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Diana Deutsch and her collaborators have done extensive study on the perceptualeffects of Shepard tones.  Among other things, she has found that, indeed, the direction of height is determined by proximity of tones.

For instance, C to C# is up, F# to E is down, B to G is down, and so on:

  

Once we get to the tritone, however, the aspect of proximity is no longer a relevant aspect.  Is the tritone interval of C to F# up or down?