| Speech is the tool humans use to communicate that sets us apart from any other species. It is a complex interplay between the motor speech system of the speaker and the auditory system of the listener. Self-monitoring uses what one hears to help monitor what one says by way of an automatic feedback loop. We tested the theory that humans are selectively adaptive to acoustic stimuli that contain speech-like frequencies. In Study One, we measured speech output changes given speech versus noise masks during a naming task. Results showed that noise containing speech-similar frequencies (broadband, 0.0--20 kHz; bandpassed, 0.05--4.5 kHz; high-notched, 8.0--11.5 kHz removed) elicited significant changes in the acoustic features of the speech output, while noise with speech-similar frequencies removed (low-notched, 0.5--4.5 kHz removed) did not. In Study Two, we measured duration matching accuracy, and speech output changes given speech and noise masks during a novel duration matching task. Participants matched /a/, /f/, and noise at 300 ms, 550 ms, and 800 ms lengths in quiet, speech (/a/, /i/), broadband noise, and /f/-frequency shaped noise masks. Findings showed that it was more difficult to duration match /a/ given a speech versus a noise mask. In addition, there were different error patterns between speech and noise; speech targets were overshot with error greatest at 550 ms, while noise targets were undershot with error increasing as target length increased. Collectively, results support the theory that self-monitoring in humans is selectively affected by frequencies within the speech range and that a specialized module exists for processing speech information. |
