Biology subjects

Townsend, S. W.

Publications and source records attributed to Townsend, S. W..

8 recordsLinked to original sources

bioRxiv2026

Non-trivial compositionality in chimpanzees: an experimental demonstration

Compositional syntax - the ability to combine meaningful units into structured sequences whose overall meaning depends on both the meanings of the parts and their combination - is a hallmark of human language. Recent work suggests that chimpanzees may exhibit similar capacities, raising the possibility that compositionality predates the emergence of language in humans. However, a key challenge has been to exclude simpler explanations in which call combinations are processed as independent utterances rather than integrated structures. Here, we address this issue using a source-manipulation paradigm in playback experiments with captive chimpanzees (n = 6) at the Sigean African Reserve, France. We presented sequences combining alarm and recruitment calls either from a single source (one loudspeaker) or from two spatially distinct sources (two loudspeakers). If sequences are interpreted as independent calls, responses should not differ between conditions. Instead, chimpanzees responded significantly faster when sequences originated from a single source. Bayesian survival analyses confirmed this effect. These results support a non-trivial form of compositionality, whereby the meaning of call combinations depends on their integration into a unified sequence produced by a single individual. Our findings provide experimental evidence that key features of linguistic compositionality may have evolutionary roots in the primate lineage.

animal behavior and cognition↗

bioRxiv2026

Supra-regular recursion in primate vocal sequences

Complex syntax is the widely accepted demarcation between animal and human communication. Although animal vocal systems occasionally contain pockets of syntax-like structures, their grammars are thought to be at best regular, whereas human language is supra-regular, i.e., including at least context-free computational complexity. Leveraging a new likelihood method for probabilistic formal grammars, we show that the call sequences of three phylogenetically diverse nonhuman primates (bonobos, olive colobus monkeys, common marmosets) include parts that are most likely generated by supra-regular recursive grammars, similar to human language. These findings challenge syntax as the major transition in hominid evolution and opens up prospects for alternative evolutionary scenarios.

animal behavior and cognition↗

bioRxiv2026

Animal collocation revisited: intercohort comparison and a case study comparing call combinations between sexes in common marmosets

Many animals communicate using sequences of signals, but identifying recurrent, non-random signal combinations remains methodologically challenging. Collocation analyses are increasingly popular approaches for detecting which signals animals combine at rates greater than expected by chance. However, existing methods for animal collocation analysis face several limitations that reduce their statistical rigour: they lack uncertainty estimates, fail to control for non-independence in sampled data, and do not account for inflated family-wise error rates when identifying attraction among many different signal types. These limitations restrict the broader applicability of animal collocation analysis, including preventing robust comparisons of signal combination strength between cohorts (e.g. populations, sexes or age classes). We adapt a novel form of Multiple Distinctive Collocation Analysis using Pearson residuals (MDCA-Pr) that addresses these statistical limitations, and validate its use in animal communication research in three ways: first, using numerous simulated datasets of different sizes and levels of signal recombination; second, using simulated data to evaluate the performance of MDCA-Pr in intercohort comparisons, and third, by demonstrating how MDCA-Pr can be applied to compare the vocal sequences produced by male and female captive-living common marmosets (Callithrix jacchus). MDCA-Pr shows high sensitivity, including at small sample sizes, and generally low false-positive rates, which we further reduce by applying additional criteria for identifying attraction between signals. During intercohort comparisons, MDCA-Pr is conservative, with low false-positive rates, and statistical power increases with sample size. MDCA-Pr is a robust method for evaluating signal attraction in animal communication and enables accurate intercohort comparison of animal signal combinations. Significance StatementBy assessing the performance of MDCA-Pr on simulated animal-like data, we demonstrate that this method reliably detects signal combinations within and across animal cohorts, while overcoming statistical limitations of previous collocation analyses. We present an analytical pipeline for applying MDCA-Pr to animal signal data, including for intercohort comparisons, enabling identification and comparison of combinatorial strategies across entire signal repertoires. We illustrate this approach by comparing call combination strategies of male and female common marmosets when presented with food under experimental conditions, finding similar combinatorial strategies between sexes. MDCA-Pr therefore permits rigorous characterization of animal signal combinatoriality and opens avenues for investigating how demographic, social, and group-level factors influence combinatorial patterns.

animal behavior and cognition↗

bioRxiv2025

Domestic goats can follow the direction of human voices to solve a hidden-object task

