Student's Self-Reported Experience of Soundscape: The Link between Noise, Psychological and Physical Well-Being.

Extensive research has shown that noise has detrimental effects on learning in classrooms, yet schools remain noisy environments. In addition, little is known about the students' insight into their subjective reaction to noise. Students' awareness of noise, as well as their perception of its effects on their affective and bodily states, remain unanswered. In the current study, the self-reported experience of noise and reaction towards noise, which was collected by way of a questionnaire, was assessed for 408 students in primary and secondary schools in Québec. Results suggest that about half of the students experience affective and bodily reactions to noise, and students who report having a negative affective reaction to noise are also more prone to report feeling this noise in their bodies. The results of this study offer a comprehensive picture of the students' subjective (affective and bodily) state in relation to noise in schools.

Time course of EEG complexity reflects attentional engagement during listening to speech in noise.

Auditory distractions are recognized to considerably challenge the quality of information encoding during speech comprehension. This study explores electroencephalography (EEG) microstate dynamics in ecologically valid, noisy settings, aiming to uncover how these auditory distractions influence the process of information encoding during speech comprehension. We examined three listening scenarios: (1) speech perception with background noise (LA), (2) focused attention on the background noise (BA), and (3) intentional disregard of the background noise (BUA). Our findings showed that microstate complexity and unpredictability increased when attention was directed towards speech compared with tasks without speech (LA > BA & BUA). Notably, the time elapsed between the recurrence of microstates increased significantly in LA compared with both BA and BUA. This suggests that coping with background noise during speech comprehension demands more sustained cognitive effort. Additionally, a two-stage time course for both microstate complexity and alpha-to-theta power ratio was observed. Specifically, in the early epochs, a lower level was observed, which gradually increased and eventually reached a steady level in the later epochs. The findings suggest that the initial stage is primarily driven by sensory processes and information gathering, while the second stage involves higher level cognitive engagement, including mnemonic binding and memory encoding.

Parkinson's disease affects the neural alpha oscillations associated with speech-in-noise processing.

Parkinson's disease (PD) has increasingly been associated with auditory dysfunction, including alterations regarding the control of auditory information processing. Although these alterations may interfere with the processing of speech in degraded listening conditions, behavioural studies have generally found preserved speech-in-noise recognition in PD. However, behavioural speech audiometry does not capture the neurophysiological mechanisms supporting speech-in-noise processing. Therefore, the aim of this study was to investigate the neural oscillatory mechanisms associated with speech-in-noise processing in PD. Twelve persons with PD and 12 age- and gender-matched healthy controls (HCs) were included in this study. Persons with PD were studied in the medication off condition. All subjects underwent an audiometric screening and performed a sentence-in-noise recognition task under simultaneous electroencephalography (EEG) recording. Behavioural speech recognition scores and self-reported ratings of effort, performance, and motivation were collected. Time-frequency analysis of EEG data revealed no significant difference between persons with PD and HCs regarding delta-theta (2-8 Hz) inter-trial phase coherence to noise and sentence onset. In contrast, significantly increased alpha (8-12 Hz) power was found in persons with PD compared with HCs during the sentence-in-noise recognition task. Behaviourally, persons with PD demonstrated significantly decreased speech recognition scores, whereas no significant differences were found regarding effort, performance, and motivation ratings. These results suggest that persons with PD allocate more cognitive resources to support speech-in-noise processing. The interpretation of this finding is discussed in the context of a top-down mediated compensation mechanism for inefficient filtering and degradation of auditory input in PD.

The Dutch Main Concept Analysis: Translation and Establishment of Normative Data.

