Hey mate? There is a snake!

Chimpanzee Alarm Call Production Meets Key Criteria for Intentionality

Determining the intentionality of primate communication is vital to understanding the evolution of human language. Although intentional signalling has been studied for some great ape gestures, comparable evidence is currently lacking for their vocal signals.

In this study the following criteria were used to analyse if the Sonso group of chimpanzees in the Budongo Forest in Uganda were communicating with intention.

criteria for intentionality in chimp comms







The researchers presented the chimpanzees with a python model with up to 4 observers recording the calls and behaviours of each focal individual.

chimp intent calls diagram








Figure – The snake image represents the location of the python
model, concealed by leaves. Observers and their main roles are defined. The
chimpanzee image depicts the focal chimpanzee, who could be accompanied by
other group members depending on the experimental condition.

The results of this study indicate that some chimpanzee calls meet the criteria for intentionality, for example most chimpanzees who had seen the snake model gave calls and demonstrated gaze alternation and audience checking with a fellow chimpanzee. ‘Waa Barks’ (WB) and ‘Alarm Huus’(AH) were produced in the presence of socially important individuals who had not seen the snake. Furthermore , WB’s and AH’s were increased in the presence of friends vs. non-friends.

The researchers believe that their findings disagree with the gestural theories of language origins and instead support a multimodal origin for human language.

Video illustrating gaze alternation and looking at a group member before producing waa barks. Video is filmed from position 2. Focal adult female Nambi reacts to the arrival of her adult son Musa by turning and looking at Musa before producing her first waa barks of the trial. Nambi then looks immediately back at the snake, showing gaze alternation between the recipient and the snake whilst calling. During Nambi’s waa bark production, Musa stands bipedally.


Schel, AM., Townsend,SW.,Machanda, Z.,Zuberbuhler, K., and Slocombe, KE. (2013). Chimpanzee Alarm Call Production Meets Key Criteria for Intentionality. PLoS ONE 8 (10): DOI: 10.1371/journal.pone.0076674



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