Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Kinesiology

Program Name/Specialization

<--Please Select Program Name/Specialization-->

Faculty/School

Faculty of Science

First Advisor

Michael Cinelli

Advisor Role

Associate Professor

Abstract

Aperture crossing tasks are commonly used to test an individual’s perception-action integration capabilities. Multiple studies have demonstrated that young adults use body-scaled information to guide behaviours while completing a static aperture task (Franchak & Adolph, 2014; Hackney et al., 2014; Hackney & Cinelli, 2013; Warren & Whang, 1987). However, it remains unclear as to what visual information young adults are using to determine the passability of an aperture. One theory proposed by Fajen (2013), is that young adults use a ratio of their eye height (EH) to shoulder width (SW). To test this theory, eye height manipulation studies have asked participants to make perceptual judgments, which may not reflect actions or had them walk on blocks, which altered their biomechanics. Therefore, the purpose of the thesis was to determine if eye height information is used to inform a person about their body size and is utilized as the driving information source which dictates actions. It was hypothesized that an increase/decrease in eye height would lead to participants’ self-perception of shoulder width (i.e., body size) being larger or smaller respectively and give themselves more or less space to pass through safely when compared to the no manipulation condition. Collision avoidance behaviours were used to determine if a change in perception of body size occurred in two different virtual environmental tasks, those being a static aperture crossing task (Study 1) and a closing gap task (Study 2). Participants across both studies experienced the same three eye height conditions/manipulations, Normal (no EH manipulation), Tall (+30cm to EH), and Small (-30cm to EH). Eye height manipulations occurred in the VE by having the headset view of the VE increase/decrease in virtual eye height based on each participant’s normal eye height without necessarily changing gait biomechanics. Study 1; Fifteen young adults (9 male, 22.3 +/- 1.5) walked along a 7.5m long pathway in virtual reality (VR), towards a goal with an aperture created out of two vertical poles (20cm in diameter) located along the path 5m from the start. The objective of the participants was to reach the goal either by passing through or around stationary poles without rotating their shoulders or colliding with one of the 9-block randomized aperture sizes (ranging from 0.8-1.8x SW). Using head position of the participant, head position at the time of crossing (M-L), critical point, and deviation onset (A-P) were calculated. Study 2; Sixteen young adult participants (10 males; 22.2 +/- 1.6 years) walked along a 7.5m long pathway in virtual reality (VR), towards a goal with a closing doorway (initially opened to 4m wide) located along the path 3.5m from the start. The objective of the participants was to reach the goal square without rotating their shoulders or speeding up to pass through one of 9 door closing speeds relating to each participant's average walking speed (0.6, 0.7, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0, 1.2x walking speed). Using head position of the participant, average slow down distance from the doors, and 50% switch point were calculated. Results from both studies revealed that what information source a young adult is utilizing, will depend on the task. The results from study 1 revealed that young adults are utilizing information from their eye height to inform them about their body size while completing a static aperture task. When young adults were in the Tall condition, their self-perception of body size was wider. While the opposite was true for the Small condition, where young adults' collision avoidance behaviours shifted to acting narrower. Interestingly, study 2 did not have the same results, as young adults were not utilizing eye height information when completing the closing gap task. Instead, young adults were utilizing optical variables such as beta angle as the primary information source to determine passability. The results revealed that while completing a static task that relies on body scaled information, eye height information is utilized to inform about body size to drive actions. While during a closing gap task that relies on action-scaled information, body size is disregarded, and optical information such as beta angle is utilized to determine passability.

Convocation Year

2025

Convocation Season

Fall

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Available for download on Sunday, June 18, 2028

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Motor Control Commons

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