Purpose The main concept analysis (MCA; Kong, 2009) quantifies the effectiveness and efficiency of information transfer during verbal discourse by means of four sets of sequential pictorial stimuli. This test was originally developed for a Cantonese-speaking population. The main goals of this study were (a) to translate and adapt the MCA to Dutch; (b) to establish normative data for healthy native Dutch-speaking adults; (c) to assess the effect of age, education level, and gender on MCA outcome; and (d) to establish inter- and intrarater reliability of the Dutch MCA. Method Language samples were collected from 60 healthy native Dutch speakers, equally recruited in different age (20-39 years, 40-59 years, 60-79 years) and education (middle and highly educated) categories through administration of the MCA. Utterances produced by at least 75% of the participants were included as a main concept in the Dutch MCA. Subsequently, age-specific normative data were established for each of the MCA parameters. Finally, an ICC was calculated in order to verify inter- and intrarater reliability of the Dutch MCA. Results The translated MCA consisted of 19 main concepts. Age-specific normative data were obtained. Both age and education level had a significant effect on MCA outcome. Information transfer in elderly was both less effectively and efficiently compared to young- and middle-aged adults. In addition, highly educated participants transferred information less efficiently compared to middle educated participants. Based on inter- and intrarater reliability measures, the Dutch MCA proved to be a reliable measuring instrument. Conclusions The MCA was translated to Dutch, and age-specific normative data were established for a healthy, Dutch-speaking population. The Dutch MCA is a reliable tool for eliciting and quantifying discourse production. Validation of the test for people with aphasia is necessary in order for the test to be useful in a clinical practice.

Evaluation of multi-feature auditory deviance detection in Parkinson's disease: a mismatch negativity study.

Behavioral studies on auditory deviance detection in patients with Parkinson's disease (PD) have reported contradictory results. The primary aim of this study was to investigate auditory deviance detection of multiple auditory features in patients with PD by means of objective and reliable electroencephalographic (EEG) measurements. Twelve patients with early-stage PD and twelve age- and gender-matched healthy controls (HCs) were included in this study. Patients with PD participated without their regular dopaminergic medication. All subjects underwent an audiometric screening and performed a passive multi-feature mismatch negativity (MMN) paradigm. Repeated-measures analysis of variance (ANOVA) demonstrated no significant differences between patients with PD and HCs regarding MMN mean amplitude and latency for frequency, duration and gap deviants. Nevertheless, a trend towards increased MMN mean amplitude and latency was found in response to intensity deviants in patients with PD compared to HCs. Increased intensity MMN amplitude may indicate that more neural resources are allocated to the processing of intensity deviances in patients with PD compared to HCs. The interpretation of this intensity-specific MMN alteration is further discussed in the context of a compensatory mechanism for auditory intensity processing and involuntary attention switching in PD.

The Effect of Parkinson's Disease on Otoacoustic Emissions and Efferent Suppression of Transient Evoked Otoacoustic Emissions.

Purpose Several studies have demonstrated increased auditory thresholds in patients with Parkinson's disease (PD) based on subjective tonal audiometry. However, the pathophysiological mechanisms underlying auditory dysfunction in PD remain elusive. The primary aim of this study was to investigate cochlear and olivocochlear function in PD using objective measurements and to assess the effect of dopaminergic medication on auditory function. Method Eighteen patients with PD and 18 gender- and age-matched healthy controls (HCs) were included. Patients with PD participated in medication on and off conditions. Linear mixed models were used to determine the effect of PD on tonal audiometry, transient evoked and distortion product otoacoustic emissions (OAEs), and efferent suppression (ES). Results Tonal audiometry revealed normal auditory thresholds in patients with PD for their age across all frequencies. OAE signal amplitudes demonstrated a significant interaction effect between group (PD vs. HC) and frequency, indicating decreased OAEs at low frequencies and increased OAEs at high frequencies in patients with PD. No significant differences were found between patients with PD and HCs regarding ES. In addition, no significant effect of medication status was found on auditory measurements in patients with PD. Conclusions Altered OAEs support the hypothesis of cochlear alterations in PD. No evidence was found for the involvement of the medial olivocochlear system. Altogether, OAEs may provide an objective early indicator of auditory alterations in PD and should complement subjective tonal audiometry when assessing and monitoring auditory function in PD.

Neurophysiological investigation of auditory intensity dependence in patients with Parkinson's disease.

