Auto-Wiper Behavior

Another silly little question - with rain-sensor wipers, I know I can turn on and off the sensor. If it's off, the little toggle switch on top of the wiper lever changes the intermittent delay interval. But does that delay switch do anything when the rain sensor is turned on? What, exactly? I find that the rain sensor generally works OK, but occasionally is slower to respond to rain than I would like. Twiddling the little delay switch DOES seem to wake the wipers up nicely at least at first. But no particular position of the delay switch seems to keep the auto wipers quite responsive enough. Any expert opinions out there?