The capacity for animals to produce and comprehend vocalisations that provide referential acoustic cues to their eliciting cause (e.g. predator-specific alarm calls and food calls) is a highly adaptive means of maximising the benefits of group living, and has been widely studied in diverse species. However, an underexplored dimension of referentiality is the ability to process the direction in which a vocalisation is emitted as a cue towards its referent. Here, we replicated an experimental design previously applied to dogs, chimpanzees and human infants to investigate whether domestic goats (Capra hircus) can use human voices as a directional cue in a hidden-object task. Twenty-nine goats from a UK sanctuary participated in three experimental conditions. In each condition, goats were individually presented with a human experimenter obscured by a barrier, and two identical containers, one of which was baited with food. In the reward directed speech condition, the experimenter vocalised excitedly towards the baited container while sitting closer to the un-baited container, and then the goat was able to select which container to explore. While substantial inter-individual variation existed, on average, subjects chose the baited container at above chance level across the four trials. Two control conditions explored alternative explanations for this result: a "no speech" condition, in which the experimenter was silent but remained in the same location as in the test condition, and a "non-reward directed speech" condition, in which the experimenter directed their voice away from both containers. Subjects showed no evidence of choosing the baited container at above chance level in either of these control conditions. We conclude that goats, like dogs, but not chimpanzees, are capable of attending to the directional cues provided by human voices, and discuss the possible role of domestication in the taxonomic distribution of this ability.

animal behavior and cognition↗

bioRxiv2025

An updated vocal repertoire of wild adult bonobos (Pan paniscus )

While research over the last 20 years has shed important light on the vocal behaviour of our closest living relatives, bonobos and chimpanzees, a quantitative description of their full vocal repertoire is absent. Such data are critical for a holistic understanding of a species communication system and unpacking how these systems compare more broadly with other primate and non-primate species. Here we make key progress by providing the first quantitative Pan vocal repertoire, specifically for wild bonobos. Using data comprising over 1500 calls from 53 adult individuals collected over 33 months, we employ machine-learning-based random forest analyses and describe 11 acoustically distinguishable call types. We discuss issues associated with resolving vocal repertoires from wild data in great apes and highlight potential future approaches to further capture the complexity of the bonobo vocal system.

animal behavior and cognition↗

bioRxiv2024

Predictability of next elements in chimpanzee gesture sequences

Recent research has produced evidence for basic combinatorial abilities in the vocal systems of different animal species. Here, we investigate the structure of gesture sequences in Eastern chimpanzees (Pan troglodytes schweinfurthii) to detect whether gestural communication shows non-random combinations and how combinatorial rules influence predictability. Gesture, as compared to vocalization, offers greater flexibility in how signals are combined--for example overlapping in time -- and as the parsing of signals into sequences is dependent on researcher decisions, we employ a multiverse approach, considering four different definitions of what constitutes a sequence based on varying time thresholds. Our results indicate that sequences tend to be short (even with the most liberal time-window) and that transitions between some gesture types occur more frequently than expected by chance, with some transitions showing significant association across all time-windows. These transitions often involve repetition, suggesting persistence as a key aspect of chimpanzee gestural sequences. Information about previous gestures reduced uncertainty in predicting subsequent gestures. The order of gestures within sequences appears to be less critical than their cooccurrence, challenging assumptions based on the linear patterning derived from vocal communication. Our findings highlight the importance of methodological choices in sequence definition and suggest that chimpanzee gestural communication is characterised by a mix of predictability and flexibility, with implications for understanding the evolution of complex communication systems.

animal behavior and cognition↗

bioRxiv2023

Vocal-visual combinations in wild chimpanzees

Human communication is strikingly multi-modal, relying on vocal utterances combined with visual gestures, facial expressions and more. Recent efforts to describe multi-modal signal production in our ape relatives have shed important light on the evolutionary trajectory of this core hallmark of human language. However, whilst promising, a systematic quantification of primate signal production which filters out random combinations produced across modalities is currently lacking. Here, through recording the communicative behaviour of wild chimpanzees from the Kibale forest, Uganda we address this issue and generate the first repertoire of non-random combined vocal and visual components. Using collocation analysis, we identify more than 100 vocal-visual combinations which occur more frequently than expected by chance. We also probe how multi-modal production varies in the population, finding no differences between individuals as a function of age, sex or rank. The number of visual components exhibited alongside vocalizations was, however, associated with vocalization type and duration. We demonstrate that chimpanzees produce a vast array of combined vocal and visual components, exhibiting a hitherto underappreciated level of combinatorial complexity. We conclude that a multi-modal approach is crucial to accurately representing the communicative abilities of non-human primates.

animal behavior and cognition↗

bioRxiv2021

From collocations to call-ocations: using linguistic methods to quantify animal call combinations

Emerging data in a range of non-human animal species have highlighted a latent ability to combine certain pre-existing calls together into larger structures. Currently, however, there exists no objective quantification of call combinations. This is problematic because animal calls can co-occur with one another simply through chance alone. One common approach applied in language sciences to identify recurrent word combinations is collocation analysis. Through comparing the co-occurrence of two words with how each word combines with other words within a corpus, collocation analysis can highlight above chance, two-word combinations. Here, we demonstrate how this approach can also be applied to non-human animal communication systems by implementing it on a pseudo dataset. We argue collocation analysis represents a promising tool for identifying non-random, communicatively relevant call combinations in animals.

animal behavior and cognition↗