In 1974, Ulf Lindblom studied how the speed of a stimulus affects absolute threshold. A WaveTek stimulator was used to measure absolute threshold of touch by "tapping" a participant's finger pad with a 2 mm diameter probe. Lindblom found that on average, there was a 27% difference in threshold level between slow and fast mechanical pulses on a participant's finger pad. The threshold for rapid pulses was 5 µm, and 80 µm for slow pulses. Lindblom's study shows that humans are more sensitive to fast stimulation than slow stimulation, at least for touch.