Distance judgement in individuals with vision and hearing loss

Abstract

Distance judgement is essential for safe navigation. People with vision loss (VL) increasingly rely on hearing for distance judgement. However, it is unclear how well auditory cues compensate for visual deficits, especially in those with additional hearing loss (dual sensory loss, DSL). This study evaluated the visual, auditory and audiovisual distance judgement in VL and DSL, by both verbally estimating and walking to remembered target locations. Fifty adults (16 controls, 19 VL, 15 DSL) estimated the distances of visual, auditory, and audiovisual targets across six distances (0.9–5.4 m) in a normal acoustic room, by verbally report the distances or walk to the perceived locations. The visual stimuli were flashing red lights. The auditory stimuli were pulsing tones. Accuracy was measured with root mean squared error, and bias was assessed by regression slopes between actual and estimated distances. In our task, visual judgement remained accurate among VL and DSL participants, matching controls. Auditory estimates showed greater errors and biases for all groups, especially for DSL. With audiovisual cues, the VL and DSL groups performed worse than using vision alone. The agreement between verbal reports and walking responses were strong for visual and audiovisual conditions (r² > 0.80) but weak for the auditory condition (r² < 0.37). For individuals with VL or DSL, vision may remain a more robust sense for distance judgment. Auditory distance judgement in our study showed greater errors, which increased in those with hearing loss. For the VL and DSL groups, audiovisual performance can be poorer than vision alone, possibly due to insufficient integration or overreliance on hearing. Verbal reports are valid proxies for walking responses in visual distance judgement but not for auditory localization. Measuring the relative strengths of vision and hearing is crucial for developing individualized strategies to support distance judgment in individuals with sensory loss.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1038/s41598-026-61622-3.

Introduction

Spatial localization refers to the ability to judge the location of people or objects in relation to oneself. Spatial localization is essential for safe mobility and social engagement, allowing individuals to avoid hazards and navigate effectively within dynamic environments¹. Individuals with vision loss (VL) have been reported to experience increased difficulty with spatial localization and orientation², such as detecting the ramps and steps in distance^3,4, judging the position of an object located straight-ahead⁵, and learning spatial layout⁶ (i.e., the ability to perceive, organize and remember the arrangement of objects in an environment).

The ability to accurately judge the distances of an object is a fundamental component of spatial localization, allowing timely and appropriate responses to environmental cues and potential hazards⁷. Humans with normal vision can judge object distances with great accuracy, which relies on various visual cues, such as relative size, relative height, occlusion, and binocular disparity^8,9. These cues vary in reliability and effective range: binocular disparity, vergence, and accommodation are most useful at near distances, whereas other cues such as relative size, occlusion, texture gradients, and linear perspective support judgments over longer distances¹⁰. Similarly, auditory distance perception can also rely on a number of cues, including sound intensity (loudness), spectral characteristics, direct-to-reverberation ratio, binaural disparity, and familiarity¹¹. Auditory distance cues are known to be generally less precise than vision and depend on the acoustic environment¹². In reality, spatial localization relies on the integration of multiple sensory modalities, especially vision and hearing for distal objects. Past research has shown that humans with normal vision and hearing tend to integrate multiple sensory cues in a statistically optimal manner by assigning more weights to the more reliable sense to optimize spatial localization performance¹³. Spatial localization has been mostly considered to rely on visual information, and the visual bias tend to dominate when both auditory and visual stimuli are produced^13,14. Among individuals with intact sensory function, distance estimates in visual-only and audiovisual conditions were more accurate and less variable than in audio-only conditions¹⁵.

While reduced vision can impair the perception of depth cues⁵, people with low vision generally update spatial information accurately, such as judging room dimensions¹⁶, but may overestimate distance traveled due to increased perception of speed of self-motion¹⁷. Research has further shown that vision loss can have cross-modal effects on sound localization, for example in judgments of “straight ahead”, indicating a shared mechanism for processing both auditory and visual cues. Further, individuals with more severe vision loss were reported to show poorer distance judgement when listening to virtual sound^18,19.

Despite the report on the cross-modal impact of vision loss on sound localization, little is known about how individuals with vision loss adapt their distance estimation strategies, particularly the extent to which they rely on non-visual cues, such as audition, when both sensory inputs are available. Additionally, low vision is frequently accompanied by hearing loss due to aging or congenital pathologies^20,21. In a prior survey study, we found that individuals with dual sensory loss (DSL) self-reported more uncertainty in deciding what sense to rely on than those with single sensory loss². How individuals with DSL utilize their residual vision and hearing for objective distance judgment is still largely unexplored.

