Deviations from optimality should be an integral part of a working definition of SMC

People infer communicative action through an expectation for efficient communication

Humans often communicate using body movements like winks, waves, and nods. However, it is unclear how we identify when someone’s physical actions are communicative. Given people’s propensity to interpret each other’s behavior as aimed to produce changes in the world, we hypothesize that people expect communicative actions to efficiently reveal that they lack an external goal. Using computational models of goal inference, we predict that movements that are unlikely to be produced when acting towards the world and, in particular, repetitive ought to be seen as communicative. We find support for our account across a variety of paradigms, including graded acceptability tasks, forced-choice tasks, indirect prompts, and open-ended explanation tasks, in both market-integrated and non-market-integrated communities. Our work shows that the recognition of communicative action is grounded in an inferential process that stems from fundamental computations shared across different forms of action interpretation.

Humans can quickly infer when someone’s body movements are meant to be communicative. Here, the authors show that this capacity is underpinned by an expectation that communicative actions will efficiently reveal that they lack an external goal.

Evaluating the relative contributions of copying and reconstruction processes in cultural transmission episodes

The ability to transmit information between individuals through social learning is a foundational component of cultural evolution. However, how this transmission occurs is still debated. On the one hand, the copying account draws parallels with biological mechanisms for genetic inheritance, arguing that learners copy what they observe and novel variations occur through random copying errors. On the other hand, the reconstruction account claims that, rather than directly copying behaviour, learners reconstruct the information that they believe to be most relevant on the basis of pragmatic inference, environmental and contextual cues. Distinguishing these two accounts empirically is difficult based on data from typical transmission chain studies because the predictions they generate frequently overlap. In this study we present a methodological approach that generates different predictions of these accounts by manipulating the task context between model and learner in a transmission episode. We then report an empirical proof-of-concept that applies this approach. The results show that, when a model introduces context-dependent embedded signals to their actions that are not intended to be transmitted, it is possible to empirically distinguish between competing predictions made by these two accounts. Our approach can therefore serve to understand the underlying cognitive mechanisms at play in cultural transmission and can make important contributions to the debate between preservative and reconstructive schools of thought.

Efficiency is prioritised over fairness when distributing joint actions

Individuals have a drive towards maximising action efficiency, which is reflected in action choices that minimise movement costs to reach a goal. In joint actions, actors prioritise joint efficiency or coefficiency, maximising the utility of the joint action even if this comes at a cost to themselves. However, it remains an open question whether actors are willing to unilaterally sacrifice their partner's individual efficiency for the greater good, when forcing a partner to incur additional costs may be interpreted as unfair. In two experiments we explored how participants would choose to distribute a motor task that required either a fair or an unfair distribution of labour. We found that, both whether there was opportunity for reciprocity (Experiment 1) or not (Experiment 2), participants maximised the coefficiency of their joint actions, regardless of how unfair this distribution of labour proved to be regarding the individual action costs. Taken together, our results suggest participants use a rational decision-making framework that prioritises overall efficiency over both individual efficiency and a consideration of fairness.