Speech Planning at Turn Transitions in Dialog Is Associated With Increased Processing Load

Abstract

Speech planning is a sophisticated process. In dialog, it regularly starts in overlap with an incoming turn by a conversation partner. We show that planning spoken responses in overlap with incoming turns is associated with higher processing load than planning in silence. In a dialogic experiment, participants took turns with a confederate describing lists of objects. The confederate’s utterances (to which participants responded) were pre‐recorded and varied in whether they ended in a verb or an object noun and whether this ending was predictable or not. We found that response planning in overlap with sentence‐final verbs evokes larger task‐evoked pupillary responses, while end predictability had no effect. This finding indicates that planning in overlap leads to higher processing load for next speakers in dialog and that next speakers do not proactively modulate the time course of their response planning based on their predictions of turn endings. The turn‐taking system exerts pressure on the language processing system by pushing speakers to plan in overlap despite the ensuing increase in processing load.

Next speakers plan word forms in overlap with the incoming turn: evidence from gaze-contingent switch task performance

“…While naming latencies in the presented experiments are generally longer than average turn-transition times in conversational settings, the attested effects can be taken as informative about the processes of speech planning in conversation, where context, topic familiarity, predictable sequences of actions and the like speed up turn taking. The presented results support models of the psycholinguistics of dialogue that model response planning as taking place as early as possible (Heldner & Edlund, 2010;Levinson & Torreira, 2015), showing that early planning at least includes the stages of conceptual planning and formulation, even though processing costs in response preparation are higher in overlap with the incoming turn than during the silence between turns (Barthel & Sauppe, 2019). A recent study by Bögels and Levinson (in prep.…”

“…While a number of studies have shown that next speakers initiate planning in overlap, they did not investigate which steps of response preparation are run through while the current turn is still coming in and potentially interfering with simultaneously running planning processes. Planning in overlap comes at the cost of increased processing load (Barthel & Sauppe, 2019), which might cause next speakers to postpone certain processing stages until the end of the incoming turn in order to avoid high peaks in processing load.…”

“…This pattern of results shows that high verbal working memory load interferes with phonological production planning. Taking together these findings, postponing (at least) phonological planning until the end of the incoming turn could therefore be an efficient strategy that might be applied by next speakers to keep the increase in processing costs that come with planning in overlap at a moderate level (Barthel & Sauppe, 2019). On the other hand, late phonological planning might lead to long gaps between turns that might be undesired because long delays give rise to inferences on the turn's meaning (Bögels, Kendrick, & Levinson, 2015;Clayman, 2002;Pomeranz & Heritage, 2012) and might commonly be avoided for that reason.…”

Neural correlates of turn-taking in the wild: Response planning starts early in free interviews

“…On the other hand, a recent study on turn-taking (Barthel & Sauppe, 2019) showed that production planning led to higher processing load (as measured by pupillary responses) when it started in overlap with the current turn than when it could only start when that turn had finished.…”

“…Such overlap may be problematic given that language production (planning) and comprehension rely on largely the same cognitive and neuronal architecture (e.g., Segaert, Menenti, Weber, Petersson, & Hagoort, 2012) and both processes have been shown to require central attention (e.g., Kubose et al, 2006;Shitova, Roelofs, Coughler, & Schriefers, 2017). Indeed, dual tasking with two linguistic tasks leads to more interference than when one of the tasks is non-linguistic (Fairs, Bögels, & Meyer, 2018), and production planning in turn-taking happening in overlap with concurrent speech input leads to increased processing load as compared to planning 'in the clear', as measured by pupillary responses (Barthel & Sauppe, 2019). Thus, one might predict that interlocutors attempt to keep the amount of overlap between comprehension and production minimal, that is, start planning as late as possible.…”