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Motor Skill and Dyslexia
Requests for reprints should be addressed to Dr. Angela Fawcett, Department of
Psychology, PO Box 603, University of Sheffield, Sheffield S10 2UR, UK.
Acknowledgements
The research reported here was supported by a grant from the Leverhulme Trust to the
University of Sheffield. We thank Alan Baddeley and Tim Miles for valuable suggestions for the
design of the studies. We acknowledge gratefully the dedicated support of the participants and their
parents, and the support of the teachers and pupils at Ecclesall Junior School and Silverdale
Secondary School, Sheffield.
Persistent Deficits in Motor Skill for Children with Dyslexia
Angela J. Fawcett and Roderick I Nicolson
Department of Psychology
University of Sheffield
Journal of Motor Behavior, in press
Keywords
Dyslexia, adolescents, motor skills, articulation rate.
Abstract
Three groups of children with dyslexia, mean age 8, 13 and 17 years, and three
groups of normally achieving children matched for age and IQ with the dyslexic groups
undertook three tests of motor skill. For peg placing and articulation rate, the children
with dyslexia were significantly slower than their chronological age controls, and
equivalent to their reading age controls. For bead threading, they were significantly
slower even than their reading age controls. The results suggest that children with
dyslexia have persistent, and unexpectedly severe, problems in motor skill.
Motor Skill and Dyslexia
Introduction
Children with developmental dyslexia show severe problems in learning to read and spell,
but are otherwise of average or above average intelligence. A typical estimate of the prevalence of
dyslexia in Western school populations is around 5% (Badian, 1984; Jorm, Share, McLean, &
Matthews, 1986), with roughly four times as many boys as girls being diagnosed. It has normally
been assumed that the problems of children with dyslexia derive from impairment of some skill or
cognitive component largely specific to the reading process, and one of the major achievements of
dyslexia research in the past decade was the demonstration that many of the reading-related deficits
are attributable to some disorder of phonological processing (Bradley & Bryant, 1983; Snowling,
Goulandris, Bowlby & Howell, 1986; Stanovich, 1988; Vellutino, 1979).
In addition to strong evidence of phonological deficits, in young children with dyslexia
there is also considerable evidence for a deficit in motor skills in speed of tapping, heel-toe
placement, rapid successive finger opposition, and accuracy in copying (Denckla, 1985). Children
with dyslexia, Denckla suggested, are characterised by a 'non-specific developmental
awkwardness', so that even those children with dyslexia who show reasonable athletic ability are
poorly co-ordinated. This awkwardness is typically outgrown by puberty (Rudel, 1985), leading
Denckla and Rudel to argue for a maturational lag in the 'motor analyser' which programs timed
sequential movements (Denckla, 1985). Moreover, they suggest that these deficits are primarily in
the acquisition of new tasks, which is typically awkward and effortful, but once the skill is
successfully acquired, dyslexic performance is essentially normal.
In an extensive longitudinal study, the British Births Cohort study, Haslum (1989)
examined aspects of health in a cohort of 1700 children, at birth, five and ten years. One of the
purposes of the study was to identify predictors of dyslexia in children who failed selected items of
the Bangor Dyslexia Test (Miles, 1982; 1993). Two motor skills tasks emerged amongst the 6
variables which showed significant differences between children with dyslexia and normally
achieving children at age 10, namely failure to throw a ball up, clap, and catch it again (p <.001),
together with failure to walk backwards in a straight line for six steps (p <.01).
There is also considerable evidence that children with dyslexia are impaired in articulatory
skill (Catts, 1986; 1989; Snowling, 1981; Stanovich, 1988; Wolff, Cohen, & Drake, 1984; Wolff,
Michel, & Ovrut 1990a), but it is not clear whether this is based predominantly on a phonological
or motor skill deficit in the rate or accuracy of articulation. The deficit was originally identified as
errors in the repetition of polysyllabic or nonsense words, coupled with error-free performance in
the repetition of simple high frequency words for young children with dyslexia (Snowling, 1981).
