characterized by lower frequencies. Such languages are viewed as “more sonorous”. This paper presents a variety of tests of this hypothesis.  

Data on segment inventories and syllable structure is taken from LAPSyD, a database on phonological patterns of a large worldwide sample of languages. Correlations are examined with measures of temperature, precipitation, vegetation, and geomorphology reflecting the mean values for the area in which each language is traditionally spoken. Major world languages, typically spoken across a range of environments, are excluded. Several comparisons show a correlation between ecological factors and the ratio of sonorant to obstruent segments in the languages examined offering support for the idea that acoustic adaptation applies to human languages.

A recent conversation with Didier Demolin about animal vocalizations motivated me to return to a an issue discussed in "Finch linguistics", 7/15/2011. (See also "Markov's heart of darkness", 7/18/2011, "Non-Markovian yawp", 9/18/2011, and "The long get longer", 12/4/2013.)

The point is this: In modeling the structure of simple repetitive behavior, considerations from (traditional) formal language theory can obscure rather than clarify the issues. These threats to insight include the levels of the Chomsky-Schützenberger hierarchy, the "recursion" controversy, and so on.

What follows is an attempt at a simple illustrated explanation.

As you know, I serve Language Log as occasional film reviewer. I reported on Rise of the Planet of the Apes when it came out (see "Caesar and the power of No", August 14, 2011). So I naturally went to see the sequel, Dawn of the Planet of the Apes, to report on the way the franchise was developing its view of how apes evolve language. Well, forgive me if this seems pedantic, but the film is supposed to be science fiction, and I have to say that the linguistic science is crap.

I left the cinema half stunned by the visual effects (which are absolutely terrific — worth the price of admission) and half deafened by the soundtrack and Michael Giacchino's bombastic score, but thoroughly disappointed at the inconsistent muddle of the way apes' linguistic powers were portrayed.

I recently read through Marc Hauser et al., "The Mystery of Language Evolution", Frontiers in Psychology 2014, which expresses a strongly skeptical view on every aspect of the topic, including this one:

[S]tudies of nonhuman animals provide virtually no relevant parallels to human linguistic communication, and none to the underlying biological capacity.

You'll search Google News in vain for stories about most technical terms in phonetics — no recent coverage of lenition, for example — but "vocal fry" has been prominent in the popular press for several years. Despite all the coverage, many people seem to be unclear about what it is and where it comes from — so today I thought I'd spend a few minutes on the phenomenon from a phonetician's perspective.

The paper that Geoff referred to a bit earlier today is Madhura Ingalhalikar et al., "Sex differences in the structural connectome of the human brain", PNAS 2013. It features a very impressive graphic showing sex differences in connectivity of regions within the brain, indicating a pattern where males (top row in the figure) "had greater within-hemispheric connectivity, as well as enhanced modularity and transitivity", whereas "between-hemispheric connectivity and cross-module participation predominated in females" (bottom row in the figure). This is argued to suggest that "male brains are structured to facilitate connectivity between perception and coordinated action, whereas female brains are designed to facilitate communication between analytical and intuitive processing modes".

Geoff linked to a letter from Rae Langton and John Dupré, which argues that "if the mind is the brain, any mental difference will be a brain difference", and that "training up half of humanity one way, half another" will inevitably create mental differences, which will correspond to brain differences, so that it's a mistake to see these results as necessarily a "deterministic fairy tale" about evolutionary biology, rather than a consequence of contemporary cultural differences.

This is all true, but I wonder whether something even simpler might be going on.

[Warning: More than usually geeky…]

During the past decade or two, there's been a growing body of work arguing for a special connection between endogenous brain rhythms and timing patterns in speech. Thus Anne-Lise Giraud & David Poeppel, "Cortical oscillations and speech processing: emerging computational principles and operations", Nature Neuroscience 2012:

Neuronal oscillations are ubiquitous in the brain and may contribute to cognition in several ways: for example, by segregating information and organizing spike timing. Recent data show that delta, theta and gamma oscillations are specifically engaged by the multi-timescale, quasi-rhythmic properties of speech and can track its dynamics. We argue that they are foundational in speech and language processing, 'packaging' incoming information into units of the appropriate temporal granularity. Such stimulus-brain alignment arguably results from auditory and motor tuning throughout the evolution of speech and language and constitutes a natural model system allowing auditory research to make a unique contribution to the issue of how neural oscillatory activity affects human cognition.

This is a guest post by Margaret Wilson.

Turn-taking is fundamental to human conversation, so the question of whether it occurs in other social animals is extremely interesting. A new paper on turn-taking in marmoset monkeys (Takahashi et al., "Coupled Oscillator Dynamics of Vocal Turn-Taking in Monkeys", Current Biology, 2013) is to be applauded for tackling this issue.

Unfortunately, though, it is not clear that their data demonstrate turn-taking in any sophisticated sense: specifically (and this is the sense embraced by the authors), entrainment of timing mechanisms between two individuals to regulate the passing of the turn. They begin by asking, "Is this a simple call-and-response (‘‘antiphonal’’) behavior seen in numerous species, or is it a sustained temporal coordination of vocal exchanges as in human conversation?" They conclude that they have shown the latter, but, on my reading, all their data is compatible with simple call-and-response. What seems to be going on is that the authors have failed to appreciate just how weird human turn-taking is.

Last week, when I discussed the return of the zombie meme about women talking three times more than men ("An invented statistic returns", 2/22/2013),  I promised to come back to the real scientific results in the paper whose public relations campaign unleased that extraordinary outburst of mass-media pseudoscience.

The paper was J. Michael Bowers, Miguel Perez-Pouchoulen, N. Shalon Edwards, and Margaret M. McCarthy, "Foxp2 Mediates Sex Differences in Ultrasonic Vocalization by Rat Pups and Directs Order of Maternal Retrieval", The Journal of Neuroscience, February 20, 2013, As the title indicates, the paper is mostly about baby rats; and the reader is hereby warned that the following discussion may be longer than you're going to be willing to sit through. I'm afraid, though, that if you care about what this paper said and what it means, you're going to have to put in some time, here or elsewhere.