Abstract: Languages describe “who is doing what to whom” by distinguishing the event roles of agent (doer) and patient (undergoer), but it is debated whether they result from nonlinguistic representations that may already exist in preverbal infants and nonhuman animals. The phenomenon of causal perception, where the subsequent movements of two objects A and B evoke the impression of A launching B, is a simple depiction of an agent-patient relation. The seminal study by Leslie and Keeble from 1987 proposed that infants of 6 months old may be able to attribute agent and patient roles to such causal displays, after they demonstrated the infants’ dishabituation upon seeing a launching event that was reversed. They introduced the idea that a role reversal had taken place upon reversing the direction of the launching event (launcher becoming launchee), but not in a noncausal temporal gap event where the agent and patient roles were not present. The present study tested this hypothesis in three different populations: 6-month-old human infants, human adults, and Guinea baboons (Papio papio). For the human infants, we applied a habituation-dishabituation design, and for the human adults and baboons, a conditional match-to-sample task. We were unable to replicate the findings of Leslie and Keeble in human infants. Similarly, we did not find evidence for an effect specific to reversing launching events in human adults and baboons. Inconsistent results across different studies call into question the role reversal paradigm for Michottean launches to study event role attribution.
Category: Language
What enables human language? A biocultural framework
Abstract: Explaining the origins of language is a key challenge in understanding ourselves as a species. We present an empirical framework that draws on synergies across fields to facilitate robust studies of language evolution. The approach is multifaceted, seeing language emergence as dependent on the
convergence of multiple capacities, each with their own evolutionary trajectories. It is explicitly biocultural, recognizing and incorporating the importance of both biological preparedness and cultural transmission as well as interactions between them. We demonstrate this approach through three
case studies that examine the evolution of different facets involved in human language (vocal production learning, linguistic structure, and social underpinnings).
Testing semantic compositionality in baboons (Papio papio) through relearning and generalization
Abstract: This study investigates whether baboons are capable of semantic compositionality, specifically, whether they can apply compositional rules to new situations (generalization). In language, semantic compositionality is linked to productivity, the generalization of a rule to new combinations. Across four experiments, baboons were trained to match visual stimuli based on either shape or color depending on symbolic cues. Experiments 1–3 tested generalization under different task complexities but consistently failed to show evidence that baboons understood or applied the matching rules beyond memorized combinations. Only in Experiment 4, which used a relearning paradigm rather than generalization, did baboons show improved performance when the rule remained consistent across phases. Four hypotheses were explored to explain the lack of generalization: an iconicity-novelty bias, the possibility that compositionality is present, but that training was not sufficient for generalization, rote memorization of cue-sample pairs, and a difference between implicit and explicit learning. The findings do not allow us to discriminate between these hypotheses.
A comparative study of causal perception in Guinea baboons (Papio papio) and human adults
Abstract: In humans, simple 2D visual displays of launching events (“Michottean launches”) can evoke the impression of causality. Direct launching events are regarded as causal, but similar events with a temporal and/or spatial gap between the movements of the two objects, as non-causal. This ability to distinguish between causal and non-causal events is perceptual in nature and develops early and preverbally in infancy. In the present study we investigated the evolutionary origins of this phenomenon and tested whether Guinea baboons (Papio papio) perceive causality in launching events. We used a novel paradigm which was designed to distinguish between the use of causality and the use of spatiotemporal properties. Our results indicate that Guinea baboons successfully discriminate between different Michottean events, but we did not find a learning advantage for a categorisation based on causality as was the case for human adults. Our results imply that, contrary to humans, baboons focused on the spatial and temporal gaps to achieve accurate categorisation, but not on causality per se. Understanding how animals perceive causality is important to figure out whether non-human animals comprehend events similarly to humans. Our study hints at a different manner of processing physical causality for Guinea baboons and human adults.