Rethinking the Missing Fundamental: Instability and Variability in Pitch Perception Driven by Contextual Effects and Expectation-Based Priming

The Missing Fundamental (MF) phenomenon refers to the perception of a fundamental frequency (F₀) even when the F₀ and parts of the harmonic series are removed from a complex tone. However, in an incidental experiment, the author observed that the perceived pitch of MF stimuli is not always stable. This study systematically investigates this instability and demonstrates that, in the absence of explicit expectations, listeners tend to perceive the MF pitch as falling between two reference sine tones. When listeners are primed with an expected pitch pattern, they are able to intentionally shift their perception of the MF pitch to match that expectation. Moreover, this modulation appears to be driven not by physical acoustic features, but by mental imagery and cognitive influence. These findings challenge classical models of pitch perception, suggesting that pitch may be a top-down psychological representation rather than a purely bottom-up neural response.