OBJECTIVE: This study aimed to develop an experimental paradigm, using healthy controls, to measure change in tactile sensitivity and response bias for subsequent testing of patients with medically unexplained symptoms (MUS). METHODS: Participants judged whether or not they detected a weak tactile pulse (presented in 50% of trials). Performance in two conditions (tactile pulses presented with or without a concomitant light) was compared using signal detection analysis to assess whether a task-irrelevant light can invoke the sensation of touch, even in its absence. RESULTS: The results showed that the presence of a concurrent light significantly improved participants' detection of the tactile stimulus by 13.7% [t(18)=4.24, P