Furthermore, methods for evaluating estimated distance perception also play a critical role in understanding an individual’s actual distance perception. Because of the importance of accurate distance judgments in everyday navigation, clinical rehabilitation, such in Orientation & Mobility training, often include distance judgement in the evaluation⁷. Verbal report of distance is frequently used to assess distance perception, due to its convenience and minimal physical demand, compared to walking¹³. In basic vision research, verbal report and walking have also been frequently compared in visual distance judgment in individuals with normal vision²². It was proposed that while verbal report has distinct sources of noises from walking, they share the same origin of perceived distance and therefore verbal report can serve as a proxy for walking²². However, whether this relation is upheld for auditory distance judgment and in those with vision and/or hearing loss is unknown.

To fill these knowledge gaps, our study examined the impact of vision and hearing loss on the visual, auditory, and audiovisual distance judgment. Participants with different types and levels of sensory impairment were asked to estimate distances using both verbal reports and walking responses under different sensory cue conditions. The primary objective was to understand how reduced vision and hearing affect distance judgment, and whether individuals with sensory loss, especially those with combined vision and hearing loss, benefit from having both sensory input while locating targets with both visual and auditory information. A secondary aim was to evaluate whether verbal estimates can serve as a practical proxy for actual walking responses, informing reliable method for distance estimation in clinical rehabilitation settings.

Methods

Participants

This study was conducted at the Envision Research Institute in collaboration with the Envision Low Vision Rehabilitation Center. Fifty participants were recruited for this study: 16 individuals with normal vision and hearing (Control; age 21–71 years old), 19 individuals with vision loss (VL; age 22–80 years old), and 15 individuals with dual sensory loss (DSL; age 37–89 years old). The study protocol was approved by the Institutional Review Board at Wichita State University, and written informed consent was obtained from all participants prior to the experiment. All research was performed in accordance with the Declaration of Helsinki, local institutional regulations, and with approval from the Institutional Review Board at Wichita State University.

The inclusion criteria were age 18 years or older; not being totally blind (i.e., retaining some form perception) or totally deaf (i.e., having some functional hearing); normal cognitive function was confirmed using the Mini-Mental State Examination (score > 24)²³; and absence of severe balance problems or residual effects from brain trauma or disease that could influence performance on the task. Balance issues were screened via the question:” Do you suffer severe dizziness or imbalance?” History of traumatic brain injury was evaluated using the 3 Question Defense and Veterans Brain Injury Center (DVBIC) Traumatic Brain Injury Screening Tool²⁴.

Vision and hearing screening

All participants underwent vision assessments of visual acuity, contrast sensitivity, visual field using a customized test⁵, as well as a hearing assessment of hearing thresholds. Participants wore their habitual corrective lenses during the vision screening and testing sessions. Monocular and binocular visual acuity and contrast sensitivity were assessed using the Lighthouse Distance Visual Acuity chart²⁵ and the Pelli–Robson contrast sensitivity chart²⁶, respectively. Pure-tone audiometry was conducted without hearing aids at frequencies of 0.5, 1, 2, 4, 6, and 8 kHz using an air conduction audiometer (240B air/bone audiometer; Amplivox, Birmingham, UK). The pure-tone average (PTA) threshold was determined as the average across 0.5, 1, 2, and 4 kHz frequencies in decibel hearing level (dB HL), following World Health Organization guidelines²⁷. In addition, since the auditory stimuli used in the current study were centered around 1 kHz (see below), the hearing threshold at 1 kHz was also analyzed separately as a frequency-specific measure of hearing threshold.

For participants with vision loss, their medical records were obtained from their low vision provider (author DCF). Our participants had heterogeneous pathologies, with the most common diagnoses being age-related macular degeneration (n = 13), retinitis pigmentosa (n = 3) and Stargardt’s disease (n = 3). For participants with hearing loss, because audiology medical records were not available, the causes of hearing loss were obtained from patients’ self-report in an intake survey. Seven of the participants with DSL reported age-related hearing loss, 3 reported hearing loss due to infection or injury, two were unsure about the cause, and two were unaware of their hearing loss. Audiograms for each participants with DSL are provided in the Supplementary Document.

