Compositionality
Trained non-human primates learn to combine form–meaning pairings fairly early. The chimpanzee Washoe began combining signs after only 10 months of training, Moja at the age of six months, and the gorilla Koko is reported to have begun using sign combinations after four months of sign language training (Miles 1978: 105).
Can animals combine form–meaning pairings with each pairing retaining its meaning constant? Do they understand that utterances can be broken up into concepts and can be combined productively and in a principled way, and are they able to use at least two paradigms of linguistic forms productively in a sequence? With the term compositionality (or combinatorics) we refer to the fact that linguistic forms are, first, combinatorial, in that the meaning of forms remains stable across contexts: Meaningful units can be combined and still retain their semantic integrity—that is, combining is compositional, even if the meaning may be influenced by the context in which it occurs (for example, the form big as in a big problem does not have exactly the same meaning as in a big car). Second, we also use the term for the ability to productively combine novel forms and concepts.
There is fairly clear evidence that the apes that were studied as well as Alex, the grey parrot, and the two bottle-nosed dolphins, have the ability for discrete combinatorics. For Alex, for example, the expression rose paper refers to paper with the property of being colored rose, not to something intermediate between rose and paper; for Kanzi, the bonobo, the expression Tickle ball, meaning to tickle him by rubbing the ball all over his body, was perceived as consisting of two distinct units rather than of one unanalyzed entity, as is suggested by his ability to re-combine these units, and the bottle-nosed dolphins interpreted PIPE TAIL-TOUCH as a command to perform an action on an object, that is, as an expression consisting of two discrete entities (see Kako 1999: 6).
We noted above that Zuberbühler (2002) found that wild Diana monkeys (Cercopithecus Diana) in the Ivory Coast appear to have a combinatory rule that is not only suggestive of a concatenation of form–meaning pairings but also of a grammatical function. Male Campbell monkeys (Cercopithecus campbelli) have distinct alarm calls for leopards and for crowned-hawk eagles, and when hearing these calls, Diana monkeys respond with their own corresponding alarm calls. In addition, Campbell monkeys have a third call, consisting of a pair of low, resounding ‘‘boom’’ calls, which is used for disturbances that are not a direct threat, such as a falling tree, or a distant predator. Once Diana monkeys hear a sequence of the two calls of Campbell males, they ignore the alarm meaning. Note, however, that this sequence of two calls is not—and cannot be—productive since there are no other form–meaning pairings to which it could be applied.
A noteworthy ability is documented for the trained grey parrot Alex, who ‘‘recombines beginnings and ends of existent labels, rather than ends with ends or beginnings with beginnings. Thus there are utterances such as ‘‘banacker’’ (banana-cracker), but never ‘‘bancrack’’ or ‘‘ana-er’’. The meaning of the use of this behavior is unclear but suggests, as Pepperberg (1999a: 17) argues, some sensitivity to internal order and subunit structure that is not necessarily expected in non-humans.
