Wearable interfaces for orientation and wayfinding

People with severe visual impairment need a means of remaining oriented to their environment as they move through it. Three wearable orientation interfaces were developed and evaluated toward this purpose: a stereophonic sonic guide (sonic “carrot”), speech output, and shoulder-tapping system. Street crossing was used as a critical test setting in which to evaluate these interfaces. The shoulder-tapping system was found most universally usable. Considering the great variety of co-morbidities within this population, the authors concluded that a combined tapping/speech interface would provide usability and flexibility to the greatest number of people under the widest range of environmental conditions

A Note on the Different Interpretation of the Correlation Parameters in the Bivariate Probit and the Recursive Bivariate Probit

This note makes the point that, if a Bivariate Probit (BP) model is estimated on data arising from a Recursive Bivariate Probit (RBP) process, the resulting BP correlation parameter is a weighted average of the RBP correlation parameter and the parameter associated to the endogenous binary variable. Two corollaries follow this proposition: i) a zero correlation parameter in a BP model, usually interpreted as evidence of independence between the binary variables under study, may actually mask the presence of a RBP process; and ii) the interpretation of the correlation parameter in the RBP is not the same as in the BP -- i.e. the RBP correlation parameter does not necessarily reflect the correlation between the binary variables under study