Distance judgment task

Participants completed a distance estimation task in a large mobility room with symmetric dimension of 18.5 ft × 18.5 ft × 9 ft. The room’s acoustic characteristics adheres to the American Acoustic Society for education settings²⁸, containing carpeted floor, sound absorption mineral fiber ceiling panels, and gypsum wallboard. During the study, all other objects with reflective surfaces were removed from the room, with an overall estimated RT₆₀ (i.e., time required for sound pressure level to decrease by 60 dB) ranging from 0.44 s for 125 Hz to 0.25 s for 4000 Hz using Sabine’s equation²⁹. The localization stimuli were presented using pagers (Retekess TD103, Retekess, Inc., Zhengzhou, China) programmed to deliver visual, auditory, or combined audiovisual cues (see Fig. 1A). These pagers produce flashing lights and pulsing tones, chosen for their similarities to commonly used alarming devices such as smoke detectors. Six pagers were positioned at equal spaced distances (0.9 to 5.4 m) along the floor, concealed underneath black sound-transparent cloth to obscure their precise locations. This design was chosen so that the targets can be placed egocentrically straight-ahead from the participants without blocking each other, relatively easy to conceal, and intuitive as navigation targets.

Fig. 1.

(A) Schematic layout of distance judgement task. Pagers were placed at equal intervals along the floor (0.9–5.4 m from the start position). (B) Example regression lines between responded distance and actual distance to the target. Both lines have an identical root-mean squared error (RMSE = 2.05 m), but different slopes. A slope of 1 (blue) indicates proportional estimation across distances, whereas a slope of 0 (red) suggests a response bias where the same distance is chosen regardless of target location.

Three cue conditions were assessed: vision-only, audition-only, and audiovisual. In the vision-only condition, pagers emitted a circular (diameter of 8.6 cm) flashing red light constitutes 26 LED lights each at a luminance of 12 cd/m². In the audition-only condition, pagers produced a train of seven 1 kHz tones at 51 dB SPL, measured at the closest distance (0.9 m). In the audiovisual condition, both cues were presented simultaneously. Each of the light flash and sound beep lasted 200 ms, with equal interval of 600 ms in between, totaling 5 s for each presentation.

Testing was conducted under two different lighting conditions. Under normal lighting, overhead room lights were turned on (~ 500 lx). In the low lighting condition, the overhead lights were turned off and provided minimal ambient illumination (~ 10 lx) with a safety-light strip mounted at floor level around the room boundary.

For each distance and modality, participants completed two types of response. In the verbal report condition, they verbally estimated the distance to the pager in feet/inches or meters as precisely as possible, and their responses were recorded. In the walking task, participants walked to the perceived location of the pager, and the straight-line distance walked was measured with a laser distance meter. Each participant completed a total of 36 trials for the walking task and 36 trials for the verbal report task, corresponding to 6 distances presented under each lighting (i.e., normal and dark) condition and cue modality (i.e., audio, visual and audio-visual). Stimulus presentation, lighting, and report order were randomized across participants.

Five participants were hearing aids users, all were in the DSL group and used their hearing aids throughout the experiment. Four participants were white cane users but were instructed to not use their cane in the study to exclude the use of haptic cues for judging the location of the targets on the floor. The researcher (DB) followed the participants to ensure safety.

Data analysis

Datasets were analyzed using customized Python scripts. The primary aim of the analysis was to evaluate the impact of vision and hearing loss on distance judgment across cue modalities, lighting, and response types. To quantify response accuracy, we calculated the root mean squared error (RMSE) between walked distance and the presented distance for each condition. In addition, we fitted linear regression models of response distance as a function of presented distance for each participant and condition^30,31. The slope from these regressions provides a summary measure of response bias, with values closer to 1 indicating proportional estimation of the true distance, values larger than 1 indicating an expansion of perceived distances, and values smaller than 1 indicating a compression of perceived distances. Figure 1B illustrated two example regression lines with identical RMSE but different slopes. Regression slopes were estimated separately for each participant, then averaged within each group and condition.

A four-way mixed-effects ANOVA was conducted on distance judgement performance (i.e., RMSE and slope) with group (Control, VL, and DSL), cue modality (visual, auditory, and audiovisual), lighting condition (normal lighting and low lighting), and response type (walking and verbal) as factors. Given the wide age range of participants (21–89 years), age was included as a covariate in the analysis to control for potential age-related effects. Post hoc pairwise comparisons were performed using Tukey’s Honestly Significant Difference (HSD) test, which corrects for multiple comparisons. In addition, correlation analyses were performed to investigate the relationships between participants’ sensory status (i.e., visual acuity and hearing thresholds) and their distance estimation accuracy for each modality. Lastly, we assessed the correlation between verbal and walked responses under each sensory modality and lighting condition.

