Catharina Karlsson Foo

Cognition counts: a working memory system for ease of language understanding (ELU).

A general working memory system for ease of language understanding (ELU, Rönnberg, ) 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.

Phonological mismatch and explicit cognitive processing in a sample of 102 hearing-aid users

Rudner et al () showed that when compression release settings are manipulated in the hearing instruments of Swedish habitual users, the resulting mismatch between the phonological form of the input speech signal and representations stored in long-term memory leads to greater engagement of explicit cognitive processing under taxing listening conditions. The mismatch effect is manifest in significant correlations between performance on cognitive tests and aided-speech-recognition performance in modulated noise and/or with fast compression release settings. This effect is predicted by the ELU model (Rönnberg et al, 2008). In order to test whether the mismatch effect can be generalized across languages, we examined two sets of aided speech recognition data collected from a Danish population where two cognitive tests, reading span and letter monitoring, had been administered. A reanalysis of all three datasets, including 102 participants, demonstrated the mismatch effect. These findings suggest that the effect of phonological mismatch, as predicted by the ELU model ( et al, this issue) and tapped by the reading span test, is a stable phenomenon across these two Scandinavian languages.

Phonological mismatch makes aided speech recognition in noise cognitively taxing.

Objectives: The working memory framework for Ease of Language Understanding predicts that speech processing becomes more effortful, thus requiring more explicit cognitive resources, when there is mismatch between speech input and phonological representations in long-term memory. To test this prediction, we changed the compression release settings in the hearing instruments of experienced users and allowed them to train for 9 weeks with the new settings. After training, aided speech recognition in noise was tested with both the trained settings and orthogonal settings. We postulated that training would lead to acclimatization to the trained setting, which in turn would involve establishment of new phonological representations in long-term memory. Further, we postulated that after training, testing with orthogonal settings would give rise to phonological mismatch, associated with more explicit cognitive processing. Design: Thirty-two participants (mean = 70.3 years, SD = 7.7) with bilateral sensorineural hearing loss (pure-tone average = 46.0 dB HL, SD = 6.5), bilaterally fitted for more than 1 year with digital, two-channel, nonlinear signal processing hearing instruments and chosen from the patient population at the Linköoping University Hospital were randomly assigned to 9 weeks training with new, fast (40 ms) or slow (640 ms), compression release settings in both channels. Aided speech recognition in noise performance was tested according to a design with three within-group factors: test occasion (T1, T2), test setting (fast, slow), and type of noise (unmodulated, modulated) and one between-group factor: experience setting (fast, slow) for two types of speech materials—the highly constrained Hagerman sentences and the less-predictable Hearing in Noise Test (HINT). Complex cognitive capacity was measured using the reading span and letter monitoring tests. Prediction: We predicted that speech recognition in noise at T2 with mismatched experience and test settings would be associated with more explicit cognitive processing and thus stronger correlations with complex cognitive measures, as well as poorer performance if complex cognitive capacity was exceeded. Results: Under mismatch conditions, stronger correlations were found between performance on speech recognition with the Hagerman sentences and reading span, along with poorer speech recognition for participants with low reading span scores. No consistent mismatch effect was found with HINT. Conclusions: 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.