Fig 1.
Experimental Setups for ME and TE.
Picture depicts the research personnel tracking the curves presented on the surface of the rotating wheel (on the left picture) and on the touchscreen monitor (on the right picture).
Fig 2.
For different experimental conditions the sequence of the curves are changed in order to prevent subjects from memorizing the order. The curve path is printed on a paper and wrapped around the rotating disc. Curves are given in the same aspect ratio as they are seen on the rotating wheel. This figure is 1:2 reduced in dimension to fit the margins. As the wheel rotates clockwise, curves flow from right to left. Each curve is designed such that tracking the curve with the index finger imitates reading of a short Braille sentence. The parts of the curve with arrows pointing left mimic reversals observed during Braille reading. Subjects start tracking with the first curve (marked with red circle), and proceed with the next one. After completing seven distinct curves, they repeat tracking the same path. The red arrow at curve 7 guides the subject to proceed to curve 1, to repeat the path.
Fig 3.
For each condition the sequence of the curves are changed in order to prevent the subject from memorizing the order. The curve path repeats itself with the same sequence until the subject completes tracking within the given time. Curves are given in the same aspect ratio as they are seen on the touch monitor. This figure is 1:4 reduced in dimension to fit the margins. Curves flow from right to left. As in ME, each curve is designed such that tracking the curve with the index finger imitates reading of a short Braille sentence. The parts of the curve that point to left mimic reversals in Braille reading.
Fig 4.
Evaluation of subjects’ performance in TE.
Figure represents a sample curve and a trace path generated by the researcher. The actual points of the curve are colored blue whereas the generated trace path/points are seen in green. In order to evaluate subjects’ performance in TE, two metrics are studied: the accuracy and the percentage of the tasks accomplished within given time. Using a nearest point search algorithm, the closest points on the actual curve for each point in the subject’s trace path are found. The sample in the figure shows the distances between those closest points and the tracked path colored in red. A good performance is represented in the first upper half of the curve where the distance between the closest points and user points are relatively shorter indicating that the user was able to track the path as close to the actual path as possible.
Table 1.
Performance in ME and Reversal Completion Rate in TE.
Fig 5.
Mean workload metrics for different experimental conditions performed in ME.
Results are based on NASA–TLX. Error bars represent standard error. Mental demand scores in NAA and AA are found to be statistically significant at the 0.05 level while no statistical significance is observed for the remaining workloads.
Fig 6.
Median percentage of the curve path covered by the subjects for each experimental condition in TE.
Error bars represent the standard error. Different letters on error bars indicate statistical significance in pairwise comparisons performed with Bonferroni post-hoc tests.
Fig 7.
Mean lateral deviations from the horizontal parts of the curve paths in TE.
Mean values are geometric means calculated by antilog of transformed data. Different letters on bars indicate statistical significance in pairwise comparisons performed with Bonferroni post-hoc tests. See ‘Results’ section for confidence intervals.
Fig 8.
Average Mental Demand vs. Performance graph for TE based on NASA–TLX.
Performance of subjects in TE experiments based on curve coverage versus mental demand as measured by NASA–TLX, where error bars represent the standard error. See Fig 6 for significance of this performance metric.
Fig 9.
Mean workload metrics for different experimental conditions performed in TE.
Results are based on NASA–TLX. Error bars represent standard error. Different letters on bars indicate statistical significance in pairwise comparisons performed with Bonferroni post-hoc tests. Letters shared in common between experimental conditions indicate no significant difference.
Fig 10.
Experimental setup used in the human subject testing with blind individuals.
Setup components marked on the picture are explained on the right hand side with matching letters.
Fig 11.
Braille reading accuracy in different experimental conditions.
Percentages shown in the figure are calculated by dividing the number of accurately read words by the total number of words in each experimental condition. Accurate reading is assessed based on subject’s reading out loud.