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Interstroke Intervals
During Continuous Typing of Visually Impaired College Students
Focus: School Years
Topic: Access Technology
Hisayuki Ishida
Associate Professor
Research Center on Educational Media
Tsukuba College of Technology
4-12-7, Kasuga, Tsukuba-shi, Ibaraki,
305-0821, Japan
+81-298-58-9582
ishida@k.tsukuba-tech.ac.jp
Kazuhiko Amano
Research Associate
General Education for the Visually Impaired
Tsukuba College of Technology
4-12-7, Kasuga, Tsukuba-shi, Ibaraki,
305-0821, Japan
+81-298-58-9522
kazu@k.tsukuba-tech.ac.jp
Abstract
This study investigated interstroke intervals during the continuous typing of visually impaired college students. The subjects copytyped the tasks presented aurally and the intervals between two successive keytypings were measured after the experiments. Characteristics of finger movements from keys a, i, u, e, and o to other keys differed from those of inverse movements in point of interstroke intervals. Inverse movements indicated shorter intervals. Discussions were made about the way to speed up typing through improvement of finger movements toward special directions.
Introduction
Recently, personal computers are closely connected to the daily life of the sighted and the visually impaired people equally. Usually, in the Windows environment, a mouse is indispensable for an operation. However, it is difficult for the visually impaired people, especially for the blind, to point targets by the mouse. Therefore, they use a keyboard to input characters and numerical values.
On keyboarding, another words keypressing to input data toward computer programs, it is necessary for the users to be trained to operate the keyboard smoothly. In the training, it is included to learn the arrangement of the keyboard, how to set fingers, and how to move them toward correct directions.
We have researched the characteristics of keyboarding of the college students with visual impairment to clarify the effective operation methods to input kanji and kana characters. On the keyboarding of the visually impaired students, studies have been done chiefly in terms of the errors, for various kinds of restrictions such as the impossibility to show printed matter as tasks to the blind, have made it difficult for the visually impaired people to be measured on the speed of keyboarding.
The proceeding researches have revealed that in a discontinuous paradigm, the college students with visual impairment attending a beginning typing class made more substitution errors than that of omission or insertion. On the other hand, in a continuous typing paradigm, there are much more omission errors than the other two errors. This phenomenon is thought to be the compensation for obtaining maximum quantity of input data by thinning down the outputs.
As mentioned above, the study of typing speed on the blind people is considered to be difficult because the method of displaying tasks has not been established yet. On this consideration, one of the authors of this study displayed tasks aurally to the blind college students and measured the interstroke intervals to examine the relation between interstroke interval and direction of finger-movements. The results suggested that the characteristics of finger-movements from keys a, i, u, e, or o to other keys which are so called consonant, differed from those of inverse movements in terms of interstroke intervals.
In this research, we investigated the relation between the interstroke intervals and the finger-movements observed in typing of the visually impaired college students in detail. Concretely speaking, the interstroke intervals from vowels to others and inverse direction were measured strictly, and the differences between two movements were calculated on each visually impaired student separately.
Method
Participants
In this study, blind was defined according to the visual acuity criterion of Japan: visual acuity of 0.0 or only light perception. Participants were three blind men aged 18-23 and a man with low vision aged 68 who attended a college for the visually impaired people. The blind people had been using microcomputers for three years or more to write reports and send mails and had received some computer literacy curricula; so they operated computers relatively well for their generations. The person with low vision had had received computer training, but for less than a year.
Setting
In this experiment, participants used the Windows machines and the attached keyboards. Data were input by a given method that an experimenter indicated, though there were two major input methods to applications in Japanese language. The experiments were conducted in each participant separately in a special room for this experiment.
Tasks and Analysis
The participants were instructed to type as fast and accurately as possible the sentences that were read aloud by an experimenter. The sentences were picked out from an article on the psychology of communication. The characters corresponding to the keys pressed were displayed in a small window on the computer display and then the pressed keys and the interstroke intervals between those and the preceding keys were recorded on files. The program was described by Visual Basic. Simultaneously the experiments were recorded on videotapes that were not used in this study. The data were analyzed by t-test and were presented by using histograms.
Results
Typing errors were categorized according to the preceding study, which divided errors into three groups, that is, substitutions, omissions, and insertions. Insertion errors occurred most frequently in all the three blind participants, while substitutions occurred most frequently in the elderly participant with low vision. Accuracy of typing in each participant showed considerably high scores ranging from 97% to 99%.
