A decision as to whether two line segments are colinear, as on a vernier scale (--/-- vs --/--), can be made with high sensitivity by the human visual system. Just-noticeable vernier displacement is much smaller than the separation required to resolve two parallel lines, i.e., to perceive them as two lines rather than one. Vernier acuity is thus also called "hyperacuity." Similar effects have been discovered in bat echolocation, for discrimination of a range-jittered point target from a nonjittered target, in the jamming avoidance response (JAR) of electric fish, and in differential pitch sensitivity experiments with human subjects. Are jitter sensitivity in echolocation, JAR in electroreception, differential pitch sensitivity in audition, and vernier acuity in vision based on the same general principle? The results in this article indicate that such phenomena are indeed similar from the viewpoint of detection theory, and that experimental performance can be used to behaviorally estimate auditory parameters such as bandwidth, beamwidth, and temporal resolution, as well as to test different signal processing models without resort to masking. Applications of the hyperacuity effect to radar, sonar, and medical ultrasound are suggested.