Effects of linguistic redundancy and coded voice warnings on system response time

Similar system response times have been reported for keyword and semantic context warning messages based on the premise that the linguistic redundancy of semantic context warnings require less attention than the shorter keyword warnings. The present study was conducted to learn whether an initial word of warning could be used for alerting purposes without increasing system response time and whether or not differences exist between the keyword and semantic conditions. Fifteen subjects were given a flying task using an IBM PC Flight Simulator package and responded to synthesised speech warnings under conditions of cockpit conversation, simulated noise and various flying duties. The keyword-only condition provided a statistically significant lower SRT than all other conditions but, with larger movement/reaction time, appeared to have placed the greatest cognitive demand on subjects. Recommendations are made on the implications regarding the use of the keyword-only format.