ABSTRACT
The taction sense relates to contact and touch at the skin. One speaks of a tactile sensation when the stimulus solely acts at the skin; while a haptic sensation exists when information flows at the same time from sensors in muscles, tendons, and join. Objects at skin temperature appear as neutral or indifferent, at "physiological zero." Olfactory information is seldom used by engineers, because few research results are available, because people react quite differently to olfactory stimuli, because smells can be easily masked, and because olfactory stimuli are difficult to arrange. Pain does not lend itself to engineering applications, because one is ethically bound not to cause pain, but also because the sensation of pain follows any damage already done too slowly to prevent more damage. Motion time follows reaction time. Movements may be simple, such as lifting a finger in response to a stimulus, or complex, such as swerving a car to avoid a collision.