Results

Participant characteristics

Figure 2 illustrates the distribution of binocular visual acuity (logMAR) and pure-tone hearing thresholds (dB HL) for each group. Control participants have normal visual acuity (− 0.07 ± 0.11 logMAR), contrast sensitivity (1.93 ± 0.06 logCS) and normal hearing thresholds (4.9 ± 5.9 dB HL). The VL group has hearing thresholds similar to controls (7.6 ± 7.2 dB HL, p = 0.231) but shows reduced visual acuity (0.68 ± 0.59 logMAR, p < 0.001) and contrast sensitivity (1.06 ± 0.69 logCS, p < 0.001). The DSL group displays both elevated hearing thresholds (30.0 ± 10.5 dB HL, p < 0.001), poorer visual acuity (0.63 ± 0.54 logMAR, p < 0.001), and poorer contrast sensitivity (1.17 ± 0.55 logCS, p < 0.001). The hearing test audiograms are provided in Supplementary Fig. 1.

Fig. 2.

Distribution of binocular visual acuity (logMAR) and pure-tone hearing thresholds (dB HL) among study participants. Black circle: controls. Cyan square: vision loss. Orange triangle: dual sensory loss.

Sensory impact on distance judgement by walking response

Figure 3 illustrates the average responses as a function of the actual target distances for each group under each sensory modality, by walking or verbal report, respectively. It can be observed that participants’ distance judgement under the visual and audiovisual conditions were generally accurate, while larger response deviations were observed in the auditory condition and at further distances for the DSL group. The following analysis will first focus on walking response, due to its ecological relevance to actual navigation.

Fig. 3.

Mean response distance as a function of actual presented distance across groups and conditions. Top row: control group. Middle row: VL group. Bottom row: DSL group. Left column: auditory condition. Center column: visual condition. Right column: audiovisual condition. Dark squares represent walking response, and gray circles represent verbal response.

Figure 4A summarizes the RMSE of the walking condition with each sensory modality. Because we observed no significant effect of lighting (F = 0.63, p = 0.425), data from both lighting conditions were combined. Age is a significant covariate (F = 13.94, p = 0.023), and all main effects and interactions reported below have adjusted for age. Significant main effects were observed for group (F = 26.56, p < 0.001), response type (F = 97.47, p < 0.001), and cue modality (F = 143.25, p < 0.001), as well as a significant interaction between response type and group (F = 12.57, p < 0.001). Since five participants in the DSL group used hearing aids during testing, we repeated the analyses excluding them. The overall pattern of results remained unchanged.

Fig. 4.

Distance estimation using walking responses. A. Root mean squared error (RMSE) of distance estimates across Control (gray bars and circles), vision loss (VL, cyan bars and squares), and dual sensory loss (DSL, orange bars and triangles) groups in auditory (A, left panel), visual (V, center panel), and audiovisual (AV, right panel) cue modalities. B. Slopes of the linear regression of response distance as a function of presented distance across groups and cue modalities. Error bars indicate standard error of the mean. Asterisks indicate statistically significant differences (*, p < .05; **, p < 0.1; ***, p < 0.001).

For the visual condition, the control group has a mean RMSE of 0.49 m; and the VL and DSL group showed no significant difference from the control group. All three groups performed similarly in the auditory condition, with a mean RMSE of 1.21, 1.25, and 1.34 m for the control, VL, and DSL groups, respectively. In the audiovisual condition, small but significant defects were observed in the VL and DSL groups. The control group had small RMSE in the audiovisual condition, averaging 0.55 m. Both VL and DSL group showed significantly higher RMSE than the control group in the audiovisual condition (VL: 0.66 m, p = 0.003; DSL: 0.69 m, p = 0.015). Moreover, when comparing the audiovisual condition with the single sensory conditions, we found that for both the VL or DSL groups the availability of simultaneous visual and auditory information did not improve the distance judgement but showed larger error than their better sense (i.e. vision alone, ps < 0.001).

