I feel that language is one of (probably the most) important difference between humans and other animals. This post is not an attempt to downgrade the importance of language. But if we do not notice the limits of its importance then we cannot understand all the language-less animals. Language is not the only vehicle for many aspects of thought. Many assume that without language it is impossible to think, to remember, to communicate, to have categories/plans/procedures, to have culture and to even have consciousness. Slowly it is being shown that other animals can do many of the things that used to be classed as only-with-language skills. We just do them more effectively with language.
In a recent paper (Jennifer Vonk. Matching based on biological categories in Orangutans (Pongo abelii) and a Gorilla (Gorilla gorilla gorilla). PeerJ, 2013; 1: e158 DOI: 10.7717/peerj.158) it was shown that apes could put pictures of animals into categories that relied on more than close visual resemblance. The apes used the type of categories that we use in language and in science. They did not need the use of language to construct these categories. This is just the latest in a long string of reports which show animals doing various types of cognition that were once thought only possible in humans because of human language and consciousness.
It seems obvious that musical composers think when composing and that they think in musical not semantic ideas. Sculptors think but not in words but in three dimensional shapes. Athletes, for instance soccer players, think but they think kinetically. In fact they often do not have the time to think in words and ‘choke’ when they try. In cases like these it may be possible (it also may not) to document in words the processes that ended in a tune, a statue, or a scoring goal but that is not relevant – it is not how the process actually happened but just a not very accurate description of it.
We do not need language for some thinking. What we need is a working model of the world in which what-if scenarios can be played out. It does not have to be the whole world but one in which we can hear or see or feel causal chains. There is no reason to assume that animals cannot think quite sophisticated thoughts in this sensory-motor non-symbolic way. There is also no reason why they cannot think symbolically, just in wordless concepts. They communicate with each other. They seem to have episodic memory and therefore would have conscious experiences to remember. It would be wise to assume that the highly social mammals, especially primates, have basically the same cognitive apparatus as ourselves and that all vertebrates are similar in the general way the brain works.