Abstract
This study examined longitudinal changes in second language (L2) interlocutors’ mutual comprehensibility ratings
(perceived ease of understanding speech), targeting comprehensibility as a dynamic, time-varying, interaction-centered construct.
In a repeated-measures, within-participants design, 20 pairs of L2 English university students from different language backgrounds
engaged in three collaborative and interactive tasks over 17 minutes, rating their partner’s comprehensibility at 2–3 minute
intervals using 100-millimeter scales (seven ratings per interlocutor). Mutual comprehensibility ratings followed a U-shaped
function over time, with comprehensibility (initially perceived to be high) being affected by task complexity but then reaching
high levels by the end of the interaction. The interlocutors’ ratings also became more similar to each other early on and remained
aligned throughout the interaction. These findings demonstrate the dynamic nature of comprehensibility between L2 interlocutors
and suggest the need for L2 comprehensibility research to account for the effects of interaction, task, and time on
comprehensibility measurements.