Different Patterns of Human Discrimination Learning for Two Interaural Cues to Sound-Source Location

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 98; no. 21; pp. 12307 - 12312
• Main Authors: Wright, Beverly A., Fitzgerald, Matthew B.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.10.2001; National Acad Sciences; The National Academy of Sciences
• Series: From the Cover
• Subjects: Acoustic Stimulation; Adult; Aural learning; Cues; Discrimination learning; Discrimination Learning - physiology; Discriminative listening; Ears & hearing; Female; Hearing tests; Humans; Learning; Learning rate; Male; Psychology; Retention (Psychology); Sensory discrimination; Social Sciences; Sound; Training; Z score
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.211220498

Two of the primary cues used to localize the sources of sounds are interaural level differences (ILDs) and interaural time differences (ITDs). We conducted two experiments to explore how practice affects the human discrimination of values of ILDs and ongoing ITDs presented over headphones. We measured discrimination thresholds of 13 to 32 naive listeners in a variety of conditions during a pretest and again, 2 weeks later, during a posttest. Between those two tests, we trained a subset of listeners 1 h per day for 9 days on a single ILD or ITD condition. Listeners improved on both ILD and ITD discrimination. Improvement was initially rapid for both cue types and appeared to generalize broadly across conditions, indicating conceptual or procedural learning. A subsequent slower-improvement stage, which occurred solely for the ILD cue, only affected conditions with the trained stimulus frequency, suggesting that stimulus processing had fundamentally changed. These different learning patterns indicate that practice affects the attention to, or low-level encoding of, ILDs and ITDs at sites at which the two cue types are processed separately. Thus, these data reveal differences in the effect of practice on ILD and ITD discrimination, and provide insight into the encoding of these two cues to sound-source location in humans.