Thursday, April 16, 2009

Veering? What veering? (and a new article)

I am posting these excerpts from Guth’s chapter as a reminder of the theoretical and experimental underpinnings of at least one of the variables we are dealing with in the WiiCane project:

Once the veering tendency of each of these individuals had been well documented, he or she participated in a series of about fifteen 20-trial training sessions. The training procedure was modeled after bandwidth feedback approaches used in athletic training (Schmidt, 1991). During each training trial, a participant started with his or her back to a portable wall, walked away from the wall, and attempted to stay within a 2-m wide, 20-m long simulated crosswalk defined by two parallel, ankle-level infrared beams. Whenever either beam was broken, the participant immediately heard—through earphones—
the direction of the error and the distance that had been traveled before veering out of the “crosswalk.” (p. 356)
All participants exhibited marked improvement over the course of this training and, as illustrated in Figure 18–1, the effects were still evident 5 months after the cessation of training. (p. 356).
While one participant reported a cognitive strategy that wasn’t consistently effective (i.e., “step to the left every few steps”), the others reported that they simply “learned what it felt like to walk straight.” (p. 357)
Our feedback system was unlike anything experienced during the everyday travel of blind pedestrians. It required that well-aligned participants attempt to generate a straight line path and stopped them when they had deviated 1 m to either side of the intended path. (p. 358)
Although blind pedestrians have many opportunities to experience straight-line walking, this experience occurs in the presence of continuous guidance. (p 358)
One of the surprising aspects of our training study was that the effects lasted for at least 5 months, the point at which we ceased taking follow-up data. (p. 359)
The training study revealed that practice with feedback is useful, but it remains unclear what elements of locomotion were modified during training. (p. 359)

Also, you may want to check out this other journal article:

Kallie, C. S., Schrater, P. R., & Legge, G. E. (2007). Variability in stepping direction explains the veering behavior of blind walkers. Journal of Experimental Psychology: Human Perception and Performance, 33(1), 183-200.

I cannot attach it here but will email the article to stakeholders.

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