There is accumulating evidence for auditory dysfunctions in patients with Parkinson's disease (PD). Moreover, a possible relationship has been suggested between altered auditory intensity processing and the hypophonic speech characteristics in PD. Nonetheless, further insight into the neurophysiological correlates of auditory intensity processing in patients with PD is needed primarily. In the present study, high-density EEG recordings were used to investigate intensity dependence of auditory evoked potentials (IDAEPs) in 14 patients with PD and 14 age- and gender-matched healthy control participants (HCs). Patients with PD were evaluated in both the on- and off-medication states. HCs were also evaluated twice. Significantly increased IDAEP of the N1/P2 was demonstrated in patients with PD evaluated in the on-medication state compared to HCs. Distinctive results were found for the N1 and P2 component. Regarding the N1 component, no differences in latency or amplitude were shown between patients with PD and HCs regardless of the medication state. In contrast, increased P2 amplitude was demonstrated in patients with PD evaluated in the on-medication state compared to the off-medication state and HCs. In addition to a dopaminergic deficiency, deficits in serotonergic neurotransmission in PD were shown based on increased IDAEP. Due to specific alterations of the N1-P2 complex, the current results suggest deficiencies in early-attentive inhibitory processing of auditory input in PD. This interpretation is consistent with the involvement of the basal ganglia and the role of dopaminergic and serotonergic neurotransmission in auditory gating.

EEG Correlates of Learning From Speech Presented in Environmental Noise.

How the human brain retains relevant vocal information while suppressing irrelevant sounds is one of the ongoing challenges in cognitive neuroscience. Knowledge of the underlying mechanisms of this ability can be used to identify whether a person is distracted during listening to a target speech, especially in a learning context. This paper investigates the neural correlates of learning from the speech presented in a noisy environment using an ecologically valid learning context and electroencephalography (EEG). To this end, the following listening tasks were performed while 64-channel EEG signals were recorded: (1) attentive listening to the lectures in background sound, (2) attentive listening to the background sound presented alone, and (3) inattentive listening to the background sound. For the first task, 13 lectures of 5 min in length embedded in different types of realistic background noise were presented to participants who were asked to focus on the lectures. As background noise, multi-talker babble, continuous highway, and fluctuating traffic sounds were used. After the second task, a written exam was taken to quantify the amount of information that participants have acquired and retained from the lectures. In addition to various power spectrum-based EEG features in different frequency bands, the peak frequency and long-range temporal correlations (LRTC) of alpha-band activity were estimated. To reduce these dimensions, a principal component analysis (PCA) was applied to the different listening conditions resulting in the feature combinations that discriminate most between listening conditions and persons. Linear mixed-effect modeling was used to explain the origin of extracted principal components, showing their dependence on listening condition and type of background sound. Following this unsupervised step, a supervised analysis was performed to explain the link between the exam results and the EEG principal component scores using both linear fixed and mixed-effect modeling. Results suggest that the ability to learn from the speech presented in environmental noise can be predicted by the several components over the specific brain regions better than by knowing the background noise type. These components were linked to deterioration in attention, speech envelope following, decreased focusing during listening, cognitive prediction error, and specific inhibition mechanisms.

Future Perspectives on the Relevance of Auditory Markers in Prodromal Parkinson's Disease.

Research on auditory processing in Parkinson's disease (PD) has recently made substantial progress. At present, evidence has been found for altered auditory processing in the clinical stage of PD. The auditory alterations in PD have been demonstrated with low-cost and non-invasive assessments that are already used in routine clinical practice. Since auditory alterations have been reported early in disease progression, it would be highly relevant to investigate whether auditory markers could be provided in the prodromal stage of PD. In addition, auditory alterations in early stage PD might be modulated by dopaminergic medication. Therefore, the aim of this review is (1) to summarize the literature on auditory processing in PD with a specific focus on the early disease stages, (2) to give future perspectives on which audiological and electrophysiological measurements could be useful in the prodromal stage of PD and (3) to assess the effect of dopaminergic medication on potential auditory markers in the prodromal stage of PD.

Central auditory processing in parkinsonian disorders: A systematic review.

Altered auditory processing has been increasingly recognized as a non-motor feature in parkinsonian disorders. This systematic review provides an overview of behavioral and electrophysiological literature on central auditory processing in patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). A systematic database search was conducted and yielded 88 studies that met the intelligibility criteria. The collected data revealed distinct impairments in a range of central auditory processes in PD, including altered deviance detection of basic auditory features, auditory brainstem processing, auditory gating and selective auditory attention. In contrast to PD, literature on central auditory processing in atypical parkinsonian disorders was relatively scarce, but provided some evidence for impaired central auditory processing in MSA and PSP. The interpretation of these findings is discussed and suggestions for further research are offered.

Analysis of probe fitting stimulus properties on transient evoked otoacoustic emissions.