Figure 1 depicts the distribution of interstroke intervals over total of 442 keypressings of a blind participant. He seemed to type relatively faster than his classmates, based on the observation by the authors in daily situations. The histogram indicates that the mode is 200ms and the longest interval is over 900ms(Mean=313, SD=362). One third of all the intervals are less than 300ms.
Fig.1 Distribution of interstroke intervals for all
keypressings
In
the Japanese language input to computer applications, elementary units are made
of one consonant and one vowel. For
example, “yama” which means mountain(s) is phonetically comprised of “ya” and “ma”,
therefore, operationally we Japanese press keys “y”, “a”, “m”, and “a” in this
order. However, in this situation, the
phonetic connection seemed to be stronger than that of simple order. Therefore, a combination of “y” and “a” may
be stronger than that of “a” and “m” which are phonetically different units,
for the former may indicate shorter interstroke intervals than the latter.
Fig2.
Distribution of interstroke intervals for movements from consonant to
vowel keys Fig.3
Distribution of interstroke intervals for movements from vowel to
consonant
Figure
2 and 3 depict the distributions of interstroke intervals of the fingers’ two
different movements. Interstroke
intervals of connections between intraphonetic consonants and vowels are
displayed in Figure 2. The histogram
indicates that the mode is 100ms and the longest interval is 900ms. Three fourth of the intervals of these
connections are less than 300ms. The
result of interphonetic connections of vowels and consonants is displayed in
Figure 3. The mode is 200ms and the
longest interval is more than 900ms.
Interstroke interval between consonants and vowels is shorter than that
of inverted connection (Mean=170 versus Mean=355,t=6.33, p<.001).
Fig.4 Relation between consonant-vowel and
vowel-consonant interval
Figure
4 is the scatter diagram that represents a relation between consonant-vowel (X-axis)
and vowel-consonant (Y-axis) interval of each participant. In three participants, marked by a square, a
circle and a triangle on the figure, the relation seems to be on some assumed
straight line. On the other hand, the
remainder locates away from the line.
As noted by the preceding study, which says that substitution errors dominated the errors of students and that they are reduced in experts, three blind participants who had used computers for more than a few years showed many insertion errors. This result seems to suggest that visually impaired people have same modifications in increasing typing experience with the sighted people.
Interstroke interval
The main aim of the study reported here is to clarify the characteristics of interstroke interval observed in different finger movements. As stated above, in the Japanese language inputs, needed are a couple of keypressings for a phonetic element with a few exceptions. Therefore it was assumed that phonetic connections that were meant to be “intraphonetic” would be stronger than interphonetic sequential one in a series of typing tasks displayed aurally in the form of continuous texts. That is, in continuous typing, it was examined whether or not the interstroke intervals between the vowel, consisting of a, i, u, e, and o, and consonant groups, consisting of k, s, t, n, h, m, y, r, and w, would be longer than those between the consonant and vowel groups.
The results of four participants showed statistically significant differences between different movements of the fingers to press appropriate keys, which indicated, as were assumed, the consonant-vowel intervals to be shorter than invert intervals. The importance of digraph, the most common two-letter sequences that cannot be pronounced separately (e.g. “th”), in the interpretation of typing mechanisms has been stressed. In the Japanese language, digraphs may be corresponded to the consonant-vowel connections. From these points of view, the instructions to teach keytypings commonly adopted in the computer literacy curriculums would be pressed to be reexamined, because it teaches the positions of keys and movements to them individually. It is important to press keys as smoothly as possible in the actual keytypings. Therefore, strong connections in intraphonetic letters would be taken into consideration at least in the early training stages.
What is the relation between the consonant-vowel connections and the vowel-consonant ones? On the limitation observed in four participants, it would be noted as only a possibility that there would be some linear relation, because three participants who indicated relatively high performance formed a line as stated in the explanation of Figure 4. But the elderly participant with low vision and with shorter training period experienced than others revealed a different relation, that the reasons will need to be examined whether it stems from the age or the training period moreover or from other reasons.
In this study, interstroke intervals were measured in the units of 100ms. Though many preceding studies have used the timer in the units of ms, this situation may be useful, at least for computer literacy training, because it doesn’t need the strictness of ms, but lenient instructions trainees can accept to set or move fingers.
Grudin, J. T. (1983) : Error Patterns in Novice and Skilled Transcription Typing. In W. E. Cooper(Ed.), Cognitive aspects of skilled typewriting. New York: Springer-Verlag.
Ishida, H.(1993) : Accuracy and Error Patterns in typing of the visually handicapped. The Japanese Journal of Ergonomics, 29(5), 321-327.
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