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According to an investigation
of braille reading rates in congenitally blind youths (Kurokawa, 1987),
thirty eight percent of the subjects could read aloud Japanese reading
materials above 110 wpm. Of those subjects who were evaluated as excellent
braille readers, only one person used her left hand exclusively, but the
remainder were both hand users with a right hand superiority in reading.
When observing excellent
readers' behavior, we find that the index fingers of both hands begin to
scan together at the first of a line, the left index finger leaves at the
middle of the line to detect the top of the next line, and the right hand
alone goes over the remaining part of the line. From the viewpoint of tactual
behavior, most of the region of braille text is felt by the right hand
not by the left.
We know that the right hemisphere
of the brain is responsible for pattern recognition and the left brain
mainly acts as language center on the basis of the asymmetry of brain function.
As the motor control and sensory pathways between the hand and the hemisphere
are crossed, the information from the left hand is projected on the right
brain and the left brain gets the information by the right hand. And we
know that words are processed more efficiently when presented in the left
brain, whereas for pictures, more efficiently in the right. It is also
argued that the left hemisphere operates in a serial and analytic fashion,
and the right hemisphere operates in a parallel and holistic fashion. Now,
if braille reading is intimately related with language processing, it would
be suggested that the braille information gotten by the right hand is efficiently
processed in the left brain. In the investigation mentioned above, all
of the subjects who read with both hands and showed left hand dominance
could not gain above 110 wpm. But, only one subject who was a left hand
reader could read the materials at 142 wpm. It would be suspected that
the use of the right hand is crucial for reading braille, or the left hander
who was excellent in the investigation above processed braille information
in her right brain. However, we have not been able to obtain any evidence
of the relationship between hemispheric function and braille reading.
As medical science advances,
such severe disorders which caused total blindness before have been able
to be maintained at a level of low vision. For those people, continuous
medical examination has to be indispensable and there may be a serious
threat of becoming blind near future. Although we prepare resources with
large type for them to promote efficient learning, some students may have
need of reading braille in their learning situation.
Now, do the readers with
low vision show a similar trend as the congenitally blind in braille reading?
That is, with which hand they use mainly in reading braille? If it would
be suggested that they read braille by means of converting tactual information
into visual images, the braille reading with the left hand might be promoted.
A tentative experiment was conducted to examine whether low vision people
showed hand dominance in the reading and discrimination of braille.
Experiment I Braille reading rates in low vision subjects
Purpose
To examine whether there
was a trend of hand dominance in braille reading of the subjects who had
visual imagery.
Method
Subjects: Three students
(1 male and 2 females) with low vision in Tsukuba College of Technology
who could read braille to some extent served as subjects in this experiment.
The mean age was 21.3 years and the range was from 19 to 25 years. All
were right handed by Bradshaw's nine items (1982).
Materials: A text of natural
science description was selected for the reading material and divided into
fifteen sections for the experiment. The mean words of fifteen reading
materials was 112.3 in the meaning unit of Japanese, called Bunsetsu. The
range of words (Bunsetsu) was from 83 to 179.
Procedure: Individual subjects
read braille materials in three ways; with the left hand, the right hand
or both hands. Each subject read five materials in one hand condition,
and the total number of the trials was fifteen. The order of which hand
condition was adopted at a certain trial was randomized.
Results
Figure 1 shows the braille
reading rate of each subject. The grand mean of reading rates in three
subjects was 20.57 wpm and ranged between 7.5 wpm and 31.9 wpm. It was
clear that those subjects were categorized as poor readers of braille.
Though two subjects had a tendency to read faster with both hands than
with one hand, all of the subjects obviously showed left hand superiority
of braille reading. This trend was statistically significant of every subject.
An analysis of variance (ANOVA) was performed in each subject on the reading
data when the braille reading rate (wpm) was designated as dependent variables
and the hand condition (both, left or right) was as independent variable,
and it showed that the main effects of all subjects were highly significant
(AN: F(2, 12)=32.475, p<0.01; HW: F(2, 12)=98.247, p<0.01; IT: F(2,
12)=9.926, p<0.01) and the reading speeds with the left hand were significantly
faster beyond the 0.01 level than with the right hand by the Tukey multiple
comparison test.
Experiment II Discrimination of braille patterns
Purpose
To examine the relationship
between the braille reading rate and the response time for making the discrimination
of braille patterns. That is, it was intended to examine whether the left
hand superiority in the braille reading task would be also shown in the
discrimination task of braille patterns.
