No scope for planning: latent mixture modelling of sentence onsets

Whether or not pre-planning a sentence involves syntax hinges, partially, on the observation that, when a sentence starts with a conjoined NP, the speech onset is delayed compared to matched sentences starting in simple NPs. An alternative view is that planning beyond the subject NP is not obligated by the linguistic encoder. We contrasted these two views directly in a series of Bayesian models. Results showed that the delay for conjoined NPs happens sporadically rather systematically. We suggest that the frequently replicated slowdown for conjoined NPs might be better explained by non-syntactic processing demands.