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Shaziela Ishak, Adam Assoian, Joseph Lehan; Visual Guidance When Army Crawling Under Barriers. Journal of Vision 2013;13(9):477. doi: https://doi.org/10.1167/13.9.477.
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© ARVO (1962-2015); The Authors (2016-present)
Despite its everyday relevance, few studies have examined how our visual perception is affected when objects are attached to the body. Successfully fitting through openings with objects involves visual guidance of movement. For adaptive motor control, we must recognize prospectively that actions such as wearing a bulky coat, holding a computer, or moving furniture changes which openings we can fit through. Inaccurate decisions can lead to injury or property damage. We assessed adults’ perception of affordances for army crawling (stomach touching the ground) in a person-plus-object system. Participants were presented with randomly ordered overhead barriers of different heights (10 to 70cm). Barriers were 15, 20, 25, 30, or 35cm larger than participant’s sagittal body width. For each trial participants army crawled under a barrier then, choose a backpack (10, 15, 20, 25, or 30cm thick) to wear, and finally crawled back under the barrier wearing the backpack. Participants were asked to pick the largest backpack they thought they could wear to army crawl without touching barriers. Videos revealed that participants rarely looked at barriers as they crawled under them without backpacks. Nonetheless, participants found another source of visual information. Almost every participant looked back and forth between backpacks and barriers for every trial when choosing a backpack. Participants reported combining proprioceptive and visual information about backpack and barrier heights in their decisions. Most adults displayed conservative response criteria: picking backpacks a level smaller than the barrier. For the +25-cm barrier 50% choose the15-cm bag but for +30-cm barrier 50% choose the 20-cm bag. This pattern led 42% of participants to refuse backpacks for the smallest barriers. Participants did not always leave of safety margin, 83% of participants hit different barriers at least once. Findings are discussed in terms of combining visual and proprioceptive information to make adaptive decisions.
Meeting abstract presented at VSS 2013
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