Deutsch, D., Kuyper, W.L., Fisher, Y. (1987). The tritone paradox: Its presence and form of distribution in a general population. Music Percept. 5, 79-92
The tritone paradox occcurs when an ordered pair of tones is presented, with each tone consisting of a set of octave-related components, and the pitch classes of the tones separated by a half-octave. Such a pattern is heard as ascending in one key, but as descending in a different key. Further, the pattern in any one key is heard as ascending by some listeners but as descending by others. It was here found that this phenomenon occurs to a highly significant extent in a general population, and that it is distributed within the population in an orderly fashion. The findings also reveal a surprising ability within the general population to utilize absolute pitch.