Method
Subjects: The participants
of this experiment were three, who were the same as in Experiment I.
Materials: The stimuli for
discrimination were selected braille cells constituted from two to five
dots, and arranged half as same pairs and the other half as different pairs.
In the pairs of which two stimuli were the same, the stimuli were selected
out of braille cells constructed from two, three, four and five number
of dots. As the pairs with the same number of dots were prepared five sets
respectively, the total number of same pairs turned out to be twenty. On
the other hand, the braille pairs which were different from each other
were divided into four categories. The first category was the pairs which
were different from the shape and the number of dots (dif), the second
was the pairs of the different shape but same number of dots (dform), the
third was the different number of dots but similar in shape (mid), and
the last category was the pairs of symmetrical shape (sym). As the pairs
of each category were five, the total number of different pairs were twenty.
Therefore, forty pairs were prepared for one session of the experiment.
Procedure: The experimenter
presented one stimulus pair at a time to each subject, and asked him/her
to judge whether two patterns were the same or different. The response
times were recorded with a stop watch. Individual subjects made judgments
in two sessions with the right hand and in other two sessions with the
left hand. The order of which hand was adopted in a session was randomized.
Results
Figure 2 shows the result
of the discrimination tasks. An ANOVA was performed in the way that the
response time was a dependent variable, and the pairs (same or different)
and the hand condition (right or left) were as independent variables. As
a result, one subject (IT) made faster judgement with left hand than with
the right (F(1, 156)=29.381, p<0.01), but the other two subjects did
not show such a hand dominance in over all discrimination performances.
IT was the poorest reader in this experiment, and she showed left hand
superiority in both tasks of the reading and discrimination of braille.
The other subjects, who read braille faster that IT, did not show the significant
hand dominance in the discrimination tasks unlike in the task of braille
reading.
Figure 3 shows the response
times in the subjects when two stimuli were the same braille cells. The
ANOVA was performed when response time was a dependent variable and as
independent variables were designated as the number of dots (4 levels)
and the hand condition (the right or the left). There was a tendency of
increased response times with increasing the number of dots in two subjects
( IT: F(3, 72)=3.893, p<0.05; HK: F(3, 72)=7.936, p<0.01). In IT,
it is shown that the response times almost linearly increased with the
number of dots, and the response time with the left hand was significantly
faster than with the right (F(1, 72)=14.283, p<0.01). As the interaction
between the number of dots and the hand condition was not significant,
the relationship between the number of dots and hand condition was similar
in the situation with both hands in this subject.
Figure 4 shows the result
of the response times when the two stimuli were different from each other.
As the figure shows, subject IT was much slower than the other two subjects,
but there was no tendency between response times and the categories of
stimulus for three subjects. The ANOVA did not show significant main effects
for the category (4 levels) and the hand condition (the right or the left).
However, in subject AN, his left hand seems to be sensitive to the braille
patterns because the left hand responded faster than the right (F(1, 72)=6.357,
p<0.05).
Discussion
First issue of the results
in this experiment is the left hand superiority in braille reading for
the three subjects with low vision. Each subject answered introspectively
that he/she had mental pictures of braille cells or Kana letters during
braille reading tasks. One possibility is that braille information gotten
by the hand is transferred into visual images, and recognized as letters
for language processing.
The second is the issue
of the relationship between braille reading and the discrimination of braille
cells. The left hand dominance for braille discrimination tasks showed
in a poor reader. However, in the subjects who could read braille to some
extent, there was no hand superiority for response times in discrimination
tasks. It may be suggested that a factor which influences on the left dominance
in their reading braille is not on a perceptual level to distinguish individual
braille cell each other, but on a linguistic level to comprehend language.
The third is that in two
subjects, the response times in discrimination tasks increased with the
number of dots, but did not show the difference among the categories designated
in the term of shape. For these subjects, the difference of the number
of dots was crucial for braille discrimination, not for the characteristic
of braille shapes. Although it was not statistically significant, an interesting
result was that stimulus pairs with two dimensions, such as shape and the
number of dots, had the fastest response time in two subjects.
References
Bradshaw, J.L., Nettleton, N.C., and Spehr, K. (1982) Braille reading and left and right hemispace. Neuropsychologia, 20, 4, 493-500.
Kurokawa, T. (1987) Four strategies in reading braille. Japanese Journal of Psychology and Education of the Blind, 5, 1, 1-6. (in Japanese)