Functionally referential signals — vocalizations that reliably inform listeners about specific external events or objects — have long fascinated comparative psychologists because they blur the boundary between animal communication and human language. Vervet monkeys emit distinct alarm calls for leopards, eagles and snakes, and recipients respond appropriately to each. Prairie dogs embed information about predator features in their calls, and some birds encode details about food quality. But the question of just how fine-grained these references can be has remained open. Most documented referential systems distinguish broad categories: predator versus non-predator, high-value versus low-value food. Whether a signal can pick out individual food types within a category — whether a chimp’s grunt for bread sounds meaningfully different from its grunt for mango — had never been empirically tested for chimpanzee food calls.

Chimpanzees produce rough grunts when finding and eating food, and earlier work had established that the acoustic structure of these calls varies with the preference value of the food that elicits them. Grunts given to highly preferred foods differ systematically from those given to less desirable items, and subsequent research showed that listening chimpanzees can use this variation to guide their own foraging decisions. That established a meaningful baseline: the calls encode relative preference. What remained unknown was whether the specificity stopped there. If two foods are both highly preferred — say, bread and mango — do the grunts they elicit sound the same to a listener, or do they carry information distinguishing one food from the other? And critically, does that fine-grained information actually matter to receivers, or is it merely acoustic noise that no chimpanzee attends to?

To answer these questions, the research team, whose work was supported by the Biotechnology and Biological Sciences Research Council and by the Swiss National Science Foundation through the NCCR Evolving Language programme, combined two complementary approaches. The first was a careful acoustic analysis of food calls recorded from chimpanzees at the Wolfgang Köhler Primate Research Centre in Leipzig, Germany, where calls elicited by foods of matched preference values could be compared. The second was a playback experiment — a technique in which recorded vocalizations are broadcast to an animal while researchers observe how it responds — allowing the team to test whether the acoustic distinctions they detected were actually meaningful to a listening chimpanzee rather than incidental by-products of arousal.

The acoustic analysis produced a strikingly layered picture. The calls differed between foods of high and low preference value, replicating and extending the earlier findings that grunts track how much a caller likes what it has found. But the analysis went further: significant acoustic differences also emerged between individual food types within each of those preference categories. In other words, grunts elicited by different high-value foods could be statistically discriminated from one another, and so could grunts elicited by different low-value foods. The calls were not simply graded along a single dimension of excitement. Instead, they appeared to encode at least two distinct dimensions of information simultaneously — the general value of the food and its specific identity — a combination that suggests a far richer encoding system than anyone had demonstrated in chimpanzee feeding vocalizations.

Statistically detectable differences, however, do not automatically translate into communicative relevance. An acoustic signature can reflect physiological differences in arousal, jaw position, or food texture in the mouth without any listener ever extracting information from it. This is where the playback design proved decisive. The researchers broadcast recorded food calls to a chimpanzee subject and measured the responses, focusing on whether the animal’s behaviour indicated that it had interpreted the calls as information about what lay hidden at the playback location. By pairing calls recorded in one context with search opportunities in another, the experiment isolated the informational content of the vocalization itself from any direct sensory experience of the food.

The results were remarkable on all three fronts. The listening chimpanzee discriminated between calls elicited by high-value and low-value foods, confirming once again that preference information is accessible to receivers. More importantly, the subject also discriminated between calls elicited by individual types of high-value food, and between calls elicited by individual types of low-value food. The fine-grained distinctions that showed up in the acoustic analysis were not lost on the audience: the receiver behaved as though it knew not just that something good had been found, but what kind of good thing it was. This represents, the authors write, an unprecedented degree of specificity in the referential food calls of our closest living relatives — a level of detail previously identified only in alarm call systems, not in feeding vocalizations.

The theoretical implications ripple outward in several directions. For theories of language evolution, the finding narrows the perceived gap between primate vocal communication and human speech. One cornerstone of linguistic meaning is the ability of a signal to pick out specific referents rather than broad emotional states, and this study shows that chimpanzee calls can do something analogous with food types, not just food categories. It also challenges the long-standing division between ‘referential’ alarm calls and ’emotional’ food calls: if food calls encode specific identities in a way receivers use, the referential-emotional dichotomy looks increasingly like a human-imposed simplification rather than a real feature of chimpanzee communication. The study adds to a growing body of evidence that the vocal repertoire of great apes is far more structured than the behaviorist traditions of the twentieth century assumed.

The methodology deserves attention too. Combining acoustic analysis with playback experiments is the gold standard for demonstrating functional reference, because each approach compensates for the other’s weaknesses. Acoustic analysis can reveal structure that receivers ignore; playback can reveal comprehension of differences the analysis missed. By requiring both — statistically discriminable calls and demonstrably different receiver responses — the researchers built a case that is difficult to dismiss. The work was approved by the School of Psychology Ethics committee at the University of St Andrews, and the authors declare no competing interests. The study was published open access, with a citable, permanent DOI, meaning anyone can examine the evidence in full.

Questions naturally remain. The playback tested a single subject, so the generality of comprehension across individuals and communities will need confirmation. It is also unclear how the specificity arises — whether callers intentionally vary their grunts to inform others, whether the acoustic differences emerge as side effects of eating different foods, or whether listeners have simply learned to exploit regularities in the sounds. None of this diminishes the central result: chimpanzees listening to a distant group member’s grunts can apparently learn both how desirable a hidden food is and what that food actually is. For a species separated from our own lineage by roughly six million years, that is a strikingly sophisticated channel of information, and it suggests that the seeds of referential specificity run far deeper in the primate lineage than the study of alarm calls alone had ever revealed.

