While endorsing Evans & Levinson's (E&L's) call for rigorous documentation of variation, we defend the idea of Universal Grammar as a toolkit of language acquisition mechanisms. The authors exaggerate diversity by ignoring the space of conceivable but nonexistent languages, trivializing major design universals, conflating quantitative with qualitative variation, and assuming that the utility of a linguistic feature suffices to explain how children acquire it.

· Introduction: The Nature of Probability Theory· The Sample Space· Elements of Combinatorial Analysis· Fluctuations in Coin Tossing and Random Walks· Combination of Events· Conditional Probability· Stochastic Independence· The Binomial and Poisson Distributions· The Normal Approximation to the Binomial Distribution· Unlimited Sequences of Bernoulli Trials· Random Variables· Expectation· Laws of Large Numbers· Integral Valued Variables· Generating Functions· Compound Distributions· Branching Processes· Recurrent Events· Renewal Theory· Random Walk and Ruin Problems· Markov Chains· Algebraic Treatment of Finite Markov Chains· The Simplest Time-Dependent (...) Stochastic Processes. (shrink)

Languages are transmitted from person to person and generation to generation via a process of iterated learning: people learn a language from other people who once learned that language themselves. We analyze the consequences of iterated learning for learning algorithms based on the principles of Bayesian inference, assuming that learners compute a posterior distribution over languages by combining a prior (representing their inductive biases) with the evidence provided by linguistic data. We show that when learners sample languages from this posterior (...) distribution, iterated learning converges to a distribution over languages that is determined entirely by the prior. Under these conditions, iterated learning is a form of Gibbs sampling, a widely-used Markov chain Monte Carlo algorithm. The consequences of iterated learning are more complicated when learners choose the language with maximum posterior probability, being affected by both the prior of the learners and the amount of information transmitted between generations. We show that in this case, iterated learning corresponds to another statistical inference algorithm, a variant of the expectation-maximization (EM) algorithm. These results clarify the role of iterated learning in explanations of linguistic universals and provide a formal connection between constraints on language acquisition and the languages that come to be spoken, suggesting that information transmitted via iterated learning will ultimately come to mirror the minds of the learners. (shrink)