Effects of delay on perceived quality, behavior and oscillatory brain activity in dyadic telephone conversations

End-to-end delay is an important factor when studying the quality of modern packet-based telephone conversations. Other than most degradations, delay cannot be assessed by listen-only tests and mainly impacts the structure and interactivity of the conversation. Because of this, the modeling of the perceived quality of conversation under delay is dependent on various instrumental as well as human-related influencing factors. Physiological methods in particular might provide additional insights into how human participants are affected by such quality degradations during natural conversations. In the present experiment, a novel dual-electroencephalo-graphy (dual-EEG) method was employed to investigate the effects of delay on 10 pairs of participants engaging in dyadic conversations. In each test session, neurophysiological activity was registered simultaneously in both interlocutors, who interacted in accordance with short conversation test scenarios (SCIs) through an audio network. Meanwhile, delays of different magnitudes (0, 800, 1600 ms) were inserted into the network, which was expected to interfere with the conversation and cause changes in the participants' internal processing and state. Analysis of subjective and behavioral measures shows a decrease in perceived quality and of conversational interactivity with higher levels of delay. Moreover, an initial intra-brain analysis of the recorded dual-EEG data (N = 18) revealed significant modulations in beta and gamma frequency bands by varying delay level. This suggests that attentional load increased with high delay, probably due to less amounts of single talk and focusing more on the adaptation of the own turn-taking behavior.