Subject of Research: Referential specificity of chimpanzee food calls tested through acoustic analysis and playback experiments

Article Title: Chimpanzee food calls provide information about the value and type of food: a playback study

Article References: Watson, S. K., Kaller, T., Cheng, L., Wathan, J., Townsend, S. W., Zuberbühler, K., Call, J., & Slocombe, K. E. (2026). Chimpanzee food calls provide information about the value and type of food: a playback study. Animal Cognition. https://doi.org/10.1007/s10071-026-02105-w

Image Credits: AI Generated

DOI: 10.1007/s10071-026-02105-w

Keywords: chimpanzees, food calls, functional reference, rough grunts, playback experiment, vocal communication, animal cognition, primatology, language evolution, acoustic analysis, foraging behaviour, referential signalling

For decades, linguists have theorized that language change is primarily a generational phenomenon, necessitating the gradual phasing out of older speakers in favor of new cohorts who shape contemporary vocabulary and meanings. This study, however, challenges this dogma by showing that semantic evolution does not solely hinge on generational turnover. Instead, semantic innovations percolate through a complex social matrix involving active engagement from speakers of all ages — a revelation with profound implications for our understanding of language dynamics.

The research team, headed by Gaurav Kamath, a doctoral candidate in McGill’s Department of Linguistics, applied sophisticated AI models to an unprecedentedly rich corpus: over 7.9 million speeches delivered by thousands of U.S. Congress members spanning nearly a century and a half, from 1873 to 2010. This massive dataset enabled the researchers to trace linguistic trajectories over time with remarkable granularity, uncovering subtle semantic shifts that had previously eluded detection through traditional linguistic methodologies.

One of the primary methodological challenges faced by the team was the pinpointing of emergent meanings of words in real time. While identifying the precise moment a new semantic value arises is inherently difficult due to the gradual and often sporadic nature of adoption, the researchers circumvented this obstacle by focusing on meanings once firmly established. Through a retrospective approach, they mapped how and when these newer interpretations first materialized and subsequently diffused across speaker demographics.

A quintessential example cited in the study is the term “article.” Between 1873 and 2010, “article” retained a stable meaning in legislative contexts—specifically as a constituent part of bills or laws. However, the word exhibited a semantic evolution in other domains: its usage to denote physical objects was prevalent well into the 1940s but began to wane by the mid-20th century. By the 1970s, “article” had largely come to signify a journalistic piece, highlighting how meanings can diverge and resettle within cultural milieus over extended temporal frames.

Beyond linguistic intricacies, the findings hold significant sociolinguistic import. The study reveals that older speakers, traditionally viewed as resistant to linguistic innovation, often adopt new semantic uses within only two or three years after younger speakers, narrowing the generational lag previously assumed to be far larger. In some noteworthy cases, older individuals even initiate semantic shifts, challenging stereotypes about age and language adaptability.

The implications of these discoveries extend well beyond the legislative setting in which the data was gathered. Since congresspeople constitute a relatively homogenous and socially elite group, the researchers emphasize the necessity of applying similar analytical frameworks to more demographically and culturally diverse populations. Such expanded research would test whether the patterns observed in the halls of Congress translate to everyday language use in broader social contexts, encompassing varied ethnicities, socioeconomic statuses, and age brackets.

The methodological innovation in this study lies primarily in the deployment of cutting-edge AI tools capable of semantic content analysis on an enormous scale. This approach surpasses traditional qualitative assessments, facilitating the identification of subtle patterns across millions of data points and the visualization of how these shifts propagate through individual speaker histories. The integration of AI thus provides a powerful new lens for studying language change, bridging computational linguistics with social science inquiry.

Moreover, the researchers query whether these techniques could eventually forecast the uptake of contemporary slang and emergent lexical trends among today’s youth. Predicting such phenomena would not only enrich linguistic theory but could have practical applications in fields ranging from marketing to education and technology development, where understanding the pulse of language innovation is crucial.

Speaking on the study’s broader significance, Morgan Sonderegger, an associate professor at McGill and co-author on the paper, remarked on the complexity of language evolution as a social process. He underscored that while their findings defy simplified generational paradigms, much remains to be explored about the diverse ways communities engage with language innovation. Continued research, leveraging data from multifaceted social networks and communication platforms, promises to deepen insights into how humans negotiate meaning over time.

The study, titled “Semantic Change in Adults is Not Primarily a Generational Phenomenon,” was published in the esteemed journal Proceedings of the National Academy of Sciences (PNAS) on July 28, 2025. The work received partial funding from the Fonds de Recherche du Québec – Société et Culture, underscoring the importance of supporting interdisciplinary research at the intersection of linguistics, social science, and technology.

As language constantly morphs in response to societal shifts, digital communication, and cultural trends, understanding the mechanisms of semantic change is crucial. This research not only challenges existing theoretical frameworks but also exemplifies the potential for AI to unlock new vistas in the study of language. In doing so, it broadens our grasp of human communication, emphasizing that language is a living, collective enterprise shaped by speakers of all ages working together to define and redefine meaning.

This paradigm-shifting study thus invites linguists, social scientists, and technologists alike to reconsider the interplay between age, innovation, and language evolution, opening the door to future explorations that may redefine how we think about the words we use and the meanings we share.

Subject of Research: People

Article Title: Semantic change in adults is not primarily a generational phenomenon

News Publication Date: 28-Jul-2025

Web References:

• https://doi.org/10.1073/pnas.2426815122

References:
Kamath, G., et al. (2025). Semantic Change in Adults is Not Primarily a Generational Phenomenon. Proceedings of the National Academy of Sciences of America.

Keywords: Linguistics, Semantic Change, Language Evolution, Social Sciences, Computational Linguistics, AI, Language Adoption