Cross-modal warning effect's on reflexive and voluntary reactions

Previous research has shown that warning signals can speed the onset of the startle-blink reflex. To relate this phenomenon to warning effects on volu ntary reaction time (RT), the latencies of both reflexive and voluntary res ponses were measured for nine factorial combinations of warning and reflexo genic stimulus modalities. Previous failures to use factorial manipulations of warning (S-1) and reaction (S-2) stimulus modalities have led to confli cting results in both the reflex and RT literatures. Using psychophysically matched warning signals, we found a facilitation of reflex latency that wa s nonspecific with regard to S-1 and S-2 modality. Furthermore, there was n o support for the widely held assumption that visual stimuli are inherently less alerting than auditory and cutaneous stimuli. A between-group compari son showed that simultaneous voluntary reactions do not distort the reflex facilitation effect. These results support the validity of reflex facilitat ion as a simple model system for studying warning effects on sensorimotor r eactions.