We investigated the emergence of register-like indexical associations, whereby linguistic forms that are associated with groups of speakers acquire novel associations with contextual features of those groups. We employed an artificial-language paradigm in which participants were exposed to an “alien” language spoken by two alien species wearing two different ceremonial outfits. The language varied with respect to plural suffixes, such that one suffix was associated reliably with one species and outfit in training. We then tested participants on what associations they had acquired. In two experiments we manipulated which aliens wore which outfits in the test phase. Regardless of condition or length of training, participants associated suffixes strongly with aliens rather than clothing. In a third experiment we introduced a new alien species in the test phase. For these aliens, which participants had not seen during training, participants made a clear association based on outfit. These results show clearly ranked indexical (or proto-indexical) associations on the part of participants and lay clear groundwork for the experimental investigation of the emergence of indexical social meaning in language.

Vowel systems exhibit organization, and several theoretical ac-counts have been proposed to explain this. A prominent ac-count explains organization in terms of maximizing the disper-sion of vowels, increasing acoustic perceptibility while reduc-ing articulatory effort. This implies modality-independence,but leaves open questions about the extent to which dispersionis driven by articulatory or acoustic pressures. We investigatedwhether vowel-like organization would emerge in a novel vi-sual communication system in the laboratory, in which partic-ipants took turns to send color signals to communicate a set ofanimal referents by moving their fingers around a color space.We manipulated the extent to which sender and receiver needswere aligned. Overall, systems exhibited significant levels ofdispersion; participants also took into account receiver needs,withconsequences for the structure of the resulting systems.

Languages are subject to many competing pressures, whichoriginate in individual-level learning and communication bi-ases and in social biases reflecting community-level dynamics.Recent work suggests that certain aspects of language struc-ture, such as the cross-linguistic trade-off between case andconstituent-order flexibility, originate in learners’ biases forefficient communication: Learners drop redundant case but re-tain informative case in production. Social biases can lead toretention of redundant case, resulting in systems that requiremore effort to produce. It is not clear, however, whether socialbiases can influence the use of informative cues. We tested thisby exposing participants to a language with uninformative con-stituent order and two dialects, only one of which employedcase. We manipulated the presence of social biases for andagainst the case dialect. Learners biased towards the no-casedialect dropped informative case without compensating for theresulting message uncertainty. Case was retained in all otherconditions.

The spread of cultural variants, such as dress or speech pat-terns, may be promoted or inhibited by different types of bias.In model-based bias, variants are differentially adopted accord-ing to characteristics of individuals exhibiting them. A surpris-ing case of cross-group adoption comes from sociolinguisticfieldwork in which White speakers were observed exhibiting afeature of African-American Vernacular English, in spite of ex-pressing aggressively negative attitudes towards their African-American neighbors. A likely explanation for this is that thefeature in question had become dissociated for these speakersfrom the inalienable trait Blackness, but had retained associa-tions with the more alienable trait of being “street” or tough.We tested this by conducting an artificial-language experimentin which groups of four participants played a computer gamethat involved typing instant messages to each other, tradingresources, and fighting. Participants were assigned to one oftwo mutually antagonistic “alien species” (weaker Wiwos andtougher Burls) and learned an alien language with two species-specific dialects. In one condition, the Wiwos were told thatthat Burl dialect was mainly used by Burls; in the other con-dition they were told it was mainly used by “tougher aliens”.Burl variants were significantly more likely to be used by Wi-wos in the latter condition than in the former, even though theywere associated with tougher aliens in both conditions. Thissuggests that cultural variants linked to more alienable traitsare more likely to be adopted than those linked to inalienableones, even if the practical implications of the two traits are verysimilar.

Labels may play a role in the formation and acquisition of object categories. We investigated this using a free-categorization task, manipulating the presence or absence of labels and whether labels were random or reinforced one of two alternative categorization cues (taxonomic or thematic relationships). When labels were absent, participants used thematic and taxonomic cues equally to categorize stimuli. When present, labels were used as the primary cue for category formation, with random labels leading participants to attend less to taxonomic and thematic relations between stimuli. When labels redundantly reinforced either thematic or taxonomic cues, the use of the cue in question was boosted along with the use of labels as a cue for categorization. Most interestingly, in spite of previously observed associations between labels and taxonomic grouping, labels did not preferentially boost the use of either taxonomic or thematic cues in comparison with the other.

We present an experimental study investigating the role ofinformation-theoretic factors in determining patterns of redun-dancy and focus in language and other communication sys-tems. Pairs of participants played a simple communicationgame using a non-linguistic visual medium to send messagesto each other. We manipulated noise, effort, and time pres-sures and measured message length, redundancy, and accuracy.Participants behaved as predicted based on an information-theoretic model, with message length and redundancy varyingaccording to circumstance, but accuracy remaining constant.

We investigated the emergence of dispersion in phonological systems using an established experimental paradigm in which pairs of participants play a non-linguistic communication game, taking turns to select discrete colors from a continuous underlying space and send them to each other to communicate animal silhouettes. Over time participants established sets of signals made up of combinatorial color units, analogous to the phonemes of natural language. This allowed us to investigate the role of interactive pressures on the emergence of organizational structure in phonological inventories, principally dispersion. We manipulated minimum signal length (as a means of investigating the role of coarticulation) and the presence of probabilistic noise. We also manipulated the nature of the underlying color space. There was an effect of colorspace but not of noise or minimum signal-length. However, dispersion occurred at above-chance levels in all conditions. Our results provide evidence for the role of communicative interaction in the emergence and cultural evolution of phonological structure.

Corpus data suggests that frequent words have lower rates of replacement and regularization. It is not clear, however, whether this holds due to stronger selection against innovation among high-frequency words or due to weaker drift at high frequencies. Here, we report two experiments designed to probe this question. Participants were tasked with learning a simple miniature language consisting of two nouns and two plural markers. After exposing plural markers to drift and selection of varying strengths, we tracked noun regularization. Regularization was greater for low- than for high-frequency nouns, with no detectable effect of selection. Our results therefore suggest that lower rates of regularization of more frequent words may be due to drift alone.

Language is widely assumed to be a well designed tool for re-liably communicating propositional information between peo-ple. This suggests that its users should be sensitive to failuresof communication, such as utterances that are blatantly inco-herent with respect to an ongoing conversation. We presentexperimental work suggesting that, in fact, people are surpris-ingly tolerant of conversational incoherence. In two previousstudies, participants engaged in instant-messaging conversa-tions that were either repeatedly crossed with other conversa-tions or had lines inserted into them that deliberately contra-dicted available information. In both cases, a substantial pro-portion of participants failed to notice. In a new study, confed-erates inserted unexpected, nonsensical lines into face-to-faceconversations. The majority of participants failed to notice.We argue these findings suggest that we should be wary ofmodeling spontaneous communication in terms of faithful in-formation transmission, or language as a well designed tool forthat purpose.