Similarly, Stanovich (1988) established that poor readers, up to age 10, showed deficits in their
speed of repetition of simple couplets, leading him to argue for a developmental lag in motor timing
control. For adolescents with dyslexia, Wolff and his colleagues identified problems in rapid paced
Motor Skill and Dyslexia
repetition of sequences (Wolff et al., 1984; 1990). The task used in the latter study was the
repetition of the sequence pa-ta-ka, entrained to the beat of a metronome. Wolff found that his
subjects had difficulty in constructing a fluent speech rhythm, particularly at the faster speeds.
Similar deficits were found for this age group in repetition of simple and complex phrases (Catts,
1986; 1989). However, though Brady and her colleagues (1989) found that 8 year old children
with dyslexia were significantly slower and less accurate in repeating polysyllables and nonsense
words, they found no impairment in accuracy or speed of a single repetition of high frequency
monosyllables. In summary, there is evidence that children with dyslexia are slower and more
error prone on complex articulation tasks, but their performance appears to be normal on simple,
familiar words.
The traditional explanation of these deficits on complex phonological tasks is in terms of a
phonological deficit (Snowling, 1981), in that children with dyslexia have problems in output
phonology, in this case in constructing a novel motor program for words they have not previously
encountered. However, an alternative viewpoint dervis from recent research into the automaticity
of motor skills in children with dyslexia. Automaticity is the final stage in learning any skill where
performance becomes expert and less demanding in terms of resources (Shiffrin & Schneider,
1977). Automatisation deficits in dyslexia were first shown by Nicolson and Fawcett (1990), who
used a dual task technique to reveal that motor skill deficits remained in balance for adolescents
with dyslexia. The study showed that children with dyslexia were able to balance normally under
'just balancing' conditions, but when they were asked to perform another task concurrently, (such
as counting, or pressing a button for a tone) their performance deteriorated significantly, unlike that
of normally achieving children. The findings have recently been extended (Fawcett & Nicolson,
1992), using a test of blindfold balance. This led to the proposal that children with dyslexia have
problems in ‘skill automatisation’ for any skill, motor or cognitive, but that for most skills children
with dyslexia learn to mask their incomplete automatisation by a process of ‘conscious
compensation’ leading to apparently near-normal performance, at the expense of greater effort.
Problems remain apparent in skills requiring rapid performance or fluent interplay of a range of
sub-skills. This is consistent with the evidence for improvement with age identified by Denckla
and her colleagues, together with deficits in complex articulation tasks, and also with deficits in
bimanual tapping identified by Wolff and his colleagues (1990b).
In principle, the area of motor skills provides the opportunity for distinguishing between the
automatisation deficit and the phonological deficit accounts of the deficits suffered by children with
dyslexia. The automatisation deficit hypothesis predicts that there will be deficits not only in
articulation skill but also in simple motor skills with no linguistic component, such as bead
threading, whereas a phonological deficit account suggests that (although there may well be an
articulatory deficit), any bead threading deficit should be relatively mild and transient. In addition
to the theoretical significance of this issue, if it were the case that motor skills were significantly
impaired in children with dyslexia, it should be possible to augment tests for dyslexia with simple
Motor Skill and Dyslexia
motor skill tests, thereby improving the diagnostic sensitivity. Indeed, this could lead to the
development of pre-reading predictive tests for dyslexia (Nicolson, Fawcett & Pickering, 1992).
The studies reported here examined these issues directly, using two tests of pure motor skill
(bead threading and peg moving) and one test of articulatory skill (speed of articulating well known
words). Furthermore, maturational changes were monitored by use of three age groups of
children. We hoped in this way not only to address specific theoretical issues but also to add to the
body of systematic knowledge about skilled performance of children with dyslexia.
