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Greater informational masking is observed when the target and masker speech are more perceptually similar. Fundamental frequency (f0) contour, or the dynamic movement of f0, is thought to provide cues for segregating target speech presented in a speech masker. Most of the data demonstrating this effect have been collected using digitally modified stimuli. Less work has been done exploring the role of f0 contour for speech-in-speech recognition when all of the stimuli have been produced naturally. The goal of this project was to explore the importance of target and masker f0 contour similarity by manipulating the speaking style of talkers producing the target and masker speech streams. Sentence recognition thresholds were evaluated for target and masker speech that was produced with either flat, normal, or exaggerated speaking styles; performance was also measured in speech spectrum shaped noise and for conditions in which the stimuli were processed through an ideal-binary mask. Results confirmed that similarities in f0 contour depth elevated speech-in-speech recognition thresholds; however, when the target and masker had similar contour depths, targets with normal f0 contours were more resistant to masking than targets with flat or exaggerated contours. Differences in energetic masking across stimuli cannot account for these results.