A general working memory system for ease of language understanding (ELU, Rönnberg, 2003a) is presented. The purpose of the system is to describe and predict the dynamic interplay between explicit and implicit cognitive functions, especially in conditions of poorly perceived or poorly specified linguistic signals. In relation to speech understanding, the system based on (1) the quality and precision of phonological representations in long-term memory, (2) phonologically mediated lexical access speed, and (3) explicit, storage, and processing resources. If there is a mismatch between phonological information extracted from the speech signal and the phonological information represented in long-term memory, the system is assumed to produce a mismatch signal that invokes explicit processing resources. In the present paper, we focus on four aspects of the model which have led to the current, updated version: the language generality assumption; the mismatch assumption; chronological age; and the episodic buffer function of rapid, automatic multimodal binding of phonology (RAMBPHO). We evaluate the language generality assumption in relation to sign language and speech, and the mismatch assumption in relation to signal processing in hearing aids. Further, we discuss the effects of chronological age and the implications of RAMBPHO.

Evidence suggests that cognitive capacity predicts the ability to benefit from specific compression release settings in non-linear digital hearing instruments. Previous studies have investigated the predictive value of various cognitive tests in relation to aided speech recognition in noise using compression release settings that have been experienced for a certain period. However, the predictive value of cognitive tests with new settings, to which the user has not had the opportunity to become accustomed, has not been studied. In the present study, we compare the predictive values of two cognitive tests, reading span and letter monitoring, in relation to aided speech recognition in noise for 32 habitual hearing instrument users using new compression release settings. We found that reading span was a strong predictor of speech recognition in noise with new compression release settings. This result generalizes previous findings for experienced test settings to new test settings, for both speech recognition in noise tests used in the present study, Hagerman sentences and HINT. Letter monitoring, on the other hand, was not found to be a strong predictor of speech recognition in noise with new compression release settings.

. Cognition and aided speech recognition in noise: Specific role for cognitive factors following nine-week experience with adjusted compression settings in hearing aids. Scandinavian Journal of Psychology, 50, 405-418.The working memory model for Ease of Language Understanding (ELU) proposes that language understanding under taxing conditions is related to explicit cognitive capacity. We refer to this as the mismatch hypothesis, since phonological representations based on the processing of speech under established conditions may not be accessed so readily when input conditions change and a match becomes problematic. Then, cognitive capacity requirements may differ from those used for processing speech hitherto. In the present study, we tested this hypothesis by investigating the relationship between aided speech recognition in noise and cognitive capacity in experienced hearing aid users when there was either a match or mismatch between processed speech input and established phonological representations. The settings in the existing digital hearing aids of the participants were adjusted to one of two different compression settings which processed the speech signal in qualitatively different ways (''fast'' or ''slow''). Testing took place after a 9-week period of experience with the new setting. Speech recognition was tested under different noise conditions and with match or mismatch (i.e. alternative compression setting) manipulations of the input signal. Individual cognitive capacity was measured using a reading span test and a letter monitoring test. Reading span, a reliable measure of explicit cognitive capacity, predicted speech recognition performance under mismatch conditions when processed input was incongruent with recently established phonological representations, due to the specific hearing aid setting. Cognitive measures were not main predictors of performance under match conditions. These findings are in line with the ELU model.

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The mismatch prediction generated by the working memory framework for Ease of Language Understanding is supported for speech recognition in noise with the highly constrained Hagerman sentences but not the less-predictable HINT.