Method
Participants
In order to monitor maturational change three age groups of children with dyslexia (mean
age 8, 13 and 17 years) were studied, together with three groups of normally achieving children
matched for age and IQ. This design allows not only the standard chronological age match
comparison, but also (by comparing the children with dyslexia with the younger controls) a reading
age match comparison, and even (by comparing the oldest children with dyslexia with the youngest
controls) a ‘twice chronological age’ match comparison. The reading age match comparison is
particularly important theoretically when the skill in question may be affected by reading level,
since a deficit compared with chronological age controls may indicate only a developmental delay,
whereas a deficit compared with reading age controls provides evidence of a developmental
disorder in that skill (Bryant & Goswami, 1986). Whilst the value of a reading age match is less
clear in tests of pure motor skill, use of this design allows comparison of motor skill deficit with
reading deficit, and facilitates comparison with related research on children with dyslexia.
All the children with dyslexia had been diagnosed between the ages of 7 and 10. Criterion
for inclusion was: discrepancy of at least 18 months between chronological and reading age;
together with a full scale WISC-R IQ (Wechsler, 1976) of at least 90 at diagnosis. Children whose
reading age discrepancy had reduced to less than 18 months by the time of testing were excluded.
We shall refer to the 8, 13 and 17 year old groups with dyslexia as D8, D13 and D17, with the
three corresponding normally achieving groups as C8, C13, and C17 respectively. The data were
gathered as part of a longitudinal study, with the articulation rate data gathered around two years
earlier for the older children than for the C8 and D8 groups. It may be seen (Appendix 1) that the
children were well matched on IQ and reading variables at both times of testing. The majority of
the children participated in all three tests, but there were slight differences in age and constitution of
the older groups between tests. All the children were white, drawn from social classes 1, 2, and 3
(i.e., middle class or skilled working class), and were predominantly male. Further details are
provided in Table 1.
** Table 1 about here **
Motor Skill and Dyslexia
The children with dyslexia and the normally achieving children were predominantly right
handed and matched for preferred hand. One child in each of the D17 and C17 groups preferred
his/her left hand. No independent measure was taken of the strength of hand preference.
Procedure
Two tasks were used to measure pure motor skill: a simple peg moving task and a bead
threading task. Articulation rate was measured by the repetition of simple highly familiar words.
(i) Pegboard
The pegboard used for this task was a commercially available child's pegboard consisting
of 10 rows of 10 holes. It resembled that used by Annett (1985) but was somewhat smaller (6x6
ins.). At the start of the test, the top row of the board was filled with pegs by the experimenter.
The child was instructed to move the pegs with the preferred hand as quickly as possible, jumping
over the empty row into the third row of holes, while holding the board steady with the non-
preferred hand. The children were instructed to pick up only one peg at a time, and the trial was
restarted if they picked up more. If a peg fell off the board the child was told to ignore it and carry
on. A stopwatch was used to record the time to complete each row, timed from touching the first
peg to releasing the last. At the end of the row, the children were given verbal feedback and
encouragement. They were then instructed to move the pegs a further two rows down the board,
and so on. Delay between the rows was minimal and did not vary from child to child. Testing
continued until five rows had been completed. The mean time for the five trials was the dependent
variable.
(ii) Procedure for Bead Threading
A basket containing 18 round wooden beads (4 cm in diameter with a hole of approximately
0.5 cm) was placed on the table in front of the child, and a string (85 cm long and 3 mm in
diameter) laid on the table. The children were instructed to take beads from the basket one at a
time, and thread them on the string as quickly as possible. The number threaded in one minute
(from touching the first bead) was the dependent variable.
(iii) Articulation Rate
Articulation rate was measured by asking the children to say a given word several times,
speaking as rapidly as possible. The speech was recorded onto an Apple Macintosh microcomputer
using a microphone/digitiser. The words used were bus, monkey, butterfly, with high frequency
and early age of acquisition, which were selected as representative from a larger pool of 1, 2, and 3
syllable words (Nicolson, Fawcett & Baddeley, 1992). The dependent variable was the time taken
for five repetitions, which was measured to the nearest centisecond from the digitised signal.
Motor Skill and Dyslexia
Results
Observation of performance on the three tasks suggested that on the pegboard, the D8
group showed particular difficulty, swopped between hands, and had to be reminded to move the
pegs with their writing hand. The D8 group also seemed to have greater difficulty than the controls
in threading the end of the string through the bead. In articulating the 3 syllable words, some of the
C8, the D8 and the D13 group found it difficult to generate a smooth rhythm or muddled the
syllables after several repetitions.
