Interference in picture naming occurs from representing a partner's preparations to speak (Gambi, van de Cavey, & Pickering, 2015). We tested the origins of this interference using a simple non-communicative joint naming task based on Gambi et al. (2015), where response latencies indexed interference from partner task and partner speech content, and eye fixations to partner objects indexed overt attention. Experiment 1 contrasted a partnerpresent condition with a control partner-absent condition to establish the role of the partner in eliciting interference. For latencies, we observed interference from the partner's task and speech content, with interference increasing due to partner task in the partner-present condition. Eye-tracking measures showed that interference in naming was not due to overt attention to partner stimuli but to broad expectations about likely utterances. Experiment 2 examined whether an equivalent non-verbal task also elicited interference, as predicted from a language as joint action framework. We replicated the finding of interference due to partner task and again found no relationship between overt attention and interference. These results support Gambi et al. (2015). Individuals co-represent a partner's task while speaking, and doing so does not require overt attention to partner stimuli.

When attempting to maintain conversations in noisy communicative settings, talkers typically modify their speech to make themselves understood by the listener. In this study, we investigated the impact of background interference type and talker age on speech adaptations, vocal effort and communicative success. We measured speech acoustics (articulation rate, mid-frequency energy, fundamental frequency), vocal effort (correlation between mid-frequency energy and fundamental frequency) and task completion time in 114 participants aged 8–80 years carrying out an interactive problem-solving task in good and noisy listening conditions (quiet, non-speech noise, background speech). We found greater changes in fundamental frequency and mid-frequency energy in non-speech noise than in background speech and similar reductions in articulation rate in both. However, older participants (50+ years) increased vocal effort in both background interference types, whereas younger children (less than 13 years) increased vocal effort only in background speech. The presence of background interference did not lead to longer task completion times. These results suggest that when the background interference involves a higher cognitive load, as in the case of other speech of other talkers, children and older talkers need to exert more vocal effort to ensure successful communication. We discuss these findings within the communication effort framework. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part II)’.

The impact of energetic (EM) and informational masking (IM) on speech communication is typically evaluated using perception tests that do not involve actual communication. Here, ratings of effort, concentration and degree of interference were obtained for 51 young, middle-aged and older adults after they had completed communicative tasks (Diapix) with another participant in conditions in which no noise, speech-shaped noise, or three voices were heard in the background. They also completed background sensory and cognitive tests and a quality of hearing questionnaire. The EM condition was perceived as less effortful, requiring less concentration and easier to ignore than those involving IM. Effects were generally greater for talkers taking the lead in the interaction. Even though the two older groups were more affected by IM than young adults in a speech in noise perception test, age did not impact on ratings of effort and ability to ignore the noise in the diapix communicative task. Only for concentration ratings, did the Older Adult group give similar ratings in quiet as when EM was present. Together, these results suggest that evaluations that purely assess receptive speech in older adults do not fully represent the impact of sources of interference on speech communication.

Disfluencies are a pervasive feature of speech communication. Their function in communication is still widely discussed with some proposing that their usage might aid understanding. Accordingly, talkers may produce more disfluencies when conversing in adverse communicative situations, e.g. in background noise. Moreover, increasing age may have an effect on disfluency use as older adults report particular difficulties when communicating in adverse conditions. In this study, we elicited spontaneous speech via a problem-solving task from four different age groups (19-76 years old) to investigate the effect of energetic and informational maskers on the use of filled pauses (FPs), and its interaction with age. Measures of disfluency rates, effort ratings, and communication efficiency were obtained. Results show that, against our predictions, FP usage may decrease in adverse conditions. Moreover, age does not play a great role in adults with normal hearing. The results indicate that individuals differ greatly in their disfluency adaptations, utilising different strategies to overcome challenging communicative situations