Exploring the relationship between preferred bubble tube speeds in sensory rooms and physiological–psychological factors: A study on interoceptive sensitivity, subjective time perception, visual discomfort levels, and anxiety levels

Introduction

Sensory overload is a common experience in individuals with sensory hypersensitivity, in which everyday stimuli such as light (Lucker, 2013), noise (Khalfa et al., 2004; Landon et al., 2016), and touch (Blakemore et al., 2006) become overwhelming. They may find it challenging to navigate routine environments (Lucker, 2013), thus affecting their ability to function effectively in daily life (Kim et al., 2000). Researchers and practitioners have developed various methods and tools to address these problems (Koegel et al., 2004). These approaches aim not only to reduce stress caused by sensory overload (Mazurek et al., 2013) but also to improve individuals’ quality of life and functional abilities (Hannant et al., 2016). Studies have shown that sensory hypersensitivity can significantly influence behavior and emotions and is correlated with psychiatric symptoms (Engel-Yeger et al., 2016).

Designed to provide a controlled environment that aids in self-regulation and relaxation, sensory rooms are typically equipped with assistive technologies and specialized elements. A prime example of such a space is the Snoezelen room, a multi-sensory environment developed in the Netherlands in the 1970s (Hulsegge & Verheul, 2005). Snoezelen rooms combine sensory experiences to create a soothing atmosphere where users can explore various stimuli at their own pace, thereby promoting relaxation and reducing stress (Hulsegge & Verheul, 2005). These environments are particularly beneficial in psychiatric inpatient care where they help individuals manage sensory overload and regulate distress. Research has shown that sensory rooms, including Snoezelen rooms, significantly reduce distress and aid emotional regulation, especially in individuals with a history of aggression or anxiety disorders (Haig & Hallett, 2023; West et al., 2017). They serve as valuable tools for self-management and offer alternatives to more restrictive psychiatric care practices (Barbic et al., 2019). In forensic mental health settings, these rooms have been found to reduce patient stress, support recovery, and enhance the overall patient experience within a facility (Wiglesworth & Farnworth, 2016).

Among the various types of sensory equipment used in these rooms, bubble tubes usually serve as a central element, offering visual, tactile, and auditory stimulation. They are tall, clear cylinders filled with water in which bubbles rise continuously owing to an internal air pump, often accompanied by color-changing LED lights. These tubes are designed to create a calming effect while engaging users visually and tactilely, making them beneficial for individuals with sensory processing disorders, including autism spectrum disorders (ASDs). The continuous movement and changing colors of the bubbles facilitate visual tracking, color recognition, and tactile feedback, which can soothe and attract attention (Fujisawa, 2021). Unwin et al. (2024) investigated how children with autism use different types of sensory equipment in multi-sensory environments and revealed that bubble tubes are among the most popular.

However, the precise mechanisms by which the bubble tubes induce relaxation remain poorly understood. Although their calming effects are well-documented, the specific factors contributing to these outcomes remain uncertain. It is likely that a combination of sensory stimuli, such as the visual rhythm of the bubbles, changing colors, and gentle auditory stimuli, work in concert to engage multiple senses and promote relaxation. Nonetheless, individual responses to bubble tubes can vary significantly, suggesting that personal factors play a crucial role in shaping the overall experience. As a means of moving closer to elucidating these mechanisms, we explored the physiological and psychological factors that contribute to individual differences in how the effects of bubble tubes are experienced.

To comprehensively understand the determinants of the preferred speed for the bubbles in bubble tubes, we investigated several key physiological and psychological factors: interoceptive sensitivity, subjective time perception, visual discomfort, and anxiety. Each of these variables plays a crucial role in shaping the user’s sensory experience and response to stimuli. Because the underlying mechanism may be complex, we began our investigation by examining the correlations between preferred bubble tube speeds and the aforementioned factors. This approach allowed us to determine whether interoceptive sensitivity, perception of the internal clock, visual discomfort levels, and anxiety were at least partially involved in generating comfort and relaxation. By examining these factors and their correlations, we aimed to elucidate the complex interplay between physiological and psychological states and the effectiveness of sensory interventions. If significant correlations exist, this will provide a foundation for further exploration of the causal relationships and mechanisms underlying preferred bubble tube speeds.

