PURPOSE:

The purpose of the present study was to evaluate the new Cognitive Spare Capacity Test (CSCT), which measures aspects of working memory capacity for heard speech in the audiovisual and auditory-only modalities of presentation.

METHOD:

In Experiment 1, 20 young adults with normal hearing performed the CSCT and an independent battery of cognitive tests. In the CSCT, they listened to and recalled 2-digit numbers according to instructions inducing executive processing at 2 different memory loads. In Experiment 2, 10 participants performed a less executively demanding free recall task using the same stimuli.

RESULTS:

CSCT performance demonstrated an effect of memory load and was associated with independent measures of executive function and inference making but not with general working memory capacity. Audiovisual presentation was associated with lower CSCT scores but higher free recall performance scores.

CONCLUSIONS:

CSCT is an executively challenging test of the ability to process heard speech. It captures cognitive aspects of listening related to sentence comprehension that are quantitatively and qualitatively different from working memory capacity. Visual information provided in the audiovisual modality of presentation can hinder executive processing in working memory of nondegraded speech material.

Listening to speech in noise depletes cognitive resources, affecting speech processing. The present study investigated how remaining resources or cognitive spare capacity (CSC) can be deployed by young adults with normal hearing. We administered a test of CSC (CSCT; Mishra et al., 2013) along with a battery of established cognitive tests to 20 participants with normal hearing. In the CSCT, lists of two-digit numbers were presented with and without visual cues in quiet, as well as in steady-state and speech-like noise at a high intelligibility level. In low load conditions, two numbers were recalled according to instructions inducing executive processing (updating, inhibition) and in high load conditions the participants were additionally instructed to recall one extra number, which was the always the first item in the list. In line with previous findings, results showed that CSC was sensitive to memory load and executive function but generally not related to working memory capacity (WMC). Furthermore, CSCT scores in quiet were lowered by visual cues, probably due to distraction. In steady-state noise, the presence of visual cues improved CSCT scores, probably by enabling better encoding. Contrary to our expectation, CSCT performance was disrupted more in steady-state than speech-like noise, although only without visual cues, possibly because selective attention could be used to ignore the speech-like background and provide an enriched representation of target items in working memory similar to that obtained in quiet. This interpretation is supported by a consistent association between CSCT scores and updating skills.

Individual differences in working memory capacity (WMC) are associated with speech recognition in adverse conditions, reflecting the need to maintain and process speech fragments until lexical access can be achieved. When working memory resources are engaged in unlocking the lexicon, there is less Cognitive Spare Capacity (CSC) available for higher level processing of speech. CSC is essential for interpreting the linguistic content of speech input and preparing an appropriate response, that is, engaging in conversation. Previously, we showed, using a Cognitive Spare Capacity Test (CSCT) that in young adults with normal hearing, CSC was not generally related to WMC and that when CSC decreased in noise it could be restored by visual cues. In the present study, we investigated CSC in 24 older adults with age-related hearing loss, by administering the CSCT and a battery of cognitive tests. We found generally reduced CSC in older adults with hearing loss compared to the younger group in our previous study, probably because they had poorer cognitive skills and deployed them differently. Importantly, CSC was not reduced in the older group when listening conditions were optimal. Visual cues improved CSC more for this group than for the younger group in our previous study. CSC of older adults with hearing loss was not generally related to WMC but it was consistently related to episodic long term memory, suggesting that the efficiency of this processing bottleneck is important for executive processing of speech in this group.

Purpose Seeing the talker's face improves speech understanding in noise, possibly releasing resources for cognitive processing. We investigated whether it improves free recall of spoken two-digit numbers.

Method Twenty younger adults with normal hearing and 24 older adults with hearing loss listened to and subsequently recalled lists of 13 two-digit numbers, with alternating male and female talkers. Lists were presented in quiet as well as in stationary and speech-like noise at a signal-to-noise ratio giving approximately 90% intelligibility. Amplification compensated for loss of audibility.

Results Seeing the talker's face improved free recall performance for the younger but not the older group. Poorer performance in background noise was contingent on individual differences in working memory capacity. The effect of seeing the talker's face did not differ in quiet and noise.

Conclusions We have argued that the absence of an effect of seeing the talker's face for older adults with hearing loss may be due to modulation of audiovisual integration mechanisms caused by an interaction between task demands and participant characteristics. In particular, we suggest that executive task demands and interindividual executive skills may play a key role in determining the benefit of seeing the talker's face during a speech-based cognitive task