Language Log

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.