Objective: The objectives of the current study are first, to evaluate the subjective evaluation of probe fitting stimulus properties, and second, to analyse the effects of different probe fittings on transient evoked otoacoustic emission (TEOAE) response and noise amplitudes in subjects.Design: The Q methodology was used to sort 48 probe fittings differing in stimulus properties in seven categories from totally unacceptable to certainly acceptable. Further, TEOAE response and noise amplitudes were measured in one baseline condition with optimal probe fitting and eight experimental conditions with less than optimal probe fittings.Study sample: The probe fittings were ranked by 18 participants, while the repeated measures design was performed in 34 ear.Results: First, it was found that only 19.61% of all distributions of the probe fittings by the participants had a mutual correlation of at least 70.00%. Almost 60% of the variance of distributions was explained by 83.33% of the participants, although most probe fittings significantly differed from other fittings based on spectral broadness. Second, significant differences in TEOAE response and especially noise amplitudes between conditions were found. Further, TEOAE response and noise amplitudes between the baseline and experimental conditions were significantly different depending on ringing and spectral flatness of the stimulus.Conclusion: A substantial amount of subjectivity during TEOAE measurements is involved with regard to the evaluation of probe fitting stimulus properties. TEOAE response but especially noise amplitudes are influenced by varying stimulus parameters which stresses the importance of inspecting these parameters prior to or during EOAE measurements. Although more research is needed, some guidelines regarding these parameters are given which could improve the accuracy of TEOAEs in practice.

Comparison of land use regression and random forests models on estimating noise levels in five Canadian cities.

Chronic exposure to environment noise is associated with sleep disturbance and cardiovascular diseases. Assessment of population exposed to environmental noise is limited by a lack of routine noise sampling and is critical for controlling exposure and mitigating adverse health effects. Land use regression (LUR) model is newly applied in estimating environmental exposures to noise. Machine-learning approaches offer opportunities to improve the noise estimations from LUR model. In this study, we employed random forests (RF) model to estimate environmental noise levels in five Canadian cities and compared noise estimations between RF and LUR models. A total of 729 measurements and 33 built environment-related variables were used to estimate spatial variation in environmental noise at the global (multi-city) and local (individual city) scales. Leave one out cross-validation suggested that noise estimates derived from the RF global model explained a greater proportion of variation (R2: RF = 0.58, LUR = 0.47) with lower root mean squared errors (RF = 4.44 dB(A), LUR = 4.99 dB(A)). The cross-validation also indicated the RF models had better general performance than the LUR models at the city scale. By applying the global models to estimate noise levels at the postal code level, we found noise levels were higher in Montreal and Longueuil than in other major Canadian cities.

Systematic Audiological Assessment of Auditory Functioning in Patients With Parkinson's Disease.

Purpose Alterations in primary auditory functioning have been reported in patients with Parkinson's disease (PD). Despite the current findings, the pathophysiological mechanisms underlying these alterations remain unclear, and the effect of dopaminergic medication on auditory functioning in PD has been explored insufficiently. Therefore, this study aimed to systematically investigate primary auditory functioning in patients with PD by using both subjective and objective audiological measurements. Method In this case-control study, 25 patients with PD and 25 age-, gender-, and education-matched healthy controls underwent an audiological test battery consisting of tonal audiometry, short increment sensitivity index, otoacoustic emissions (OAEs), and speech audiometry. Patients with PD were tested in the on- and off-medication states. Results Increased OAE amplitudes were found when patients with PD were tested without dopaminergic medication. In addition, speech audiometry in silence and multitalker babble noise demonstrated higher phoneme scores for patients with PD in the off-medication condition. The results showed no differences in auditory functioning between patients with PD in the on-medication condition and healthy controls. No effect of disease stage or motor score was evident. Conclusions This study provides evidence for a top-down involvement in auditory processing in PD at both central and peripheral levels. Most important, the increase in OAE amplitude in the off-medication condition in PD is hypothesized to be linked to a dysfunction of the olivocochlear efferent system, which is known to have an inhibitory effect on outer hair cell functioning. Future studies may clarify whether OAEs may facilitate an early diagnosis of PD.

Mobile phones: A trade-off between speech intelligibility and exposure to noise levels and to radio-frequency electromagnetic fields.