The same results were confirmed when we repeated our analysis on the regression slopes between the walked distance and actual distance, summarized in Fig. 4B. In the visual condition, all three groups showed slopes close to 1, demonstrating excellent visual distance judgement even with impaired vision. In the auditory condition, the control group had an average slope of 0.43, suggesting a severe compression of the perceived auditory distances even for those with normal hearing. The DSL group exhibited significantly lower slopes than both the Control (p = 0.001) and VL (p = 0.003) groups, demonstrating further compression of perceived auditory distances with hearing loss. In the audiovisual condition, both VL (0.81, p = 0.014) and DSL (0.79, p = 0.042) groups had significantly lower slopes than Controls (0.92), which was also lower than their single best sense (i.e., vision, p < 0.001).

Vision and hearing factors on distance judgement by walking response

Next, we examined the relationship between distance judgement and the vision and hearing parameters of our participants. The primary parameters of interest include binocular visual acuity, contrast sensitivity and binaural hearing threshold. Hearing thresholds were quantified in two ways: the four-frequency pure-tone average across 0.5, 1, 2, and 4 kHz (HT_PTA4), and the threshold at 1 kHz (HT_1kHz), given that the auditory stimuli in the current study was centered around 1 kHz. We also included measures of lateral asymmetry, including the interocular differences in visual acuity and contrast sensitivity, and interaural differences in hearing thresholds, as interocular and interaural lateral asymmetries were shown to affect visual and auditory spatial perception⁵. Table 1 provides a summary of all correlation results.

Table 1.

Correlation between RMSE and slope with sensory status variables across conditions (auditory, visual and audiovisual), for walking response.

	RMSE			Slope
	Auditory	Visual	Audiovisual	Auditory	Visual	Audiovisual
Binocular VA	0.07	0.31*	0.55*	− 0.08	− 0.66*	− 0.60*
Binocular CS	− 0.11	− 0.21	− 0.54*	− 0.11	0.47	0.67*
Binaural HT_PTA4	0.22	− 0.12	0.05	− 0.55*	− 0.33	− 0.23
Binaural HT_1kHz	0.09	− 0.21	0.03	− 0.81*	− 0.67	− 0.56
Asymmetry VA	− 0.02	0.04	− 0.15	0.05	0.20	0.06
Asymmetry CS	− 0.14	− 0.05	− 0.11	0.08	0.36	− 0.02
Asymmetry HT_PTA4	0.19	− 0.06	0.08	− 0.50*	− 0.08	− 0.26
Asymmetry HT_1kHZ	0.16	− 0.15	− 0.02	− 0.65*	− 0.06	− 0.25

Sensory status variables include binocular visual acuity (VA), binocular contrast sensitivity (CS), hearing threshold (HT_PTA4), hearing threshold (HT_1kHz) and asymmetries between left/right eye acuity, contrast sensitivity, and hearing thresholds.

*Significant values (p < 0.05) are in [bold].

In the auditory condition, RMSE was not significantly correlated with any hearing parameters. Poorer binaural hearing thresholds were related to smaller slopes, indicating greater compression of perceived distances. This relationship was observed for both the standard four-frequency PTA measure (HT_PTA4: r =  − 0.55) and the 1 kHz hearing threshold (HT_1kHz: r =  − 0.81), with the association being stronger for the 1 kHz threshold. Similarly, greater interaural asymmetry in hearing thresholds was associated with smaller auditory slopes for both HT_PTA4 asymmetry (r =  − 0.50) and HT_1kHz asymmetry (r =  − 0.65). Consistent with the group comparisons in the previous section, the regression slope appears to be a more sensitive measure of hearing loss-induced localization issues than RMSE.

Can verbal report serve as proxy for walking response?

Lastly, we examined the relation between verbal and walking responses. We found that the relationship between walked distances and verbally reported distances varied across sensory conditions and groups.

Across all groups and conditions, verbal reports consistently showed larger RMSE than walking responses (p < 0.001), indicating that walking responses were more accurate overall. Moreover, there was a significant interaction effect between response type and group (p < 0.001), with the impacts of sensory loss being more pronounced on verbal report than walking. For example, in the vision-only condition, the VL and DSL groups showed similar RMSE with the Control group with walking responses, while both groups (VL: 1.06 m, DSL: 1.22 m) showed significantly larger RMSE than the Control group with verbal report (0.57 m, ps < 0.01).