Interoceptive sensitivity, defined as the ability to perceive internal bodily sensations, is fundamental in regulating responses to external stimuli (Garfinkel & Critchley, 2013). Recent advances in this field suggest that individuals with high interoceptive accuracy who can keenly perceive internal states, such as heartbeat, are better equipped to manage their emotional responses to sensory stimuli (Tanaka et al., 2021). Pollatos et al. (2012) found that interoceptive sensitivity is associated with a heightened awareness of emotional and physiological states, which influences how individuals respond to environmental stimuli.

Our study examined subjective time perception, a critical facet of cognitive processing influenced by attention, emotion, and sensory input. Research indicates that an individual’s perception of time can significantly affect their mental health and behavioral responses (Yabe & Yamada, 2023). Given that bubble tubes are designed to enhance sensory processing and well-being, and considering the prevalence of various sensory processing disorders among users, it is highly pertinent to explore the relationship between users’ subjective time perception and their preferred bubble tube speeds.

Visual discomfort can also significantly affect the efficacy of bubble tubes. Research has shown that individuals with high levels of visual discomfort often perform visual tasks more slowly, suggesting that discomfort can significantly affect visual processing efficiency (Conlon & Humphreys, 2001). Researchers have also explored the neural basis of visual discomfort and have found that when processing uncomfortable stimuli, neural responses tend to be stronger and less frequent. This indicates inefficient neural coding, leading to increased sensory sensitivity and discomfort (Wilkins, 2016). These findings suggest that bubble tube speed settings should consider the potential for visual discomfort and its neural correlation. Therefore, visual discomfort is a crucial factor in the design of sensory rooms because bubble tube speed can either alleviate or exacerbate this discomfort. By understanding the relationship between users’ visual discomfort levels and their preferred bubble tube speeds, we can tailor the sensory environment to minimize sensory fatigue and enhance comfort.

Anxiety level is another important factor that should be considered as this can significantly affect how individuals interact with their environments. High levels of anxiety may heighten sensitivity to sensory stimuli, making the speed of bubble movement particularly crucial. Research indicates a strong link between anxiety and increased sensitivity to sensory stimuli. For instance, anxiety disorders are associated with heightened sensory processing, in which individuals exhibit increased sensitivity to specific environmental cues (Åhs et al., 2013). Furthermore, sensory processing sensitivity is correlated with higher levels of anxiety, depression, and stress. This relationship suggests that individuals who process sensory information more intensely experience greater psychological distress, particularly when mindfulness and acceptance levels are low (Bakker & Moulding, 2012). Assessing user anxiety levels can provide valuable insights into how bubble tubes can be optimized to reduce anxiety and provide a calming effect in sensory rooms.

By examining the correlation between users’ preferred bubble tube speeds and physiological–psychological factors, we can develop a comprehensive understanding of how these factors influence the sensory experience. Understanding these relationships will facilitate the development of effective therapeutic strategies. For instance, by tailoring sensory stimuli, such as adjusting the bubble movement speed to users’ specific anxiety levels, the calming effects of sensory rooms can be enhanced. This optimization approach allows for the creation of sensory environments that better meet the needs of individuals with sensory processing disorders, thereby enhancing comfort and engagement.

Methods

Stimuli

We used a Random Dot Motion (RDM) stimulus program developed using the Flutter SDK. The source code (v1.0) is available under the MIT License on Zenodo (Su, 2025c; https://doi.org/10.5281/zenodo.14795461), with a Windows executable build concurrently archived (Su, 2025d; https://doi.org/10.5281/zenodo.14795194). running on a Lenovo laptop (screen dimensions: 36.3 cm * 23.8 cm, resolution: 1920 * 1080, model number: 115423562). Our RDM program generated a certain number of dots per second that moved vertically upward within a circular area at the center of the screen ( Figure 1). All dots moved at the same speed, simulating the upward movement of the bubbles in the tube. This circular area had a diameter of 1000 pixels, which corresponds to a visual angle of 21.88 degrees. A white fixation cross was placed at the center of the circular area. This helped ensure that participants kept their gazes fixed on a specific location on the screen and their attention focused on the screen, making it easier for them to detect subsequent stimuli. In the experiment, the program was set to randomly generate 200 small dots per second within a circular area. Each dot had a radius of 12 pixels, corresponding to a visual angle of 0.26 degrees. All dots had the same brightness and chromaticity, set at 128 cd/m², X = 0.23, Y = 0.28 in the CIE 1931 color space, ensuring consistent visual stimuli in the CIE 1931 color space, ensuring consistent visual stimuli.

