1. By the use of Signal Detection Theory techniques resistive load detection sensitivity was estimated in ten normal subjects during loading of the whole of inspiration and compared with loading restricted to the initial, accelerating phase of inspiratory air flow.
2. Detection sensitivity during the accelerating-flow phase of inspiration was not significantly different from that in the control conditions.
3. These results suggest that the information for detection is generated in the accelerating phase of inspiratory air flow.
4. We propose that the stimulus for resistive load detection is the ratio of the rate of change of pressure to the rate of change of flow.