Response probability and response latency to threshold electrocutaneous stimuli

A comparison was made between two measures of somatosensory sensitivity, response probability, and reaction time to electrocutaneous constant current pulses of 350-microsec duration. The psychometric functions are steeper than those obtained for other sensory modalities. Similarly, the reaction-time/intensity functions are also steeper than those obtained in other modalities, i.e., larger decreases in reaction time as a function of small increases in stimulus intensity. Ss exposed to a broad stimulus range, including high intensities, yield psychometric and reaction time functions displaced into a higher intensity region than when they are exposed to a narrow low-intensity range of stimuli. The data are discussed in terms of a decision-theory model of reaction time.