Comparison of voice F₀ responses to pitch-shift onset and offset conditions (L)

In order to maintain a steady voice fundamental frequency (F₀), it is assumed that people compare their auditory feedback pitch with an internal (memory) or external (acoustic) referent. In the present study we examined whether the internal referent is fixed or variable by comparing voice F₀ responses to incorrect auditory feedback in two timing conditions. In one condition, the incorrect pitch was introduced during vocalization (ON condition). In the second, the incorrect auditory feedback pitch was presented before vocal onset and then removed during vocalization (OFF condition). These conditions were examined with pitch-shift stimuli of ±25, 100, and 200 cents. There were no differences in response latency or magnitude between the two timing conditions, indicating that for a sustained-pitch vocalization task, the internal referent is not fixed. Several alternative types of referencing are discussed, which include use of a pitch relative to that which existed at the onset of vocalization (a sample and hold strategy) and pitch velocity referencing.