Listeners use perceptual learning to rapidly adapt to manipulated speech input. Examination of this learning process can reveal the pathways used during speech perception. By assessing generalization of perceptually learned categorization boundaries, others have used perceptual learning to help determine whether abstract units are necessary for listeners and models of speech perception. Here we extend this approach to address the inverse issue of specificity. In these experiments we have sought to discover the levels of specificity for which listeners can learn variation in phonetic contrasts. We find that (1) listeners are able to learn multiple voicing boundaries for different pairs of phonemic contrasts relying on the same feature contrast. (2) Listeners generalize voicing boundaries to untrained continua with the same onset as the trained continua, but generalization to continua with different onsets depends on previous experience with other continua sharing this different onset. (3) Listeners can learn different voicing boundaries for continua with the same CV onset, which suggests that boundaries are lexically-specific. (4) Listeners can learn different voicing boundaries for multiple talkers even when they are not given instructions about talkers and their task does not require talker identification. (5) Listeners retain talker-specific boundaries after training on a new boundary for a second talker, but generalize boundaries across talkers when they have no previous experience with a talker. These results were obtained using a new paradigm for unsupervised perceptual learning in speech. They suggest that models of speech perception must be highly flexible in order to accommodate both specificity and generalization of perceptually learned categorization boundaries.

This thesis presents four experimental studies, carried out at the Phonetic laboratory, Stockholm University, on infants’ ability to establish auditory-visual sound-meaning associations as a precursor of early word acquisition. Study I reports on the effect of linguistic variance on infants’ ability (3- to 20-months) to establish sound-meaning associations. The target-words embedded in phrases, based on an artificial language, were presented along with visually displayed puppets. Study II investigates the role of attribute type on infants’ ability (3- to 6-months) to establish sound-meaning associations. Two-word phrases, based on the same artificial language as in Study I, were presented along with visually displayed geometrical objects. The words implicitly referred to the color and shape of the objects. Study III examines infants’ ability (12- to 16-months) to predict phonetic information. The subjects were tested on their ability to associate Swedish whole words and disrupted words to familiar objects. Study IV investigates infants’ ability (6- to 8-months) to detect concurrence and synchrony in speech and non-speech. The infants were exposed to Swedish speech sounds presented with corresponding articulatory events, the sound of hand-clapping presented with synchronized hand-clapping movements, and the sound of hand-clapping presented with synchronized articulatory events. The results picture the subject as sensitive to distributional properties of auditory and visual information (Study I and II) but still unable to predict phonetic information, in the beginning of the second year of life (Study III). The infants’ conceptual behavior is outlined as a general-purpose perceptual process influenced by perceptual salience (Study IV). These results are related to a working hypothesis based on the Ecological theory of language acquisition (Lacerda &amp; Sundberg, 2006), and Lindblom (Lindblom, 1990; Lindblom &amp; Lacerda, 2006). / <p>För att köpa boken skicka en beställning till exp@ling.su.se/ To order the book send an e-mail to exp@ling.su.se</p>