Complexity, frequency, and acceptability

It is sometimes argued that (certain types of) lexical frequency and constructional frequency determine how easy sentences are to process and hence, how acceptable speakers find them. Others have argued that grammatical principles interact with and often override such effects. Here, we present the results from a survey on Danish with more than 200 participants. We asked people to provide acceptability ratings of a number of sentences with varying levels of complexity, with and without extraction, including complement clauses, relative clauses, parasitic gaps, and ungrammatical sentences. We predicted structural complexity and acceptability to be negatively correlated (the more complex, the less acceptable). The results show that construction frequency and acceptability are correlated, but that zero and near-zero frequencies do not predict acceptability. However, there is indeed an even stronger inverse correlation between acceptability and structural complexity, defined as a function of independently motivated factors of syntactic structure and processing, including embedding, adjunction, extraction, and distance between filler and gap. Lexical frequency also affects acceptability, but the effects are small, and, crucially, there is no evidence in our data that ungrammatical sentences are affected by such frequency effects. Furthermore, the acceptability patterns seem to be fairly stable across participants. The results show a pattern that is consistent with an approach based on grammatical principles and processing constraints, rather than based on stochastic principles alone.