Language trees ≠ gene trees

Darwin saw similarities between the evolution of species and the evolution of languages, and it is now widely accepted that similarities between related languages can often be interpreted in terms of a bifurcating descent history (‘phylogenesis’). Such interpretations are supported when the distributions of shared and unshared traits (for example, in terms of etymological roots for elements of basic vocabulary) are analysed using tree-building techniques and found to be well-explained by a phylogenetic model. In this article, we question the demographic assumption which is sometimes made when a tree-building approach has been taken to a set of cultures or languages, namely that the resulting tree is also representative of a bifurcating population history. Using historical census data relating to Gaelic- and English-speaking inhabitants of Sutherland (Highland Scotland), we have explored the dynamics of language death due to language shift, representing the extreme case of lack of congruence between the genetic and the culture–historical processes. Such cases highlight the important role of selective cultural migration (or shifting between branches) in determining the extinction rates of different languages on such trees.     

Language Evolution: Loquacious Monkey Brains?

Theories about the evolutionary path that led to the neuronal network underlying human language have long generated much heat without light. Using PET imaging, a recent study suggests that monkeys share a circuit for vocal perception with humans, adding some empirical data to the debate.     

Language Acquisition: When Does the Learning Begin?

Language acquisition is quite sophisticated by four months of age. Two cues that babies use to discriminate their language from another are the stress patterns of words and visual cues inherent in language production.     

The Elusive Honey Bee Dance “Language” Hypothesis

In the mid-1930s, Karl von Frisch proposed the equivalent of an odor-search hypothesis for honey bee recruitment to food sources. A decade later he switched to the equivalent of a dance language hypothesis (though he apparently did not consider his conclusions as hypotheses in either case). The later and more exotic hypothesis rapidly gained acceptance, but it failed its first experimental tests in the mid-1960s; searching recruits did not behave as von Frisch indicated they should under the language hypothesis. His earlier and more conservative odor-search hypothesis meshed better with results obtained in those test experiments. Language advocates then ignored basic precepts of scientific process, rejected and/or ignored results not in accord with their favored hypothesis, and instead repeatedly sought additional supportive evidence. While so doing, they inadvertently accumulated yet more evidence counter to von Frisch's original intent. By invoking ad hoc modifications and qualifications, advocates weakened, rather than strengthened, the hypothesis they continued to embrace. That strict adherence to the language hypothesis has had an unfortunate result; the exclusive investment in that line of research by various governmental agencies has failed to provide practical help to beekeepers or growers in the past half-century.     

Linguistic Relativity: Does Language Help or Hinder Perception?

A recent study has explored the interplay between language and perception through the brain's visual pathways. The results suggest an influence of linguistic categories on the speed of colour discrimination.     

Language and thought: does grammar makes us smart?

Many philosophers and psychologists believe that only people with rich language skills are capable of abstract reasoning. A man with a severe linguistic impairment poses a striking challenge to this view.     

Language Evolution: What Do Chimpanzees Have to Say?

Although unique in important ways, language shares some properties with other animal communication systems. Comparative analyses of nonhuman primate vocalizations can shed light on the evolution of language's special features.     

“Selling” Value: The Influence of Language on Willingness-to-Accept

In behavioral economics, the “endowment effect” describes the robust finding that prices people are willing to accept (WTA) for a good exceed prices people are willing to pay (WTP) for the same good. The increase in WTA values is often explained by the sellers’ negative hedonic response to losing their item. Recent studies, however, show that subtle cues may change participants’ perspective, influencing their valuations. We hypothesized that implicit connotations of instructional language may be one of those cues. To test this hypothesis we manipulated the wording of instructions in two conditions: in the Sell condition, subjects were endowed with a set of pens and asked to select an amount of money for which they would sell the pens back and in the Take condition, subjects were endowed with the pens and asked to select an amount of money they would take for the pens. Participants in each condition also estimated the market value of the pens. Consistent with our hypothesis, WTA in the Sell condition was higher than in the Take condition, though there were no differences in market values between conditions. These findings show that instructional language does influence participant valuations. Furthermore, we suggest that those being asked to “sell” use their market estimations as the salient reference point in the transaction.     