When making phone calls, cellphone and smartphone users are exposed to radio-frequency (RF) electromagnetic fields (EMFs) and sound pressure simultaneously. Speech intelligibility during mobile phone calls is related to the sound pressure level of speech relative to potential background sounds and also to the RF-EMF exposure, since the signal quality is correlated with the RF-EMF strength. Additionally, speech intelligibility, sound pressure level, and exposure to RF-EMFs are dependent on how the call is made (on speaker, held at the ear, or with headsets). The relationship between speech intelligibility, sound exposure, and exposure to RF-EMFs is determined in this study. To this aim, the transmitted RF-EMF power was recorded during phone calls made by 53 subjects in three different, controlled exposure scenarios: calling with the phone at the ear, calling in speaker-mode, and calling with a headset. This emitted power is directly proportional to the exposure to RF EMFs and is translated into specific absorption rate using numerical simulations. Simultaneously, sound pressure levels have been recorded and speech intelligibility has been assessed during each phone call. The results show that exposure to RF-EMFs, quantified as the specific absorption in the head, will be reduced when speaker-mode or a headset is used, in comparison to calling next to the ear. Additionally, personal exposure to sound pressure is also found to be highest in the condition where the phone is held next to the ear. On the other hand, speech perception is found to be the best when calling with a phone next to the ear in comparison to the other studied conditions, when background noise is present.

Presenting and processing information in background noise: A combined speaker-listener perspective.

Transferring information orally in background noise is challenging, for both speaker and listener. Successful transfer depends on complex interaction between characteristics related to listener, speaker, task, background noise, and context. To fully assess the underlying real-life mechanisms, experimental design has to mimic this complex reality. In the current study, the effects of different types of background noise have been studied in an ecologically valid test design. Documentary-style information had to be presented by the speaker and simultaneously acquired by the listener in four conditions: quiet, unintelligible multitalker babble, fluctuating city street noise, and little varying highway noise. For both speaker and listener, the primary task was to focus on the content that had to be transferred. In addition, for the speakers, the occurrence of hesitation phenomena was assessed. The listener had to perform an additional secondary task to address listening effort. For the listener the condition with the most eventful background noise, i.e., fluctuating city street noise, appeared to be the most difficult with markedly longer duration of the secondary task. In the same fluctuating background noise, speech appeared to be less disfluent, suggesting a higher level of concentration from the speaker's side.

Modeling Speech Level as a Function of Background Noise Level and Talker-to-Listener Distance for Talkers Wearing Hearing Protection Devices.

Purpose: Studying the variations in speech levels with changing background noise level and talker-to-listener distance for talkers wearing hearing protection devices (HPDs) can aid in understanding communication in background noise. Method: Speech was recorded using an intra-aural HPD from 12 different talkers at 5 different distances in 3 different noise conditions and 2 quiet conditions. Results: This article proposes models that can predict the difference in speech level as a function of background noise level and talker-to-listener distance for occluded talkers. The proposed model complements the existing model presented by Pelegrín-García, Smits, Brunskog, and Jeong (2011) and expands on it by taking into account the effects of occlusion and background noise level on changes in speech sound level. Conclusions: Three models of the relationship between vocal effort, background noise level, and talker-to-listener distance for talkers wearing HPDs are presented. The model with the best prediction intervals is a talker-dependent model that requires the users' unoccluded speech level at 10 m as a reference. A model describing the relationship between speech level, talker-to-listener distance, and background noise level for occluded talkers could eventually be incorporated with radio protocols to transmit verbal communication only to an intended set of listeners within a given spatial range-this range being dependent on the changes in speech level and background noise level.

Field Monitoring of Otoacoustic Emissions During Noise Exposure: Pilot Study in Controlled Environment.

PURPOSE: In spite of all the efforts to implement workplace hearing conservation programs, noise-induced hearing loss remains the leading cause of disability for North American workers. Nonetheless, an individual's susceptibility to noise-induced hearing loss can be estimated by monitoring changes in hearing status in relation to the level of ambient noise exposure. The purpose of this study was to validate an approach that could improve workplace hearing conservation practices. The approach was developed using a portable and robust system designed for noisy environments and consisted of taking continuous measurements with high temporal resolution of the health status of the inner ear using otoacoustic emissions (OAEs). METHOD: A pilot study was conducted in a laboratory, exposing human subjects to industrial noise recordings at realistic levels. In parallel, OAEs were measured periodically using the designed OAE system as well as with a commercially available OAE system, used as a reference. RESULTS: Variations in OAE levels were analyzed and discussed along with the limitations of the reference and designed systems. CONCLUSIONS: This study demonstrates that the monitoring of an individual's OAEs could be useful in monitoring temporary changes in hearing status induced by exposure to ambient noise and could be considered as a new tool for effective hearing conservation programs in the workplace.