Figure 1. Schematics of the Random Dot Motion (RDM) stimulus.

During the experiment, participants adjusted the upward speed of the dots using a keyboard. The program recorded the current speed of the dots upon pressing the “Enter” key, allowing for review after the experiment. The upward movement speed of the dots ranged from 0 pixel/s (0 degrees per second) to a maximum of 1000 pixels/s (21.88 degrees per second). Bellini et al. (2023) stated that sensory environments typically use soft, dim lighting to create a tranquil atmosphere, helping to reduce anxiety and stress, and enhance comfort and relaxation, thereby positively impacting psychological and physiological health. Therefore, our experiment was conducted in a dark room designed to simulate an appropriate sensory environment ( Figure 2).

Figure 2. Experimental setup shows a participant adjusting the speed of the dots in the Random Dot Motion (RDM) stimulus.

Results

Discussion

This study aimed to investigate the relationship between various physiological and psychological factors and Average Preferred Speed (APS) during RDM stimulation. Using both Spearman’s correlation and multiple regression analyses, we identified several significant predictors of APS, providing valuable insights into the interplay between interoceptive sensitivity, subjective time perception, visual discomfort levels, anxiety levels, and the preferred speeds for bubble tubes.

The significant positive correlation between the absolute value of the Absolute Difference between Perceived and Actual Heart Rate (HRDiff ) and APS (rs = 0.49, 95% CI [.238, .681], p < .001) underscores the pivotal role of interoceptive sensitivity in shaping the preferred RDM stimulation speeds. Interoceptive sensitivity and sensory processing are related via a clear mechanistic pathway. Enhanced interoceptive sensitivity enables more precise detection of internal physiological states, which, in turn, facilitates higher temporal resolution in sensory processing. This heightened internal awareness allows individuals to detect subtle physiological responses to sensory stimuli more accurately. Recent research by Grist et al. (2023) supports this connection by demonstrating that interoceptive awareness is correlated with sensory processing capabilities in neurotypical children, suggesting this relationship is fundamental to human development.

The observed preference for slower RDM speeds among individuals with higher interoceptive sensitivity stems from two key mechanisms. First, reduced speed decreases information load and prevents sensory system overload. Second, slower presentation speeds provide extended processing windows, allowing for more thorough signal integration. This pathway enhances sensory comfort in two ways: by reducing sensory overload, and by improving processing precision. Slower information presentation lowers neural stress and fatigue, while better signal-to-noise ratios and prediction accuracy promote psychological ease. Together, these factors enable effortless engagement with the sensory environment, facilitating effective tracking and integration of stimuli for an optimal sensory experience.

The positive correlation between anxiety levels and APS (rs = 0.31, 95% CI [.076, .582] p = .028), as confirmed by the multiple regression analysis (β = 0.44, p = .001), suggests that faster RDM stimulation speeds may be particularly beneficial for individuals with higher anxiety levels. This finding is consistent with that of Park and Youn (2022) who found that high-intensity visual stimuli can replenish cognitive resources and reduce anxiety. Faster speeds may induce a state of physiological arousal that counteracts the heightened arousal associated with anxiety, thereby promoting relaxation and calmness.

The multiple regression analysis not only confirmed the independent contribution of anxiety levels to the APS, but also revealed the significant influence of subjective time perception. Although not significantly correlated with APS in the correlation analysis, the Absolute Difference between Estimated Time and Actual Time (TimeDiff ) emerged as a predictor in the regression model (β = 0.36, p = .007), suggesting that subjective time perception may interact with other factors to influence the preferred RDM stimulation speed in a complex manner. Individuals with lower subjective time-perception accuracy, in the same way as those with lower interoceptive sensitivity, may perceive faster RDM stimulation speeds as more comfortable. This finding suggests a potential link between time perception and interoceptive processing, as proposed by Di Lernia et al. (2018). It is possible that the perceived passage of time is influenced by internal bodily sensations and that individuals with heightened interoceptive awareness may experience time differently, leading them to perceive slower RDM speeds as more comfortable.

