The Linguistics of the Rock Hyrax Language
The “Law of Brevity” in animal communication
Searching for the origins of human language, we often look for similarities with animal communication. Beyond the existing parallels in sound-producing mechanisms, there are also statistical principles related to production and communicational efficiency. One of these principles is the "Law of Brevity", which states that there is an inverse relationship between word length and usage that optimizes informational coding against the effort of producing sounds. For example, the common usage of short words, rather than long, multiple syllable words (e.g., encyclopedia, association).
Although the Law of Brevity is central to human language, its validity regarding animal communication is controversial. This may be due to the difference in the way humans and animals produce sound, as well as the variations in the vocal repertoire of males versus females, which are often present in animals.
This study, conducted by Dr. Amiyaal Ilany's laboratory in the Goodman Faculty of Life Sciences, examined sex-specific differences in vocal repertoire and communicative efficiency of the rock hyrax, a mammal in which females are usually much more social than males. Unique sex-specific differences were found in the hyrax vocal repertoire. Females have an extensive vocal repertoire with more affiliative call types than the males. The bachelor male repertoire, which includes male-specific "advertisement" songs, is more in line with linguistic efficiency laws – but in a special version.
The hyrax vocal repertoire does not adhere to the classic linguistic patterns mentioned above that relate to the call length and frequency of their use, but rather shows a negative relationship between call amplitude and usage, suggesting amplitude as the dominant factor in shaping the effectiveness of communication in wildlife – unlike humans, where the main factor is the word length.
Those differences might be related to signaling distance, as human language is mostly intended for short-range communication while among animals, long-range, high-amplitude calling is common. Thus, the differences between the communication requirements of humans and animals might have resulted in the efficiency of information coding, which has been influenced by different evolutionary forces.
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