Language Evolution and Computation Bibliography

We make the case that, contra standard assumption in linguistic theory, the sound systems of human languages are adapted to their environment. While not conclusive, this plausible case rests on several points discussed in this work: First, human behavior is generally adaptive and the assumption that this characteristic does not extend to linguistic structure is empirically unsubstantiated. Second, animal communication systems are well known to be adaptive within species across a variety of phyla and taxa. Third, research in laryngology demonstrates clearly that ambient desiccation impacts the performance of the human vocal cords. The latter point motivates a clear, testable hypothesis with respect to the synchronic global distribution of language types. Fourth, this hypothesis is supported in our own previous work, and here we discuss new approaches being developed to further explore the hypothesis. We conclude by suggesting that the time has come to more substantively examine the possibility that linguistic sound systems are adapted to their physical ecology.

The recent growth of Experimental Semiotics (ES) offers us a new option to investigate human communication. We briefly introduce ES, presenting results from three themes of research which emerged within it. Then we illustrate the contribution ES can make to the investigation of human communication systems, particularly in comparison with the other existing options. This comparison highlights how ES can provide an engine of discovery for understanding human communication. In fact, in complementing the other options, ES offers us unique opportunities to test assumptions about communicative behavior, both through the experimenters' planned manipulations and through the unexpected behaviors humans exhibit in experimental settings. We provide three examples of such opportunities, one from each of the three research themes we present.

Formal models of cultural evolution have illustrated circumstances under which behavioral traits that have no inherent advantage over others can undergo positive selection pressure. One situation in which this may occur is when the behavior functions as a social marker, and there is pressure to identify oneself as a member of a particular group. Our aim in the current study was to determine whether participants organized into subpopulations could effectively exploit variation in a completely novel behavior to advertise themselves as belonging to a particular subpopulation, such that discrimination between in-group and out-group members was possible and subpopulations exhibited increasing distinctiveness. Eighty participants took part, organized into four subpopulations, each composed of five four-member generations. They each completed a tower-building task, used in previous experimental studies of cultural evolution. An incentive payment structure was imposed with the aim of motivating participants to advertise themselves as belonging to a particular subpopulation and to distinguish in-group members from members of other subpopulations. The first generation were exposed to photographs of randomly assigned “seed” towers, and later generations were exposed to photographs of the towers built by the members of the previous generation of their own subpopulation. Participants were able to discriminate towers built by in-group members of the same generation, from towers built by out-group members. Over generations, tower designs evolved such that they were increasingly identifiable as belonging to a particular subpopulation. Arbitrary traits which had no prior advantage became associated with group membership, providing empirical support for theoretical models.

The concept of duality of patterning (henceforth DP) has recently begun to undergo new scrutiny. In particular, the fact that Al-Sayyid Bedouin Sign Language (ABSL) does not appear to exhibit a layer of meaningless units (Sandler et al. 2011) casts doubt on the universality of DP as a defining feature of natural language. Why, then, do the vast majority of the world's languages exhibit DP? Two hypotheses have been suggested. The first is that DP is a necessary solution to the problem of conveying a large number of meanings; the second is that DP arises as a consequence of conventionalization. We tested these hypotheses in an experimental-semiotics study. Our results supported the hypothesis based on conventionalization but were inconclusive with regard to the hypothesis based on the number of meanings. At the same time, the task of measuring DP in an experimental-semiotics study presented interesting challenges, suggesting that the concept of DP may need some overhauling.

Computational simulations have provided evidence that the use of linguistic cues as group markers plays an important role in the development of linguistic diversity shortcite (Nettle & Dunbar, 1997; Nettle, 1999). Other simulations, however, have contradicted these findings (Livingstone & Fyfe, 1999; Livingstone, 2002). Similar disagreements exist in sociolinguistics (e.g. Labov, 1963, 2001; Trudgill, 2004, 2008a; Baxter et al., 2009). This paper describes an experimental study in which participants played an anonymous economic game using an instant-messenger-style program and an artificial aalien languagea. The competitiveness of the game and the frequency with which players interacted were manipulated. Given frequent enough interaction with team-mates, players were able to use linguistic cues to identify themselves. In the most competitive condition, this led to divergence in the language, which did not occur in other conditions. This suggests that both frequency of interaction and a pressure to use language to mark identity play a significant role in encouraging linguistic divergence over short periods, but that neither is suffi cient on its own.

Change and variation, while inherent to language, might be seen as running counter to human communicative needs. However, variation also gives language the power to convey reliable indexical information about the speaker. This has been argued to play a significant role in allowing the establishment of large communities based on cooperative exchange (M. Enquist and O. Leimar 1993, The evolution of cooperation in mobile organisms. Animal Behaviour 45: 747a757; R. I. M. Dunbar 1996, Grooming, Gossip and the Evolution of Language. London: Faber and Faber), although there has been little experimental investigation of the hypothesis. Here I present a preliminary study intended to help fill this gap. Participants played an online team game in which they negotiated anonymously for resources using an artificial language. Players succeeded in using linguistic cues to distinguish between their teammates and their opponents, and displayed between-team variation in the use of the language.