The effect of spectral motion on the tritone paradox was investigated by pretesting subjects residing in southwestern Ontario, Canada, on the tritone task, presenting them with a continuous ascending or descending chromatic scale created using Shepard tones, and then retesting them on the tritone task. Results indicated a negative-motion aftereffect that affected the orientation of the pitch class circle. Differential effects of perceived pitch height on the lower portion of the pitch class circle and of adaptation on the upper portion of the pitch class circle were found in the pre-and postadaptation data, respectively. The implications of this dissociation are discussed. In addition, since our subjects lived relatively close to the U.S. border, the experimental pretests allowed us to examine the hypothesis that a canonical American pitch template similar to that found among "Californian" subjects (Deutsch, 1991) is propagated by linguistic influences of media such as television and radio (Ragozzine & Deutsch, 1994). A survey of our subjects indicated that overall, the majority of time engaged in listening to the radio and watching television or movies was spent with American sources. Despite this, and despite the fact that subjects had widely varying language and cultural backgrounds, a tight distribution of peak-pitch classes was found that is indicative of a "British" pitch template (Deutsch, 1991) for every subject tested.For more than 30 years, researchers have made use of specially designed complex harmonic tones in their investigations of different perceptual attributes associated with tonal relationships (Shepard, 1964). In these Shepard tones, adjacent partials are spaced at octave intervals and then filtered through a constant spectral envelope. Shepard tones are useful as stimuli in many psychoacoustic investigations because they ambiguate pitch height while maintaining the chroma of the tone being played. For example, repetitively playing the same 12 chromatic tones spanning an octave will create an illusion of a continuous ascending or descending pitch sequence, depending on whether one plays the chromatic series as ascending or descending, respectively ( Figure IA).Playing pairs ofsuch tones will create the perception of an ascending or descending interval on the basis of pitch proximity. Ifthe second tone is less than halfan octave (an interval called the "tritone") above the first, one typically perceives an ascending interval, whereas if the interval is greater than the tritone, one perceives it as descendingThe authors are grateful to 1. Visser for her assistance in running subjects, A. Cohen for providing information regarding an unpublished study, and K. Kewish, D. Deutsch, B. Repp, and an anonymous reviewer for helpful comments. This research was supported by grants to L