In this dissertation, the traditional dichotic listening paradigm was integrated with the notion of working memory capacity (WMC) to explore the cognitive mechanism of bilingual speech comprehension at the passage level. A bilingual dichotic listening (BDL) task was developed and administered to investigate characteristics of bilingual listening comprehension, which include semantic relatedness, unattended language, ear preference, auditory attentional control, executive control, voluntary note-taking, and language switching. The central concept of the BDL paradigm is that the auditory stimuli are presented in the bilinguals’ two languages and their attention is directed to one of their ears while they have to overcome cognitive and linguistic conflicts caused by information in the other ear. Different experimental manipulations were employed in the BDL task to examine the characteristics of bilingual listening comprehension. The bilingual population examined was Japanese- English bilinguals with relatively high second language (L2) proficiency and WMC. Seven experiments and seven cross-experimental comparisons are reported. Experiment 1 employed the BDL task with pairs of passages that had different semantic relationships (i.e., related or unrelated) and were heard in different languages (i.e., L1 or L2). The semantically related passages were found to interfere with comprehension of the attended passage more than the semantically unrelated passages, whether the attended and unattended languages were the same or different. Contrary to the theories of bilingual language control, unattended L1 was found to enhance comprehension of the attended passage, regardless of semantic relationships and language it was heard in. L2 proficiency and WMC served as good predictors of resolution of the cognitive and linguistic conflicts. The BDL task is suggested to serve as an experimental paradigm to explore executive control and language control in bilingual speech comprehension. Experiment 2 was conducted to investigate language lateralisation (i.e., ear preference) on bilingual speech comprehension, hence, the participants in Experiment 1 used their preferred ear, whereas participants in Experiment 2 used their non-preferred ear, whether it was left or right, in the BDL task. Comprehension was better through the preferred ear, indicating that there is a favourable ear-to-hemisphere route for understanding bilinguals’ two languages. Most of the participants were found to be left-lateralised (i.e., right-eared) and some to be right-lateralised (i.e., left-eared) presumably depending on their L2 proficiency and WMC. Experiment 3 was concerned with auditory attentional control, and explored whether there would be a right-ear advantage (REA). The participants indicated an REA whether the attended and unattended languages were L1 or L2. When they listened to Japanese in the left ear, they found it more difficult to suppress Japanese in the right ear than English. WMC was not required as much as expected for auditory attentional control probably because the passages in Experiment 3 did not yield as much semantic competition as those in Experiment 1. L2 proficiency was crucial for resolving within- and between-language competition in each ear. Experiments 4, 5, and 6 were replications of Experiments 1, 2 and 3, but these latter experiments considered the effect of note-taking that is commonly performed in everyday listening situations. Note-taking contributed to better performance and clearer understanding of the role of WMC in bilingual speech comprehension. A cross-experimental analysis between Experiments 1, 2, 4, and 5 revealed not only a facilitatory role of note-taking in bilingual listening comprehension in general, but also a hampering role when listening through the preferred ear. Experiment 7 addressed the effect of predictability of language switching by presenting L1 and L2 in a systematic order while switching attention between ears and comparing the result with that of Experiment 6 where language switching was unpredictable. The effect of predictability of language switching was different between ears. When language switches were predictable, higher comprehension was observed in the left ear than the right ear, and when language switches were unpredictable, higher comprehension was observed in the right ear than the left ear, thereby suggesting a mechanism of asymmetrical language control. WMC was more related to processing of predictable language switches than that of unpredictable language switches. The dissertation ends with discussions of the implications from the seven BDL experiments and possible applications, along with experimental techniques from other relevant disciplines that might be used in future research to yield additional insight into how bilingual listeners sustain their listening performance in their two languages in the real-life situations.

published_or_final_version / abstract / Speech and Hearing Sciences / Master / Master of Science in Audiology

