Impact of Presentation Order on Pitch Ranking Sensitivity in Cochlear Implant Users and Normal-Hearing Listeners and...

Accurate pitch perception in cochlear implants (CIs) remains challenging, making psychophysical measures susceptible to procedural biases. In unilateral pitch ranking, subjects judge which of two successive stimuli is higher in pitch, typically yielding electrode order roughly consistent with tonotopy. In our study with 10 MED-EL CI users, each of the 12 electrodes was compared with its three next neighbors. Pitch ranking was influenced by the presentation order of the electrode pairs. To investigate this effect, we tested 9 normal-hearing (NH) listeners using bandpass-filtered noise (6 dB/oct slopes) to approximate current spread during CI stimulation. Comparable performances across CI and NH in all three spacing conditions indicated similar pitch perception difficulty. On average, both groups discriminated 8 of 12 channels based solely on pitch (discriminability via d'), suggesting that 6 dB/oct slopes approximate mean monopolar current spread at the group level. Pitch rankings of adjacent channels exhibited biases. A repeated-measures ANOVA revealed a significant interaction between presentation order and stimulation site in both groups (CI: p = .003; NH: p < .001): pairs below the stimulus range midpoint were more often reported as descending, whereas pairs above the middle were more often reported as ascending. This asymmetric bias may reflect a context-dependent decision process in which subjects compare the second stimulus to a weighted average of the first and previously presented stimuli. Presentation-order effects were mitigated by testing stimulus pairs in isolation, at the expense of reduced randomization. Our findings highlight the importance of controlling biases to ensure reliable psychophysical measures.