We used the correlation of determination (r²) as an indicator of the agreement between walking and verbal reports (Fig. 5). In the visual conditions, the two response types were in great agreement, with r² values ranging from 0.81 to 0.96 across groups. In contrast, agreement in the auditory condition was much lower in all groups, ranging from 0.37 in the control group to 0.2 in the DSL group. In the audiovisual condition, controls again showed strong agreement between response types (r² = 0.92) similar to the visual condition, while VL and DSL groups demonstrated reduced agreement (r² = 0.62 and 0.72, respectively) than the visual condition.

Fig. 5.

Coefficient of determination values between verbal report to walked distances. Left, center, and right panels represent auditory, visual, and audiovisual conditions, respectively. The black circles, cyan squares, and orange triangles represent control, VL, and DSL groups, respectively. Higher values indicate stronger correspondence between verbal and walking responses.

In the visual and audiovisual conditions, localization RMSE and slope both showed strong correlations with visual status. Better binocular visual acuity was significantly associated with smaller errors and slope biases in both the visual (r = 0.31, p = 0.031; r =  − 0.65, p = 0.013) and audiovisual (r = 0.55, p < 0.001; r = 0.59, p < 0.001) conditions. Better binocular contrast sensitivity was also associated with smaller errors and slope biases in the audiovisual condition (r =  − 0.54, p < 0.001; r = 0.67, p = 0.003). Interocular acuity or contrast sensitivity asymmetry was not a significant predictor for visual or audiovisual distance judgement performance.

Discussion

The study evaluated the visual, auditory, and audiovisual distance judgement in individuals with vision and/or hearing loss in a simple localization task. We found that while the localization errors increased slightly as visual acuity and contrast sensitivity worsened, the visual distance judgement remained overall accurate in our sample of low vision participants. This finding is consistent with previous research that vision loss affects spatial tasks such as direction judgement and spatial updating, but the impact is overall small^16,30.

Under low lighting condition (~ 10 lx), the visual environmental information was minimized but the target was still salient (flashing red lights). When visibility is ensured, low vision individuals were able to preserve distance perception, indicating that they may be primarily relying on the relative height and linear perspectives for this visual task, rather than other environmental cues such as floor wall boundaries used in other studies in past literature^32,33. A more effective modification might be to reduce the saliency of the visual target, by reducing its contrast, or increasing the clutterness of the environment.

In contrast, the auditory cues used in our study produced much larger errors than vision across all groups including controls, suggesting that sound alone is not a reliable source for distance estimation in this task. The poor sound localization performance is unlikely due to the reverberations in our mobility room alone. While our testing environment was not an anechoic chamber, the reverberation of our environment was mild with an estimated reverberation time below 0.4 s for our testing stimuli. Previous sound localization research using virtual sound with 0.7 s reverberation time found no significant impact of localization performance of speech, music, and noise, when comparing to a no reverberation baseline³⁴.

The DSL group exhibited increased bias in the auditory condition, suggesting that when only auditory information is available, participants with hearing loss may have increasing difficulty distinguishing the relative strength of sounds at different distances to provide accurate distance estimation. Our sound stimuli centered on 1 kHz and showed stronger association with the listeners’ hearing threshold around 1 kHz than the standard pure tone average threshold. This strong relation supports that sound intensity might be a prominent cue used in our task. Broader band sound will likely be associated with hearing threshold across a broader frequency range.

Importantly, in the audiovisual condition, the availability of both visual and auditory cues did not reduce the localization errors but instead resulted in greater errors in the VL and DSL groups compared to their better sense (i.e., vision alone). This indicates a failure to integrate visual and auditory cues in an optimal fashion, as would be predicted by models of statistically optimal multisensory integration³⁵. One possible explanation is that individuals with vision loss increase their reliance on auditory signals², but auditory distance perception is not sufficiently reliable to effectively complement visual cues in these distance estimation tasks as shown by our data. Other possible explanations include inefficient audiovisual integration or conflict between visual and auditory information in the sensory-impaired groups. Future studies using explicit cue-conflict or cue-weighting paradigms are needed to clarify the underlying mechanism.

Indeed, individuals with visual loss increase their reliance on auditory cues for navigation; in some cases they even develop extraordinary echolocation skills (i.e., using self-generated or external echoes to localize objects)³⁶. Our findings raise the importance of capturing to what extent this compensation is valid, especially when vision loss is partial or co-occurs with hearing loss. Our present data indicate that, for participants with vision and hearing loss, degraded auditory information may not always be a reliable substitute for vision during distance estimation and may even serve as a distractor. However, evidence also suggested that perceptual learning can improve auditory spatial localization³⁷, and echolocation abilities can be trained even in sighted individuals³⁸. Moving forward, it will be critical to explore whether targeted multimodal (audio-visual) rehabilitative training can improve auditory localization and the integration of residual vision and hearing to improve overall spatial orientation skills, particularly in those with combined vision and hearing loss.

