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 ‘alien language’. 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.

Significance: Do we talk about some colors more often than others? And do the colors we communicate about most frequently vary across cultures? A classic finding shows that languages around the world partition colors into words in remarkably similar, although not identical, ways. The biology of human color perception helps explain similar color vocabularies across languages, but less is known about how often speakers need to reference different colors. The inference method we develop reveals extensive variation in communicative needs across colors, and a diversity in needs across 130 languages, which helps explain variation in their color vocabularies. Our results open the door to studying cross-cultural variation in demands on different colors, and factors that drive color demands in linguistic communities.

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.