Pitch Increases from Left to Right on Piano keyboards. When pianists press keys on a keyboard to hear two successive octave-ambiguous tones spanning a tritone (half-octave interval), they tend to report hearing the tritone go in the direction consistent with their key presses (Repp & Knoblich, 2009). This finding has been interpreted as an effect of action on perceptual judgment. Using a modified design, the present study separated the effect of the action itself from that of the visual stimuli that prompt the action. Twelve expert pianists reported their perception of octave-ambiguous three-note melodies ending with tritones in two conditions: In the active condition, they saw a notated melody and played it on a keyboard to hear it, while in the passive condition they viewed the notation while the melody was played to them. Participants tended to report hearing the tritone as it appeared in the notation, but action had no additional effect. We discuss whether the "action direction effect" described by Repp and Knoblich may have been caused by the visual action prompts, not by the action itself.
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