Since the 1960s, a handful of high-profile research projects have taught captive chimpanzees to use sign language or symbol systems to communicate with human researchers — some of the most famous, and most debated, studies in animal cognition research.
Early sign language research with chimpanzees, beginning in the 1960s, aimed to test whether a non-human species could learn a human-style communication system, given that chimpanzees' vocal anatomy makes spoken language physically impossible for them. Researchers instead taught chimpanzees a modified version of sign language, and several individuals learned to use dozens, and in some cases hundreds, of signs to request items, describe objects, and answer simple questions.
Chimpanzees in these studies learned to combine signs meaningfully — for instance, inventing novel combinations to describe unfamiliar objects — and to use signs spontaneously in appropriate contexts, not just in response to direct prompting. Some individuals also appeared to teach signs to other chimpanzees they interacted with, suggesting a degree of social transmission beyond simple human-directed training.
Critics have pointed out important limitations: chimpanzees' sign combinations rarely showed the recursive grammar that defines human language, researchers sometimes unintentionally cued responses, and much of the interpretation of "conversations" relied on generous readings by invested trainers. Most researchers today agree chimpanzees demonstrated genuine referential communication and symbol use, but not full human-equivalent language.
Alongside sign language, researchers have used symbol boards and touchscreen systems to study chimpanzee communication and cognition, avoiding some of the interpretation challenges of hand signs. These studies have reinforced similar conclusions: chimpanzees can learn to use abstract symbols meaningfully and intentionally, representing a genuine, if limited, communicative capacity beyond simple instinctive signalling.
In the wild, chimpanzees don't use sign language, of course — they rely on a rich combination of vocal calls, facial expressions, gestures, and posture, all shown to be flexible and context-dependent rather than fixed, instinctive signals. Some researchers argue wild chimpanzee gestural communication may be a closer, more naturalistic parallel to what the sign language studies were trying to access artificially.
Beyond scientific curiosity, these studies fundamentally shifted how researchers and the public think about animal cognition, demonstrating that a non-human species could grasp and use abstract, referential symbols — a capacity once assumed to be uniquely human. That shift in understanding underpins much of the modern case for taking great ape welfare and conservation seriously.
Understanding just how cognitively and communicatively sophisticated chimpanzees are reinforces why sustained, serious field research matters — including the kind of long-term, patient daily observation the Bulindi Chimpanzee & Community Project carries out with its wild community in Western Uganda. Understanding a specific wild population's communication and behaviour in detail depends on exactly this kind of long-term, consistent field presence.
Are any sign-language-trained chimpanzees still alive today? Some individuals from these historic research programmes have lived into old age in sanctuary care, though active new sign-language training research has become less common as the field has shifted toward other research methods.
Do wild chimpanzees ever use anything resembling sign language? Not sign language specifically, but wild chimpanzees do use an extensive natural gestural repertoire — reaching, touching, and other hand and arm signals — as part of their everyday communication.
Could chimpanzees learn to speak with training? No — chimpanzee vocal anatomy physically cannot produce the range of sounds required for human speech, which is precisely why sign language and symbol-based studies were developed as alternatives.
These landmark studies reshaped how seriously scientists — and the public — take animal communication and cognition generally, reinforcing the case that chimpanzee welfare and conservation deserve the same rigour and seriousness once reserved almost exclusively for uniquely human concerns. These studies also sparked broader ethical debate about captive great ape research generally, contributing directly to stricter modern standards around consent, welfare, and appropriate research design that now govern how such studies, where they still occur, are actually conducted. Documentary filmmakers have returned to this research repeatedly over the decades, both to showcase the genuinely striking findings and, more recently, to explore the more complicated ethical legacy of some of the original research programmes and how the individual chimpanzees involved fared afterward.
Contemporary researchers generally view this era of study as a foundational, if imperfect, first step — one that opened the door to the more naturalistic, field-based communication research that continues today.
Support the Bulindi Chimpanzee & Community Project to help fund that ongoing field research and habitat protection. Modern primate cognition research has largely moved on to less invasive, more naturalistic methods, though the foundational insight from these original studies — that chimpanzees can use symbols meaningfully — remains broadly accepted today.