Children are better than adults at learning second languages. Children find it easy, can do it implicitly and achieve a native-like competence. However, as we get older we find learning a new language difficult, we need explicit teaching and find some aspects difficult to master such as grammar and pronunciation. What is the reason for this? The foremost theories suggest it is linked to memory constraints (Paradis, 2004; Ullman, 2005). Children find it easy to incorporate knowledge into procedural memory – memory that encodes procedures and motor skills and has been linked to grammar, morphology and pronunciation. Procedural memory atrophies in adults, but they develop good declarative memory – memory that stores facts and is used for retrieving lexical items. This seems to explain the difference between adults and children in second language learning. However, this is a proximate explanation. What about the ultimate explanation about why languages are like this?
In the last post, I discussed some of the literature into experimental communication, with the intention of then following it up by looking at recent experiments done at Edinburgh (and beyond). But as Hannah pipped me to the post, with a great overview of the wide range of experiments into language evolution, I’ll instead limit this to two relatively recent papers on Human Iterated Learning (Kirby et al., 2008; Cornish et al., 2009)
Drawing from experimental approaches found in Diffusion Chain and Artificial Language Learning studies, Kirby et al (2008) show that as a consequence of intergenerational transmission languages “culturally evolve in such a way as to maximize their own transmissibility: over time, the languages in our experiments become easier to learn and increasingly structured.” In these experiments a subject is exposed to an alien language, made up of two elements within a finite space: meanings (consisting of a picture with three discernible elements: colour, shape and movement) paired with signals (consisting of a string of letters). Importantly, the subject is only exposed to a set amount of meanings (SEEN items), after which they are then presented with a group of meanings (some SEEN, some UNSEEN) without the corresponding signal — the goal being that they provide a response (be it the correct version or not). On completion of forming the meaning-signal pairs the experiment is repeated, except this time the new subjects are trained on the data provided by the previous generation. This continues until the experiment is finished, which in this case happened at generation ten.
A prominent idea in linguistics is that humans have an array of specialised organs geared towards the production, reception and comprehension of language. For some features, particularly the physical capacity to produce and receive multiple vocalizations, there is ample evidence for specialisation: a descended larynx (Lieberman, 2003), thoracic breathing (MacLarnon & Hewitt, 1999), and several distinct hearing organs (Hawks, in press). Given that these features are firmly in the domain of biology, it makes intuitive sense to apply the theory of natural selection to solve the problem: humans are specially adapted to the production and reception of multiple vocalizations.