Sensory perception of mechanical attributes by humans is frequently based on information generated during deformation of the assessed object with the relatively soft fingertips or the tongue. The mechanical sensitivity of a testing system, in which the machines own deformability is considerable relative to that of the specimen, depends on the deformation pattern of both machine and specimen as well as the applied force. The mechanical sensitivity of such a system is constant and force independent if both have the same compressibility. If the machine is compressible and the specimen yielding the sensitivity can be larger than unity, depending on the relative rigidity of the machine and the magnitude of the applied force. There are also situations where the mechanical sensitivity is negative which means that the resistance of the machine‐specimen array decreases while that of the tested object increases. Under most circumstances, however, compressibility of the machine increases the mechanical sensitivity of the system within the range between zero and unity, as demonstrated with experimental data of a human finger and a variety of foods.