Using a list of potential blind subjects provided by two O&M instructors in San Francisco, telephone contact was made and it was explained that subjects needed to be legally blind and be able to get to the test area themselves (the principal researcher has a vision impairment and could not offer to pick up subjects with a car). Subjects were offered $50 each for their time and effort. If interested, they were immediately assigned to one of the two test order conditions in an alternating fashion. At that time, a phone interview was conducted on the pre-test questionnaire or an appointment was made to interview them later. The phone interview took about 30-45 minutes. At the end of the phone interview, a field test was scheduled and arrangements were made to meet them near the test site. Subjects were asked to meet the experimenter away from the Caltrain test area, either at a bus stop, cab stand, or at the Light Rail station, all of which were nearby. After the field test, subjects were taken away from the test area and offered a drink and a place to sit while the post-test interviews were given and recorded. Subjects were then paid, signed a receipt, and were escorted to their requested mode of transportation for their return trip. Thirty subjects were recruited and they all completed the entire experiment.
Table 1. 2 Distribution of Subject Characteristics across the 2 Conditions
|
Subject Characteristics |
Condition 1 |
Condition 2 |
|
Regular Method |
With RIAS |
|
|
NRIAS 1st |
RIAS 1st |
|
|
Gender ratio |
60% M |
67% M |
|
Age |
34 |
39 |
|
Congenitally (born) blind |
10 |
7 |
|
Age at onset of blindness (non- congenital) |
18.8 |
18.1 |
|
Education completed (median) |
Some Col. |
Some Col. |
|
Years legally blind |
28.2 |
29.3 |
|
Subjects, no useful vision |
11 |
9 |
|
Subjects, see some shape |
2 |
4 |
|
Subjects, see some objects |
2 |
2 |
|
Independent travel (mobility rating) |
1.9 |
1.7 |
|
General sense of direction (mobility rating) |
2.4 |
1.9 |
|
Mobility in new environment (rating) |
2.9 |
2.7 |
|
Frequency of learning a new route (rating) |
3.7 |
3.7 |
|
Familiarity with Talking Signs® (rating) |
1.8 |
1.5 |
|
Familiarity with Caltrain station (rating) |
1.5 |
1.9 |
All subjects received about 10 to 15 minutes of training using Talking Signs®. An explanation was given as to how the transmitter sends a conical beam of light that carries a message that the receiver picks up and speaks to the user (see Section 2.4 for details). They practiced finding the edges of the transmitted cone by moving the receiver and finding where the message finally disappeared at the top, bottom, and both side edges of the cone. A transmitter that was not on the route was used for this purpose, and subjects practiced walking and following the beam to this site three times. Next, each person was taken to another location not on the route and practiced walking toward this transmitter. A portable transmitter was then attached to a light pole away from the route, and they made three more walks to locate the pole. These last two transmitters were close enough that subjects could receive signals from both while standing at a central location. Here they learned how to orient themselves between two signals. The initial explanation and these nine practice walks were the only training each received. Other experiments using non-directional acoustical sounds have required many weeks or months of training to teach auditory localization (Easton & Bentzen, 1999) .
The major purpose of the experiment was to document how people with vision impairments performed tasks with their regular method and when using location-based infrared transmitted auditory signage. However, some data were obtained from sighted subjects to use as a baseline comparison. Clark-Carter et al. (1986) suggests that the best way to test different navigation aids is to compare walking times. By extension, the walk times of the blind subjects are compared with that of a sighted person to better compare the degree of restriction imposed by the absence of vision. The field experiment at the Caltrain station was based on tasks requiring searching and walking. Baseline walk times were obtained from two sighted subjects. The first subject was a research assistant who had never been to the test site before. He was blindfolded and taken to the start point. Here, the blindfold was removed, and he performed the field tasks. Walk times, requests for help, and errors were recorded. Since it was his first exposure to the environment, several errors were made, as was expected. His times represented a first-time sighted user (FTSU). To obtain a baseline of error-free walk times, the principal researcher, who was very familiar with the environment, walked the route. His times represented a familiar sighted user (FSU). The FTSU was younger and taller and his walk times were often a few seconds faster than the FSU, but since he was unfamiliar with the area, he did not always walk a direct path and a few times were much longer, so that the total time for the FSU were less than for the FTSU. APPENDIX 1 shows the times for these two sighted users.
The effect of vision loss on transfer making behavior was studied by asking a series of questions about perceived behavior when making a decision to transfer. In order to compare those responses, 30 sighted people were interviewed. On the daily public transit ride to and from the experiment site, the principal investigator looked for sighted people of the same sex and general age range as that day’s test subjects, who were then asked if they were regular users of transit, and, if so, were told of the experiment. They were asked the same six questions that were asked of the blind test subjects about transfer making behavior. This group represented sighted users (SU).
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