The Relationship Between Speech Production and Speech Perception Deficits in Parkinson's Disease.

Purpose: This study investigated the possible relationship between hypokinetic speech production and speech intensity perception in patients with Parkinson's disease (PD). Method: Participants included 14 patients with idiopathic PD and 14 matched healthy controls (HCs) with normal hearing and cognition. First, speech production was objectified through a standardized speech intelligibility assessment, acoustic analysis, and speech intensity measurements. Second, an overall estimation task and an intensity estimation task were addressed to evaluate overall speech perception and speech intensity perception, respectively. Finally, correlation analysis was performed between the speech characteristics of the overall estimation task and the corresponding acoustic analysis. The interaction between speech production and speech intensity perception was investigated by an intensity imitation task. Results: Acoustic analysis and speech intensity measurements demonstrated significant differences in speech production between patients with PD and the HCs. A different pattern in the auditory perception of speech and speech intensity was found in the PD group. Conclusions: Auditory perceptual deficits may influence speech production in patients with PD. The present results suggest a disturbed auditory perception related to an automatic monitoring deficit in PD.

Musician earplugs: Appreciation and protection.

Recreational music exposure is a potential risk factor for noise-induced hearing loss (NIHL). Augmented hearing protectors have been designed with modified attenuation characteristics to combine hearing protection and listening comfort. However, to date, only a few independent studies have assessed the performance of those augmented protectors in realistic exposure conditions. This study compares the listening experience and temporary effects on cochlear status with different types of earplugs after exposure to contemporary club music. Five different types of commercially available hearing protectors were worn, all commonly used during leisure-time music exposure. Four of them were augmented premolded earplugs and the fifth type was an inexpensive, standard earplug frequently distributed for free at music events. During five different test sessions of 30 min each, participants not professionally involved in music wore one particular type of protector. Contemporary club music was played at sound pressure levels (SPLs) representative of concerts and bars. After each listening session, a questionnaire on sound quality and general appreciation was completed. In addition, otoacoustic emissions (OAEs) were measured directly before and after music exposure. The reported appreciation clearly differed depending on the addressed characteristics and the specific earplug type. In this test group, the reported appreciation mainly depended on comfort and looks, while differences in sound quality were less noticeable. The changes in OAE amplitude before and after noise exposure were small in terms of clinical standards. Nevertheless, the observed temporary shifts differed systematically for the different types of hearing protectors, with two types of musician earplug showing a more systematic decline than the others. Further research with respect to actual use and achieved protection for real, unsupervised music exposure is warranted.

Annoyance, detection and recognition of wind turbine noise.

Annoyance, recognition and detection of noise from a single wind turbine were studied by means of a two-stage listening experiment with 50 participants with normal hearing abilities. In-situ recordings made at close distance from a 1.8-MW wind turbine operating at 22 rpm were mixed with road traffic noise, and processed to simulate indoor sound pressure levels at LAeq 40 dBA. In a first part, where people were unaware of the true purpose of the experiment, samples were played during a quiet leisure activity. Under these conditions, pure wind turbine noise gave very similar annoyance ratings as unmixed highway noise at the same equivalent level, while annoyance by local road traffic noise was significantly higher. In a second experiment, listeners were asked to identify the sample containing wind turbine noise in a paired comparison test. The detection limit of wind turbine noise in presence of highway noise was estimated to be as low as a signal-to-noise ratio of -23 dBA. When mixed with local road traffic, such a detection limit could not be determined. These findings support that noticing the sound could be an important aspect of wind turbine noise annoyance at the low equivalent levels typically observed indoors in practice. Participants that easily recognized wind-turbine(-like) sounds could detect wind turbine noise better when submersed in road traffic noise. Recognition of wind turbine sounds is also linked to higher annoyance. Awareness of the source is therefore a relevant aspect of wind turbine noise perception which is consistent with previous research.