The effects of utterance timing and stimulation of left prefrontal cortex on the production of referential expressions

Abstract

We examined the relationship between the timing of utterance initiation and the choice of referring expressions, e.g., pronouns (it), zeros (…and went down), or descriptive NPs (the pink pentagon). We examined language production in healthy adults, and used anodal transcranial direct current stimulation (tDCS) to test the involvement of the left prefrontal cortex (PFC) on the timing of utterance production and the selection of reference forms in a discourse context. Twenty-two subjects (11 anodal, 11 sham) described fast-paced actions, e.g. The gray oval flashes, then it moves right 2 blocks. We only examined trials in contexts that supported pronoun/zero use. For sham participants, pronouns/zeros increased on trials with longer latencies to initiate the target utterance, and trials where the previous trial was short. We argue that both of these conditions enabled greater message pre-planning and greater discourse connectedness: The strongest predictor of pronoun/zero usage was the presence of a connector word like and or then, which was also tended to occur on trials with longer latencies. For the anodal participants, the latency effect disappeared. PFC stimulation appeared to enable participants to produce utterances with greater discourse connectedness, even while planning incrementally.

Thematic role predictability and planning affect word duration

“…If so, the given status of the goal characters may be stronger than the given status of source characters, leading speakers to choose acoustically reduced expressions more often for goals. To our knowledge, no existing theories of information status propose that attention to the discourse context can vary, but this idea is consistent with other recent work from our lab (Arnold & Nozari, 2017;Zerkle & Arnold, in press). …”

“…Unlike Experiment 1, we found that connective use did predict duration, in that the presence of a connective led to longer durations. This effect is somewhat surprising, in that other studies have found that connectives co-occur with the choice of lexically reduced expressions like pronouns (Arnold & Griffin, 2007;Arnold & Nozari, 2017). In the current task, the connective may have been used as a mechanism for gaining additional time to prepare the utterance.…”

“…Further support comes from evidence people tend to produce pronouns (instead of names) more often in sentences that contain an explicit connective, like and or then (Arnold & Griffin, 2007;Arnold & Nozari, 2017). The presence of connective words reflects a stronger conceptual connection between the events being described in two sentences, and a greater ability or inclination for the speaker to treat the utterance as a part of the prior discourse context.…”

“…This question comes in two parts: First, we predict that planning measures affect duration, because it is likely that both acoustic duration and planning time (latency to begin speaking) are tightly related. We also coded responses for the presence of a connective word (e.g., and or then), which has been known to correlate with planning and discourse cohesiveness (Arnold & Griffin, 2007;Arnold & Nozari, 2017). Second, we ask whether thematic role affects latency itself, because predictability might also be related to the time needed for a speaker to plan their utterance.…”

Investigating the origin of nonfluency in aphasia: A path modeling approach to neuropsychology

“…There is both behavioral and neural evidence that resolving such competition requires executive control (Shao, Meyer, & Roelofs, 2013; Shao, Roelofs, & Meyer, 2012; Schnur et al, 2009). At the sentence level too, accuracy and timing of processing have been shown to depend on executive control abilities and their neural correlates, especially the left lateral prefrontal cortex, in both sentence comprehension (Nozari, Mirman, & Thompson-Schill, 2016; Nozari, Trueswell, & Thompson-Schill, 2016) and sentence production (Arnold & Nozari, 2017; Nozari, Arnold, & Thompson-Schill, 2014; see Nozari & Thompson-Schill, 2015 for a review).…”