Our results showed verbal report is a valid proxy for actual walked distances in visual tasks as indicated by the high degree of agreements across groups (r² up to 0.96). This has practical implications for clinical and rehabilitation settings in assessing visually guided distance judgement when direct walking tasks may not always be feasible. However, under auditory-only conditions, the correspondence between verbal and walked estimates were variable and less reliable, especially among sensory-impaired participants. Under the audiovisual condition, while verbal report remains consistent with walking for control participants, this agreement decreased in sensory-impaired individuals, making it a less-than-ideal proxy for actual walking in clinical assessment.

Our DSL group was on average older than the other groups, which could contribute to increased error independent of sensory status. This age effect was particularly evident in the auditory-only condition, where age was a significant factor, with older individuals showing higher RMSE error and more distance compression as shown in the slope analysis. Even normal aging could lead to biases in space perception, which was also found in our previous study in direction judgement³⁹ and other studies in spatial references⁴⁰.

We would like to acknowledge the limitation in the generalizability of our findings. Our simple visual and auditory stimuli do not capture the full range of navigational challenges and obstacles faced in daily life. Further, we did not systematically manipulate the visual and auditory distance cues in our study to quantify their independent impact. The central goal of our study was to compare the relative performance of vision and hearing in judging distance, and to explore the patterns of integration between these senses. We note that the relative precision of visual and auditory distance judgement is unique to the combinations of vision and auditory targets⁴¹, the visual and acoustic environments, as well as the visual and auditory status of an individual⁴². Any single study with specific configuration will possibly lack generalizability to other testing conditions. We would also like to point out that the existence of suboptimal integration between the two sensory modalities in our DSL and VL groups is a major innovative finding from our study. The existence of such suboptimal integration will likely be replicable more broadly in other testing conditions. Future work should evaluate distance judgment in naturalistic environments, including target objects with different visual and auditory characteristics, moving obstacles, and variable spatial layouts. A design isolating the various visual and auditory cues will also provide more insights into the relative robustness of these cues to sensory loss.

We tested our participants with their habitual hearing aids, if any. We did not collect data on the type, functions, and duration of use of these devices, nor did we repeat the testing with and without these devices. Traditional hearing aids were found to have negative impact on sound localization⁴³ due to sound compression and were reported by users to be not helpful for sound localization³⁸. Built on our current study, it would be helpful to evaluate how state-of-the-art hearing devices can assist sound localization as well as facilitate sensory integration⁴⁴.

There are several other limitations to the present study. We did not include a group with isolated hearing impairment alone; future research should address this gap to better dissolve the specific contributions of hearing loss. Our sample is heterogeneous, reflecting the large variability in the cause and pathologies in the population with sensory loss. Larger and more balanced sample sizes will help identify more distinct distance judgement patterns between those with central versus peripheral field loss, and bilateral versus unilateral hearing loss.

In conclusion, our findings highlighted the overall robust visual distance judgement, even in those with vision loss. Under the simplified visual and auditory stimulus conditions used in this study, auditory distance judgement based on loudness appeared to be less precise than visual distance judgement based on height and linear perspective, particularly among participants with hearing loss. For individuals with vision and hearing loss, the access to both visual and auditory input may lead to poorer distance judgement than using vision alone, highlighting the importance of individualized strategy in optimizing the integration of vision and hearing. Verbal reports could be a practical and valid proxy for actual walking distance when visual information is the sole source for distance judgement, but clinicians should refrain from using verbal reports when the distance judgment involves localization of sound. Ongoing efforts aimed at enhancing multisensory rehabilitation and real-world spatial navigation will be important for improving independence and safety in individuals with sensory loss.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

RJ: Formal Analysis, Validation, Writing—Original draft. DB: Conceptualization, Methodology, Investigation. JPN: Conceptualization, Methodology, Writing—Edit. DCF: Conceptualization, Methodology, Writing—Edit. YX: Conceptualization, Methodology, Formal Analysis, Writing—Original draft.

Data availability

All relevant data are available from the corresponding author upon request.

Declarations

Competing interests

The authors declare no competing interests.