T. Mark Ellison

Creating a communication system from scratch: gesture beats vocalization hands down.

How does modality affect peoples ability to create a communication system from scratch? The present study experimentally tests this question by having pairs of participants communicate a range of pre-specified items (emotions, actions, objects) over a series of trials to a partner using either non-linguistic vocalization, gesture or a combination of the two. Gesture-alone outperformed vocalization-alone, both in terms of successful communication and in terms of the creation of an inventory of sign-meaning mappings shared within a dyad (i.e., sign alignment). Combining vocalization with gesture did not improve performance beyond gesture-alone. In fact, for action items, gesture-alone was a more successful means of communication than the combined modalities. When people do not share a system for communication they can quickly create one, and gesture is the best means of doing so.

The Cultural Evolution of Human Communication Systems in Different Sized Populations: Usability Trumps Learnability

This study examines the intergenerational transfer of human communication systems. It tests if human communication systems evolve to be easy to learn or easy to use (or both), and how population size affects learnability and usability. Using an experimental-semiotic task, we find that human communication systems evolve to be easier to use (production efficiency and reproduction fidelity), but harder to learn (identification accuracy) for a second generation of naïve participants. Thus, usability trumps learnability. In addition, the communication systems that evolve in larger populations exhibit distinct advantages over those that evolve in smaller populations: the learnability loss (from the Initial signs) is more muted and the usability benefits are more pronounced. The usability benefits for human communication systems that evolve in a small and large population is explained through guided variation reducing sign complexity. The enhanced performance of the communication systems that evolve in larger populations is explained by the operation of a content bias acting on the larger pool of competing signs. The content bias selects for information-efficient iconic signs that aid learnability and enhance usability.

Cultural selection drives the evolution of human communication systems

Human communication systems evolve culturally, but the evolutionary mechanisms that drive this evolution are not well understood. Against a baseline that communication variants spread in a population following neutral evolutionary dynamics (also known as drift models), we tested the role of two cultural selection models: coordination- and content-biased. We constructed a parametrized mixed probabilistic model of the spread of communicative variants in four 8-person laboratory micro-societies engaged in a simple communication game. We found that selectionist models, working in combination, explain the majority of the empirical data. The best-fitting parameter setting includes an egocentric bias and a content bias, suggesting that participants retained their own previously used communicative variants unless they encountered a superior (content-biased) variant, in which case it was adopted. This novel pattern of results suggests that (i) a theory of the cultural evolution of human communication systems must integrate selectionist models and (ii) human communication systems are functionally adaptive complex systems.

FREQUENCY-DEPENDENT BIAS AFFECTS THE SPREAD OF HUMAN COMMUNICATION SYSTEMS

Majority influence is well established in social psychology. Boyd and Richerson (1985) proposed a frequency-dependent bias in cultural transmission, such that the frequency of a behaviour is used as an indirect measure of its merit and affects its likelihood of adoption. Such a bias may affect the evolution of language, and may have done so for millennia, by influencing how linguistic variants spread through populations. The present study tested whether the frequency of signs in an experimentalsemiotic communication task (similar to Fay et al., 2010; Garrod et al., 2007) influenced the degree to which they were copied. It was hypothesized that majority signs would be copied more than minority signs.

BIASED COPYING IN THE EVOLUTION OF HUMAN COMMUNICATION SYSTEMS

People copy one another’s utterances during communication (Garrod & Anderson, 1987). In laboratory micro-societies this copying leads to the creation of shared communication systems (Fay, Garrod, Roberts, & Swoboda, 2010). If biased copying is seen in human communication, such that some individuals are more likely to be copied than others, certain individuals will have a disproportionate influence on the evolution of their communication system. People copy others they perceive to be skilful, successful, prestigious or similar to themselves (Henrich & McElreath, 2003; Richerson & Boyd, 2005). The present study tested whether people exhibit biased copying in a communication task similar to the game PictionaryTM. It is hypothesized that participants will copy the drawings of others more when told the drawer was skilful, successful, prestigious or similar to themselves (than when told the opposite).