1. Second Language Acquisition and Social Coordination Seán Roberts LEC, University of Edinburgh

2. Second Language Acquisition Child Acquisition Rapid Effortless Implicit Universal Adult Acquisition Slow Difficult Explicit Rarely native competence Why?

3. Adult SLA Why are adults worse at SLA? Constraints on Memory Paradis (2004), Ullman (2001) Hagen 2008: Memory changes to fit social structure (interactions between groups) BUT: Language Changes to fit social structure (social structure of learners) Christiansen & Chater, 2008, Lupyan & Dale, 2010

4. Procedural and Declarative Memory Procedural Memory for Grammar Declarative Memory for Lexicon Paradis (2004), Ullman (2001), DiGiulio (2004) The ability to incorporate knowledge into procedural memory atrophies in adults So they compensate by using declarative memory Procedural Declarative Age

5. Child vs. Adult Acquisition Linguistic capacities provide insights into the evolutionary pressures acting on our ancestors Hagen (2008): Atrophy of procedural memory suggests that language acquisition was useful for children,but not for adults Adult SLA was not selected for propagation. Adult SLA erodes due to drift

6. Human nature Linguistic capacities provide insights into the societies of our ancestors Adults are not good at SLA: Hobbesian competitiveness Children are good at bilingualism: Rousseauian egalitarianism

7. Procedural Memory Declines in adulthood Linguistic diversity suggests isolation Not much opportunity for trade Conquering another group is easier and more rewarding than learning their language SLA and Social Structure Decline of Procedural Memory starts late in the life of early humans. Gareth Roberts (2010): Linguistic diversity may stem from competition Nettle and Romanie (2000): Social investment when trade is redundant Hirchfield (2008): Exogamous marriage Not much warfare if there is little contact

8. Alternative Hypothesis Languages change much faster than genes Languages adapt to the cognitive niche of its learners Christiansen & Chater (2008) HYP If children (the learners) are still developing declarative memory, then language will adapt to procedural memory. So language is not adapted for adults using declarative memory

9. Languages adapt to Social Structure Lupyan & Dale (2010): Esoteric populations: Few speakers, small dispersal, little contact with other communities: Language is Morphologically complex Exoteric populations Many speakers, widely dispersed, many second language speakers: Language uses Lexical strategies

11. Log Population English First Language: 300-400 million Second Language: 200 - 14,000 million (Ethnologue, SIL International) Lupyan & Dale(2010) Complexity Score

12. Summary If there are many child learners (procedural memory users) the language will adapt to use morphological strategies of distinction which are easier to learn using procedural memory If there are many adult learners (declarative memory users) the language will adapt to use lexical strategies of distinction which are easier to learn using declarative memory

13. Conclusion Hagen: Inferring social structure from the structure of memory: Memory adapts to small, isolated populations. Alternative: Inferring social structure from language structure: Language adapts to learners Inferences about past social structures may not be possible because of rate of change in languages