Short title: Unattended learning of speech components Unattended exposure to components of speech sounds yields same benefits as explicit auditory training

Unattended learning of speech components 1 ! Short title: Unattended learning of speech components Unattended exposure to components of speech sounds yields same benefits as explicit auditory training Unattended learning of speech components 2 ! Abstract Learning a second language as an adult is particularly effortful when new phonetic representations must be formed. Therefore the processes that allow learning of speech sounds are of great theoretical and practical interest. Here we examined whether perception of single formant transitions, that is, sound components critical in speech perception, can be enhanced through an implicit task-irrelevant learning procedure that has been shown to produce visual perceptual learning. The single-formant sounds were paired at sub-threshold levels with the attended targets in an auditory identification task. Results showed that task-irrelevant learning occurred for the unattended stimuli. Surprisingly, the magnitude of this learning effect was similar to that following explicit training on auditory formant transition detection using discriminable stimuli in an adaptive procedure, whereas explicit training on the subthreshold stimuli produced no learning. These results suggest that in adults learning of speech parts can occur at least partially through implicit mechanisms. Unattended learning of speech components 3 ! Unattended exposure to components of speech sounds yields same benefits as explicit auditory training Languages differ in their phonetic repertoire, that is, in the set of speech sounds that are used to form words and thus to convey distinctions in meaning. Infants learn the speech sounds of their linguistic environment in their first year of life by attending to sound differences that are related to meaning differences and ignoring inconsequential sound differences (Jusczyk, 1997). This results in more efficient processing of speech sounds used in their language and less efficient processing of other sounds (Kuhl et al., 2008). Language acquisition, in general, and phonetic learning, in particular, appear to rely heavily on implicit learning mechanisms that extract statistical regularities organized at many different levels For example, humans' sensitivity to the distributional frequencies of the acoustic input affects word segmentation and phonetic categorization 2006). However very little is known regarding the mechanisms that guide phonetic learning in adults. Despite initial nondiscriminability, adults can learn to distinguish new phonetic contrasts (for, though this learning is limited to achieving performance levels well below native levels. A well-studied example concerns learning of the English /r/-/l/ distinction by Japanese adults. American English /r/ differs mostly from /l/ in the frequency of the third …