鳥類の音声活動

記号論的考察

抄録

Though numerous references have so far been made to the song of bird, no systematic treatment ever appeared with a view to incorporating it intothe theory of ‘phylogenesis’ of human language.
The author stresses, in this article, the significance of this kind of approachin elucidating the structural relationship between human languageand vocal communication in bird. In this connexion, he pays special attentionto the habit of sound learning commonly possessed by man and bird.
After presenting a sketchy review of vocal behaviour in Ayes, of whichthree types are to be distinguished, namely, 1) call-note, 2) song par excellenceincluding love and territory song and 3) joy song, he tries to showthe configurational nature of stimuli birds react to in the visual as well asin the auditory field.
For example, gallinaceous birds usually react to flying birds of prey bygiving alarm call. Tests using models of flying birds showed that ‘as longas a model had a short-neck, the experimental birds would show alarm.’Further experiments revealed that ‘it is not the shape as such that actedas a sign stimulus, but shape in relation to direction of movement.’ Suchstrict dependence of an innate reaction on a certain set of sign stimulimakes us postulate, in the mind of animals, the Innate Releasing Mechanismwhich is, to use the metaphor of Konrad Lorenz, the appropriate key-hole matched to the shape of a key.
When this concept of ‘key’ is applied to the interspecific reactions, theset of essential stimuli above explained is just what we now call a (social) releaser.
The author then introduces the idea of ‘reaction chain’ which consistsof ‘a chain of separate reactions each of which is dependent on a specialset of sign stimuli.’ And each of these stands in a special causal relationto the preceding one. Thus the reaction chain can be looked upon as ahighly specialized combination of releasers. Here he points out that sincereleasers used in reaction chain do elicit appropriate responses only whenused in a definite order peculiar to each species of animals, we mightrecognize here a sort of ‘syntax’ existing between these signs (i.e.releasers). In other words, these signs do not behave as signs unless theyare put in a structural order.
Descriptions of mating behaviour in bird abound in the so-called ‘rituals’performed by male and female. These precoital rituals, in whichsong also plays an important role, are nothing but the sort of syntacticcombination of signs just referred to.
As compared with song proper just analysed, call-note, which seemsabout the only vocal activity most students in this field take into consideration, presents quite a different picture. In the author's opinion, a callnote is a vocal sign used empractically, to use the terminology of KarlBuhler. It is employed, as it were, in the capacity of diakritikon andrequires no specific structural context of its own. On the other hand, closer examination of joy song reveals that vocal behaviour in general is, by its very nature, apt to free itself from strict dependence on the situationalconditions. This tendency observed in bird, together with the capacityto learn diverse sounds, is, the author maintains, perhaps countedupon as one of the prerequisites needed for the emancipation of sign from‘concrete things’.
From these considerations, the author concludes that semiotic analysisof bird song discloses striking similarity obtaining between vocal communicationin bird and human language, and thus helps us to open a new perspective in the theory of signs.