Exposure-based Perceptual Learning in Discrimination of Sythetic Timbres

Exposure to a stimulus has the potential to bring about perceptual learning that streamlines cognitive processing in subsequent exposures, leading to more accurate discriminations of related stimuli (Fahle, 2005). The present study explored whether learning through experience with perceptual stimuli could be extended to timbral discrimination in the auditory domain, and, if so, whether learning required guidance beyond simple exposure. A timbre continuum blending the timbres of an oboe and a trumpet was constructed, producing 48 novel timbres to which participants had no previous exposure. Participants’ sensitivity (d’) to these timbres were measured before and after exposure training that was inclusive or exclusive of accuracy-based training feedback. Although neither training method improved discrimination performance with sub-threshold timbral variation of tone pairs (Experiment 1), feedback-based training significantly increased discrimination of tone pairs with supra-threshold timbral variation (Experiment 2). Experiment 3 expanded on this finding by testing the generalizability of the discrimination learning; whereas some learning-based performance improvements can be transferred to related tasks (e.g., Ragert, Schmidt, Altenmüller, & Dinse, 2004), others are highly specific to the training that led to them (Fahle & Edelman, 1993). Participants in Experiment 3 underwent exposure-based training to recognize the timbre of one set of tones and were later asked to discriminate a different set of tones composed in the trained timbre. Feedback-based training led not only to better discrimination of the trained tones, but also increased d’ for untrained tones played in the trained timbre.