Dichotic tests evaluate binaural integration through simultaneous presentation of different stimuli to each ear of a listener who has normal hearing sensitivity in both ears. Dichotic listening deficits may lead to problems with language, communication, reading, or academic performance. If accurately identified, dichotic deficits may be treatable with listening training or managed with accommodation. However, it is not clear which of several commercially-available dichotic test recordings are best for audiologists to use when assessing binaural integration in children. Literature review revealed limited evidence of reliability, accuracy, usefulness, or value for dichotic tests applied to children. Of 11 dichotic tests identified, five reported some evidence of test-retest reliability. Correlation between results on repeated administration was moderate to good (r=0.59 to 0.92). Evidence of accuracy was identified for 5 tests but was not generalizable due to significant limitations in study design. No evidence was found to either support or dispute claims of usefulness or value. Since reliability is a necessary prerequisite for good test performance, we sought to directly compare test-retest reliability for three dichotic measures: SCAN-3 Competing Words (CW), Musiek's Double Dichotic Digits (DD-M), and Bergen Dichotic Listening Test with Consonant-Vowel Syllables (CV-B). Sixty English-speaking children, 7-14 years old with normal hearing, had a single study-visit during which each test was administered twice. Changes on retest were compared to binomial model predictions, summarized by within-subject standard deviation (Sw), and compared among tests. Correlates of variance were explored. All 3 tests had reliability within bounds predicted by binomial model. Forty-item scores were more reliable (Sw=5%) than those based on 20-30 items (Sw=6-8%). No associations between participant characteristics and reliability were found. CW and DD-M were evaluated for evidence of agreement and decision consistency. Although participants were rank ordered similarly by right ear (ρ = 0.58), left ear (ρ = 0.51) and total (ρ = 0.73) scores, the tests did not agree on ranking by inter-aural asymmetry (ρ =0.18). CW and DD-M did not agree on direction of ear advantage (κ = 0.01, p = 0.93) and had poor agreement on which children displayed dichotic deficits (κ = 0.22, p < 0.01). DD identified significantly more participants with deficits (n=18) than CW (n=3) (p < 0.001). Although dichotic procedures show moderate reliability, their precision is limited. Assessment of their accuracy is limited by the absence of a widely-accepted gold standard reference test, but two commonly used tests failed to agree on which children had deficits. The data do not yet support routine clinical use of dichotic tests of binaural integration with children. Additional research is needed to determine if there are any conditions under which dichotic procedures demonstrate usefulness or value.

Diss. Linköping : Universitetet, 2005.

The new compact disc from the Department of Veterans Affairs, Tonal and Speech Materials for Auditory Perceptual Assessment, Disc 2.0 (1998), contains two lists of randomly interleaved 1-, 2-, and 3-pair dichotic digits. Two experiments are reported, in which the effects of low-pass filtering and inter-digit interval on dichotic digit recognition were investigated in adult listeners with normal hearing and with mild-to-moderate cochlear hearing loss. Results demonstrated that in the filtered condition, as the low-pass cutoff was increased, there was an increase in recognition performance for 1-, 2-, and 3-pair dichotic digits. When compared to normative data for the materials, findings indicate that the interleaved 1-, 2-, and 3-pair dichotic digit materials were essentially resistant to the effects of hearing loss. There was no significant change in recognition performance as a function of inter-digit interval. The studied 625-ms range of inter-digit intervals studied produced consistent recognition performance with both groups of listeners.

Dichotic listening was evaluated in free-recall and directed-recall (pre-cued, post-cued) response conditions using interleaved one-, two-, and three-pair dichotic digit materials. In the free-recall condition, the subjects recalled in any order the digits presented. In the directed-recall condition, a response task was examined where subjects recalled all digits presented to the cued ear (pre- or post-cued) followed by the digits presented to the opposite (non-cued) ear. Thirty 20- to 29-year-old adults with normal hearing and 30 60- to 79-year-old adults with mild-to-moderate sensorineural hearing loss were evaluated. In all conditions, performance by the younger listeners was better than performance by the elderly listeners. As the difficulty of the dichotic digit task increased, recognition performance decreased. The recognition performance of elderly listeners was more affected by increases in the difficulty of the stimulus materials as compared to the younger listeners. In the free-recall condition, there was a right-ear advantage for both age groups. When instructional bias was imposed, the results favored the ear of instructed bias. The differences in recognition performance between young and elderly listeners likely reflect differences in the difficulty of the dichotic digit test conditions and variations in the demand on auditory memory.

