Abstract
Bipedal gait is one of the most fundamental human behaviours, with the visual system guiding our movements through the environment that we are in. Our visual system is thought to have evolved to detect signals necessary for survival, whilst reducing noise, in the environmental niche of our past. Yet, the visual information of the built environments we live in today diverges substantially from those in which we evolved, with visual information necessary for survival in nature often prevalent as decorative background patterns in modern design. This raises the principle question of this thesis, namely, how well our visual system is able to guide our movements through modern built environments. To answer this question, three assumptions were tested:First, if well-adapted to a modern environment, visual prediction errors about the state of this environment should be minimal. Therefore, gait should not be affected by task-irrelevant visual information, such as regular and repetitive decorative floor patterns, even when the visual input does not match that of the physical world. Three different experiments revealed that high-contrast illusory depth patterns negatively impacted people’s subjective walking experience, and led to adjustments in stepping locations that adhere with the illusory information of the floors. This provided first evidence that the visual system is susceptible to prediction errors about the state of the environment, derived from design choices, to successfully guide gait.
Second, there should be no gait adaptation or entrainment to task-irrelevant visuo-spatial information of decorative floor patterns of otherwise flat, hazard-free floors. The results here revealed small but reliable differences in gait measures when walking over such patterns, indicating again that the gait cycle is not completely immune to changes of visuospatial decorative information on the ground plane.
Third, gait should not be negatively affected by task-irrelevant pattern noise, even if such noise were to produce aversive reactions, such as visual discomfort. Converging evidence from five experiments, however, revealed that certain spatial frequencies, contrast, and luminance of floor patterns negatively impacted gait, in line with predictions of changes in signal-to-noise ratio between task-relevant signals for walking and task-irrelevant background noise.
Collectively, these results indicate that decorative, task-irrelevant floor patterns have the capacity to introduce noise into the visual system when walking, resulting in more cautious gait behaviour.
This work is a first, yet fundamental, step toward understanding how low-level, task-irrelevant, visual patterns prevalent in our built environment, impacts gait in a way that might increase fall risk in vulnerable groups within our society. Findings emphasise that the way we design our environments needs to account for the way in which our visual system guides our movements, ultimately affecting population health and wellbeing.
| Date of Award | 3 Oct 2023 |
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| Original language | English |
| Awarding Institution |
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| Sponsors | Engineering and Physical Sciences Research Council |
| Supervisor | Ute B Leonards (Supervisor) |