Ask anyone what the senses are, and they are likely to list the five major senses: taste, smell, touch, hearing, and sight. However, these are not all of the senses. The most obvious omission from this list is balance/equilibrium. A special sense is one that has a specific organ devoted to it, namely the eye, ear, tongue, or nose.

Each of the senses is referred to as a sensory modality. Modality refers to the way that information is encoded, which is similar to the idea of transduction. The main sensory modalities can be described on the basis of how each is transduced. The chemical senses are taste and smell. Hearing and equilibrium are sensed by mechanoreceptors. Finally, vision involves the activation of photoreceptors.