Infant Rule Learning: Advantage Language,or Advantage Speech?

Infants appear to learn abstract rule-like regularities (e.g., la la da follows an AAB pattern) more easily from speech than from a variety of other auditory and visual stimuli (Marcus et al., 2007). We test if that facilitation reflects a specialization to learn from speech alone, or from modality-independent communicative stimuli more generally, by measuring 7.5-month-old infants' ability to learn abstract rules from sign language-like gestures. Whereas infants appear to easily learn many different rules from speech, we found that with sign-like stimuli, and under circumstances comparable to those of Marcus et al. (1999), hearing infants were able to learn an ABB rule, but not an AAB rule. This is consistent with results of studies that demonstrate lower levels of infant rule learning from a variety of other non-speech stimuli, and we discuss implications for accounts of speech-facilitation.     

Grammatical Difficulties in Children with Specific Language Impairment: Is Learning Deficient?

Theoretical accounts of grammatical limitations in specific language impairment (SLI) have been polarized between those that postulate problems with domain-specific grammatical knowledge, and those that regard grammatical deficits as downstream consequences of perceptual or memory limitations. Here we consider an alternative view that grammatical deficits arise when the learning system is biased towards memorization of exemplars, and is poor at extracting statistical dependencies from the input. We examine evidence that SLI involves deficits in extracting nonadjacent dependencies from input, leading to reliance on rote learning, and consider how far this may be part of a limitation of procedural learning, or a secondary consequence of memory limitations.     

Mixing Languages during Learning? Testing the One Subject—One Language Rule

In bilingual communities, mixing languages is avoided in formal schooling: even if two languages are used on a daily basis for teaching, only one language is used to teach each given academic subject. This tenet known as the one subject-one language rule avoids mixing languages in formal schooling because it may hinder learning. The aim of this study was to test the scientific ground of this assumption by investigating the consequences of acquiring new concepts using a method in which two languages are mixed as compared to a purely monolingual method. Native balanced bilingual speakers of Basque and Spanish—adults (Experiment 1) and children (Experiment 2)—learnt new concepts by associating two different features to novel objects. Half of the participants completed the learning process in a multilingual context (one feature was described in Basque and the other one in Spanish); while the other half completed the learning phase in a purely monolingual context (both features were described in Spanish). Different measures of learning were taken, as well as direct and indirect indicators of concept consolidation. We found no evidence in favor of the non-mixing method when comparing the results of two groups in either experiment, and thus failed to give scientific support for the educational premise of the one subject—one language rule.     

How Accurate and Robust Are the Phylogenetic Estimates of Austronesian Language Relationships?

We recently used computational phylogenetic methods on lexical data to test between two scenarios for the peopling of the Pacific. Our analyses of lexical data supported a pulse-pause scenario of Pacific settlement in which the Austronesian speakers originated in Taiwan around 5,200 years ago and rapidly spread through the Pacific in a series of expansion pulses and settlement pauses. We claimed that there was high congruence between traditional language subgroups and those observed in the language phylogenies, and that the estimated age of the Austronesian expansion at 5,200 years ago was consistent with the archaeological evidence. However, the congruence between the language phylogenies and the evidence from historical linguistics was not quantitatively assessed using tree comparison metrics. The robustness of the divergence time estimates to different calibration points was also not investigated exhaustively. Here we address these limitations by using a systematic tree comparison metric to calculate the similarity between the Bayesian phylogenetic trees and the subgroups proposed by historical linguistics, and by re-estimating the age of the Austronesian expansion using only the most robust calibrations. The results show that the Austronesian language phylogenies are highly congruent with the traditional subgroupings, and the date estimates are robust even when calculated using a restricted set of historical calibrations.