The effects of message length, L2 proficiency and cognitive workload on performance accuracy and speech production in a simulated pilot navigation task

The goal of the present study was to investigate the influence of L2 proficiency in controller-pilot communications under conditions of varying cognitive workload. The study therefore examined the effects of L2 proficiency and cognitive workload on performance accuracy and speech production in a simulated pilot navigation task. Three groups of 20 participants (one native-English speaking and two native-Mandarin speaking of relatively high and low levels of proficiency in English) took part in the experiment. Participants listened to, repeated and responded to "controller" messages (in English) of varying lengths in two conditions: clear and workload. In the workload condition, participants performed a concurrent arithmetic task while repeating the controller message.; The dependent variables were divided into two sets: performance accuracy (message repetition and navigation accuracy), and speech production (accentedness, comprehensibility, fluency and confidence, as perceived by 10 native-English speaking raters). Based on the results of the present study, it is recommended that air traffic controllers limit their messages to a length of 2 commands when communicating with L1 pilots under high workload conditions. When communicating with L2 pilots of low or intermediate L2 proficiency, it is recommended that controllers limit the length of their messages to 1 command under high cognitive workload conditions. A significant detriment to speech production due to increased message length was observed for the L2 groups for all speech production measures. A significant detriment to speech production due to increased cognitive workload was observed for the Low L2-proficiency group for the perceived fluency measure.