Talker-specificity and lexical competition effects during word learning

The experiments reported in this thesis examine the time-course of talker-specificity and lexical competition effects during word learning. It is typically assumed that talker-specificity effects depend on access to highly-detailed lexical representations whilst lexical competition effects depend more on abstract, overlapping representations that allow phonologically-similar words to compete during spoken word recognition. By tracking the time-course of these two effects concurrently it was possible to examine the contributions of episodic and abstract representations to recognition and processing of newly-learned words. Results indicated that talker-specific information affected recognition of both novel and existing words immediately after study, and continued to influence recognition of newly-learned words one week later. However, in the delayed test sessions talker information appeared to be less influential during recognition of recently studied existing words and novel words studied in more than one voice. In comparison, lexical competition effects for novel words were absent immediately after study but emerged one day later and remained relatively stable across the course of a week. Together the evidence is most consistent with a hybrid model of lexical representation in which episodic representations are generated rapidly, but robust abstract representations emerge only after a period of sleep-associated offline consolidation. Possible factors contributing to a change in reliance between episodic and abstract representational subsystems include the novelty of an item and the amount of variability in the input during learning. However, talker-specific lexical competition effects were observed in the one week retest, suggesting either that episodic and abstract representations were co-activated during spoken word recognition at this time point, or that perhaps talker information associated with newly-learned words was consolidated in long-term memory alongside phonological information.