Generalization, or rather some development that is a kind of succession of generalization occurs within three stages that can conveniently be labelled accord, competition, and dominance. In the first stage, visual and auditory cues are in agreement. (Indeed at the earliest stage the auditory cues may be presumed to be those incidentally produced in normal interactions with the particular objects in question, and the latest stage under consideration may still be only one that imitates those sounds.) At this stage the synaptic structures (apart from the purely auditory ones) excited by vocalizations are those that would be excited by particular visual stimulations.
At the competition stage, a discrepancy emerges between visual synaptic structures and auditory synaptic structures. One can be exposed to auditory cues without its usual visual associations. This does not mean that other visual cues are not present while these auditory cues are occurring. These new visual cues set up new contextual information while the auditory cues set up a past context. As the new context is resolved synaptically, the non-auditory perceptual cues are accommodated through auditory synaptic structures, as new associations, and are carried into future context. As such, auditory cues tend to dominate, since they can be processed in the absence of visual or other perceptual cues. However, the dominance of auditory cues do not match accurately any synaptic structures that could be excited visually. We usually do not have a specific image when fruit is uttered, certainly not images of hybrid bananas and apples. These auditory structures in hominids are not linguistic, but the dominance of auditory structures over other perceptual structures may eventually give rise to a functionalization of vocalization that has eventually produced linguistic noises.
Auditory cues are not solely noises but also stimulate synaptic structures involving other perceptual cues. The dominance of auditory cues occur because they can be shared in the absence of indexical cues. Though they are initially shaped from indexical cues, the process of competition endows auditory cues with independent capacities. Competition leads to a generalization in which perceptual structures are synaptically stimulated despite the absence of indexical cues. In imitating indexical cues, auditory cues can stimulate synaptic structures that can loosely encompass perceptual structures that originally would be stimulated in the presence of indexical cues. As such, auditory cues can free perceptual structures from indexical constraints. The incidental effect of such generalization is exploited and give auditory cues an independence from specific perceptual structures.
It is that independence that somehow enables the accommodation of other non-shared perceptual structures, structures that help define the elusive aspects of vocal cues that make them more than noises. Further generalization occur when incidental effects, generated from the independence of auditory cues, give rise to new classes of physical types, usually higher-order physical types. These new objects are used to produce certain effects on demand. They can also be used to perform different functions, functions that stray from original constructs.
The process of generalization can describe the emergence of vocables from non-vocables, because the emergence of new physical types happens from a change in the accommodation of some synaptic structures. Because new physical types are usually of higher order, they can accommodate a larger array of synaptic structures. The accommodation of certain structures will lead to changes in function which in turn will give rise to new physical types. Auditory cues may have occurred naturally as a process of exertion, but the repetition of auditory cues on demand to produce specific effects has led to a shared phenomenon between members of a species. This phenomenon may not have, at first, been linguistic, and produced effects might have relied heavily on prosodic features, but through the process of generalization, vocables have appeared as new classes of physical types.