Purpose: To establish normative data for children and to characterize developmental differences in performance with the free recall version of the Randomized Dichotic Digits Test. Research Design: Group comparison of behavioral data derived from administration of the Randomized Dichotic Digits Test. Study Sample: Children from 10 to 18 years of age (167) and young adults from 19 to 28 years of age (50). Results: Performance improved with age across all types of digit pairs, especially in the left ear, leading to smaller interaural asymmetries among older participants. A left-ear advantage was produced by 39 subjects (18%), only two of whom were left-handed. Normative data are reported for right and left ear scores and for interaural asymmetry (percent correct difference between the two ears) under one-, two-, and three-pair conditions of the test and for interaural asymmetry across the entire test. A unilateral deficit was identified in children (15.5%) and young adults (12%) for the left ear and in children (11.3%) and young adults (6%) for the right ear. A bilateral deficit was also identified in children (6.5%) and young adults (6%). Conclusions: This test may be useful as part of the clinical battery for identifying binaural integration weaknesses and referring individuals for auditory rehabilitation for interaural asymmetry (ARIA).

Yes / Purpose: Listening-related fatigue is a potential negative consequence of challenges experienced during everyday listening, and may disproportionately affect older adults. Contrary to expectation, we recently found that increased reports of listening-related fatigue were associated with better performance on a dichotic listening task (McGarrigle et al., 2021a). However, this link was found only in individuals who reported heightened sensitivity to a variety of physical, social, and emotional stimuli (i.e., increased ‘sensory-processing sensitivity’; SPS). The current study examined whether perceived effort may underlie the link between performance and fatigue. Methods: 206 young adults, aged 18-30 years (Experiment 1) and 122 older adults, aged 60-80 years (Experiment 2) performed a dichotic listening task and were administered a series of questionnaires including: the NASA task load index of perceived effort, the Vanderbilt Fatigue Scale (measuring daily life listening-related fatigue) and the Highly Sensitive Person Scale (measuring SPS). Both experiments were completed online. Results: SPS predicted listening-related fatigue but perceived effort during the listening task was not associated with SPS or listening-related fatigue in either age group. We were also unable to replicate the interaction between dichotic listening performance and SPS in either group. Exploratory analyses revealed contrasting effects of age; older adults found the dichotic listening task more effortful, but indicated lower overall fatigue. Conclusions: These findings suggest that SPS is a better predictor of listening-related fatigue than performance or effort ratings on a dichotic listening task. SPS may be an important factor in determining an individual’s likelihood of experiencing listening-related fatigue irrespective of hearing or cognitive ability. / This research was supported by an ESRC New Investigator Award (ES/R003572/1) to Ronan McGarrigle.

This experiment tested three hypotheses linking the right cerebral regulation of hostility and physiological arousal. First, replication of previous research supporting heightened physiological (systolic blood pressure, diastolic blood pressure, and heart rate) reactivity among high hostile subjects was attempted. Second, a positive association between hostility and reactivity of facial valence and intensity to stress were expected. Last, hemispheric lateralization of cerebral activity in response to stress was measured. Low- and high-hostile subjects were identified using the Cook Medley Hostility Scale (CMHS). All subjects completed the cold pressor paradigm and were videotaped before, during, and after the stressor for analysis of facial valence and intensity. Physiological measures (SBP, DBP, and HR) were recorded and dichotic listening procedures were administered before and after the stressor. The primary finding of this research was greater right cerebral activation to stress among high-hostile subjects, as indicated by their enhanced intention to the left ear. Data further supported previous findings of heightened physiological reactivity to stress among high-hostiles. However, no hostility group differences on facial expression measures were found. Data suggest a positive relationship between right cerebral activity and cardiovascular arousal. / Master of Science

The Dichotic Emotional Words Tape developed by Bryden and MacCrae (1989) was used to assess cerebral asymmetry for propositional and nonpropositional speech as a function of verbal fluency. Forty-five right-handed subjects with normal auditory acuity for pure tones were assigned to a verbal fluency classification based on scores on the FAS test (Borkowski, Benton, & Spreen, 1967). After being assigned to a fluency category, subjects were instructed to listen for a word (bower, dower, power, or tower) or affective tone (happy, sad, angry, or neutral). The most important findings of this study were the main effects of fluency (higher, middle, and lower), stimulus type (word and affect), and focus or intention (focus left and focus right). Subjects higher in fluency exhibited significantly greater REA and LEA scores than subjects lower in fluency. For stimuli presented to the right ear, scores for words were significantly greater than scores for affect. However, for stimuli presented to the left ear, scores for affect were significantly greater than scores for words. Focus left instructions led to increases in LEA scores, while focus right instructions led to increases in REA scores. Directions for future research are discussed. / Master of Science