Furthermore, while visual discomfort levels did not show significant correlations with APS in the correlation analysis, the multiple regression analysis revealed some nuanced effects. Specifically, higher VDS-J scores were significantly negatively correlated with slower APS (β = -0.33, p = .019). These results indicate that although visual discomfort may not independently predict the APS, it contributes to the overall model of the preferred speed. This suggests that individuals with higher visual discomfort levels perceive slower speeds as more comfortable. This finding aligns with that of Penacchio et al. (2023) who suggested that slower visual stimulus speeds can alleviate discomfort in individuals with visual sensitivity. This emphasizes the importance of tailoring the sensory stimuli to individual comfort levels to maximize the therapeutic benefits of RDM stimulation.

These insights contribute to our understanding of the complex interplay between physiological and psychological factors in determining the preferred RDM stimulation speed and suggest potential pathways for designing sensory interventions. Our findings showed that participants’ preferred RDM stimulation speeds varied according to their physiological and psychological factors, underscoring the need for personalized design in bubble tubes and sensory rooms.

Conclusions

This study provides valuable insights into the complex interplay between the physiological and psychological factors that influence preferred RDM stimulation speeds. Our findings reveal that interoceptive sensitivity, subjective time perception, visual discomfort, and anxiety are significant predictors.

These results demonstrate that individuals with lower interoceptive sensitivity tend to prefer faster RDM stimulation speeds, possibly as a compensatory mechanism for reduced internal bodily awareness. This relationship between interoceptive sensitivity and the preferred speed underscores the importance of considering individual physiological differences in bubble tubes and sensory rooms.

Anxiety levels emerged as a significant factor, with participants’ anxiety levels significantly and positively correlated with the preferred RDM speed. This finding suggests that faster and more intense visual stimuli may have therapeutic applications for individuals with anxiety disorders. Saiu and Grosso (2022) demonstrated that combined audio-visual stimulation significantly reduced anxiety levels, systolic blood pressure, and heart rate in patients undergoing surgery, supporting the potential of multi-sensory interventions in anxiety management.

The subjective time perception ability was also related to the preferred RDM stimulation speed, with participants with lower accuracy in time perception tending to prefer faster speeds. Previous research has shown that interoceptive focus significantly influences subjective time perception, with heightened interoceptive awareness amplifying the time-dilating effects of fear and the time-accelerating effects of amusement (Pollatos et al., 2014). This, in turn, may have affected participants’ perceptions of comfort in response to RDM stimulation speeds.

Although the visual discomfort levels were not independently correlated with the preferred speed in our Spearman’s correlation analysis, they emerged as significant predictors in our multiple regression analysis. Specifically, participants with higher visual sensitivity tended to prefer slower speeds. This finding highlights the importance of designers considering individual levels of visual discomfort when designing visual stimuli in bubble tubes or sensory rooms and offering tailored sensory experiences that cater to each person’s diverse sensory needs.

As Ziegler (2015) noted in her research on multi-sensory design in healthcare settings, environments that allow users to customize sensory inputs contribute to stress reduction and improved well-being. Garzotto et al. (2019) developed extensible multilayer software and hardware platform to connect and manage different devices in a sensory room, thereby enabling therapists to fully customize activities in multi-sensory environments for different children. The findings of this study support the idea that tailored sensory environments, such as those incorporating adjustable bubble tube speeds, can enhance the therapeutic outcomes for individuals with varying sensory hypersensitivities and psychological states.

Building on our previous research (Su et al., 2024), which demonstrated that sensory-hypersensitive individuals have greater variations in their preferences for wallpaper colors and patterns, this study further underscores the necessity for customizable sensory rooms tailored to each person’s unique sensory needs.

Future research should explore the potential therapeutic applications of tailored bubble tube speed stimulation to reduce anxiety. It is also crucial to investigate the intrinsic relationships among variables such as interoceptive sensitivity, subjective time perception, anxiety levels, and visual discomfort. Additionally, conducting longitudinal studies to examine how participants’ preferred speeds change over time or with repeated exposure to the same visual stimuli would provide valuable insights.

In conclusion, this study enhances our understanding of the factors influencing preferred bubble tube speeds and lays the groundwork for the development of more personalized and effective sensory interventions to improve outcomes for individuals with diverse sensory needs.

Consent

Written informed consent for publication of the participants details was obtained from the participants.