This post continues my summary of Jim Hurford’s discussion of two contrasting extreme positions on language evolution in his plenary talk at the Poznan Linguistic Meeting. Here’s the summary of these two positions from my last post:
(1) There was a single biological mutation which (2) created a new unique cognitive domain, which then (3) immediately enabled the “unlimited command of complex structures via the computational operation of merge. (4) This domain is used primarily for advanced private thought and only derivatively for public communication. (5) It was not promoted by natural selection.
(1) There were many cumulative mutations which (2) allowed the expanding interactions of pre-existing cognitive domains creating a new domain, which however is not characterized by principles unique to language. This then (3) gradually enabled the command of successively more complex structures. Also, on this view, this capacity was used primarily for public communication, and only derivatively for advanced private thought and was (5) promoted by natural selection.
Hurford criticized the position that the biological changes enabling languages primarily evolved for private thought, because this would imply that the first species in the Homo lineage that developed the capacity for unlimited combinatorial private thought (i.e. “merge”) were non-social and isolated clever hominids. This, as Hurford rightly points out, is quite unrealistic given everything we know about human evolution regarding, for example, competition, group size, neocortex side and tactical deception. There is in fact very strong evidence that what characterizes humans the most is the exact opposite as would be predicted by the “Merge developed in the service of enhancing private thought” position: We have the largest group size of any primate, the largest neocortex (which has been linked to the affordances of navigating a complex social world) and have the most pronounced capacity for tactical deception.
In terms of the timing of externalization and the evolution of merge there are two possibilities:
Externalization preceding Merge: On this view, even the simplest conceptual units were externalized from an early stage in hominid evolution onwards (confer Bickerton’s protolanguage). This means that merge would have been public from the start.
The other possibility is that the capacity to merge conceptual units for advanced thought precedes externalization and public communication.
In normal humans it is important to note that complex thought and complex language go together. There are of course pathologies where they are dissociated but overall there is a lot of evidence that there is a correlation between verbal and noverbal IQ, that learning simple public labels modifies thought, especially in children, that bilinguals perform better in certain tasks, and that words can function as and aid to thought.
This suggests a less simple possibility: A coevolutionary spiral of successively more complex language and more complex thought.
This also means there can’t have been only a single mutation: The grammatical system and the system supporting it (storage capacities, working memory, vocal manual skills, pragmatics, etc.) are highly interdependent. They all had to evolve in partnership.
Hurford closed his talk by discussing the question whether evolution has produced a new unique domain. Hurford stresses that our evolved capacities for language have built on pre-existing capacities for, e.g.
- Hierarchical organization of behaviour
- Semantic memory for facts storage
- Fast routinization of useful procedures
However, he holds that our language capacities go well beyond these pre-existing capacities, which seems for him indicates that evolution has in fact created a new unique domain. This goes against, for example Ray Jackendoff’s view, who holds that:
“So the conclusion is mixed: The wondrous recursive creativity in language is not as special as it is often claimed to be. Nevertheless language is a special system because of what is does and the particular structural materials it uses to do it” (Jackendoff 2007: 143, see also Hurford 2011: 510 ).
Beckner et al. (2009: 17), in their position paper on language as a complex adaptive system, go even further:
“[I]n a complex systems framework, language is viewed as an extension of numerous domain-general cognitive capacities such as shared attention, imitation, sequential learning, chunking, and categorization (Bybee, 1998b; Ellis, 1996). Language is emergent from ongoing human social interactions, and its structure is fundamentally molded by the preexisting cognitive abilities, processing idiosyncrasies and limitations, and general and speciﬁc conceptual circuitry of the human brain.”
According to them
“As soon as humans were able to string two words together, the potential for the development of grammar exists, with no further mechanisms other than sequential processing, categorization, conventionalization, and inference-making (Bybee, 1998b; Heine & Kuteva,2007).”
As a Cognitive Linguist I think that regarding this last point I agree more with Jackendoff and Beckner et al. than with Hurford, although this might also only be a terminology issue of how to define “new” or “unique.” I think it’s perfectly fine to say that the system supporting language becomes a specialized and unique domain due to the kinds of symbolic input it operates on, but many developmentalists would also stress that it is in fact not evolution which created this new unique domain, but ontogeny in a richly socio-interactive cultural setting or a “symbolic niche.” Saying that in normal modern language users’ there is a specialized system for language is quite compatible with Cognitive Approaches and the view of language as a complex adaptive system. However, as people like Elizabeth Bates or Anna Karmiloff-Smith have pointed out, a linguistic cognitive domain can emerge through multiple domain-general cognitive and processing factors in combination with dynamics of social interaction and actual language during a child’s individual development. So in this view it would not be evolution creating a new unique domain, but development, which is quite compatible with what we know about neural re-use:
“According to [theories of neural re-use], it is quite common for neural circuits established for one purpose to be exapted (exploited, recycled, redeployed) during evolution or normal development (my emphasis), and be put to different uses, often without losing their original functions. Neural reuse theories thus differ from the usual understanding of the role of neural plasticity (which is, after all, a kind of reuse) in brain organization along the following lines: According to neural reuse, circuits can continue to acquire new uses after an initial or original function is established; the acquisition of new uses need not involve unusual circumstances such as injury or loss of established function; and the acquisition of a new use need not involve (much) local change to circuit structure (e.g., it might involve only the establishment of functional connections to new neural partners)” (Anderson 2010)
In this perspective language was shaped by and adapted to the organization principles brain, and it is normal development and the connectivity patterns. Language, then, becomes more similar to other highly specialized neural systems like chess or driving (Karmiloff-Smith 1992). Thus, general cognitive capacities and constraints (e.g. constraints from the conceptual system, pragmatics, learning and processing mechanisms, perceptuo-motor factors and others, cf. Christiansen & Chater, 2008) and their interconnectivity might play a more crucial role than Hurford gives them credit for.
As Michael Tomasello (2003: 284) argues:
“Everyone agrees that human beings can acquire a natural language only because they are biologically prepared to do so and only because they are exposed other people in the culture speak- ing a language. The difficult part is in specifying the exact nature of this biological preparation, including the exact nature of the cognitive and learning skills that children use during ontogeny to acquire competence with the language into which they are born.”
So the jury is still out whether the interconnection and co-optation of domain-general processes alone can explain language acquisition and use, and this is a highly active and exciting area of research (see e.g. this paper published a couple of months ago in a special issue on “Pattern perception and computational complexity“) that plays a fundamental role in answering the question of what is wrong, and what is right in language evolution research.