Postulated by the Korean-American Doctor M.H. Cho in the 1970’s. He observed that a temperature change in the body, leads to a temperature change in the ear. A temperature change in the ear, leads to a temperature change in the body.

Delta reflex theory posits that cold or heat stimulation on parts of the body, raises the temperature in the corresponding parts of the ear, from 1.0°C to 5.5°C.

The theory he proposed, posits a relationship between parts of the body, and the regions of the ear. This reflex may be influenced in part by the vagus nerve.