The mean data for all three tasks are shown in Table 2. It may be seen that the performance
of the children with dyslexia was consistently worse on all three tasks than that of the chronological
age controls. Note also the continuing improvement with age of the children with dyslexia,
whereas the controls appear to have reached ceiling by the age of 13 years.
** Table 2 about here **
Statistical Analyses
Maturational changes were assessed by using three age groups of children with dyslexia. If
a significant difference between the groups has been found in an overall analysis, two separate
issues are of interest in the statistical analyses for each experiment. First it is important to identify
whether children with dyslexia perform worse than their same-age controls. This analysis has two
factors: chronological age (8, 13 and 17 years) and dyslexia (present/absent). The second analysis
involves comparison with reading age controls (excluding the oldest controls and the youngest
children with dyslexia). It also has two factors, namely reading age (13 and 8 years), and dyslexia.
(i) Pegboard
Comparison with Chronological Age Controls. A two factor analysis of variance was
undertaken for the six groups with the factors being age (three levels) and dyslexia
(presence/absence). The main effects of both dyslexia and age were highly significant,
F(1,57)=24.4, p<.0001; F(2,57)=10.8, p<.0001 respectively. There was also a significant
interaction between age and dyslexia, F(2,57)=3.8, p<.05. .
Comparison with Reading Age Controls. A further two factor analysis of variance was
conducted, omitting the C17 and D8 group and comparing the two older dyslexic groups with their
reading age controls. The factors were therefore reading age (two levels) and dyslexia
(presence/absence). Neither the main effect of dyslexia nor the main effect of age was significant,
F(1,38)=2.5, NS; F(1,38)=3.7, NS respectively. There was no interaction between age and
dyslexia, F(1,38)=0.3, NS.
Motor Skill and Dyslexia
(ii) Beads
Comparison with Chronological Age Controls. A two factor analysis of variance was
undertaken for the six groups with the factors being age (three levels) and dyslexia
(presence/absence). The main effect of dyslexia was significant, wheareas the main effect of age
did not approach significance, F(1,56)=14.2, p<.001; F(2,56)=0.1, NS respectively. There was
no significant interaction between age and dyslexia, F(2,56)=1.4, NS.
Comparison with Reading Age Controls. A further two factor analysis of variance was
conducted, as above, with the factors being reading age (two levels) and dyslexia. The main effect
of dyslexia was significant, but the main effect of age did not approach significance, F(1,37)=10.6,
p<.01; F(1,37)=1.9, NS respectively. There was no significant interaction between age and
dyslexia, F(1,37)=0.1, NS.
iii) Articulation rate
Significant differences between the children with dyslexia and the controls were found for
each syllable length, with the pattern of results being equivalent across length.
Comparison with Chronological Age Controls. A two factor analysis of variance was
undertaken for the six groups with the factors being age (three levels) and dyslexia
(presence/absence). The main effect of age was highly significant for each stimulus type,
F(2,63)=8.9, p<.001; F(2,63)=8.5, p<.001; F(2,63)=15.8, p<.0001, for 1, 2 and 3 syllable
words respectively. The main effect of dyslexia was also highly significant for each stimulus type,
F(1,63)=15.2, p<.001; F(1,63)=11.7, p<.001; F(1,63)=15.4, p<.001 respectively. The
interactions between age and dyslexia did not approach significance.
Comparison with Reading Age Controls. A further two factor analysis of variance was
conducted, as above, with factors reading age (two levels) and dyslexia (as above). The main
effect of age was significant for each stimulus type, F(1,45)=11.3, p<.01; F(1,45)=8.2, p<.01;
F(1,45)=6.2, p<.05; for 1, 2 and 3 syllable words respectively. The main effect of dyslexia did not
approach significance, F(1,45)=1.0, NS ; F(1,45)=1.0, NS; F(1,45)=1.0, NS respectively. The
interactions between age and dyslexia did not approach significance.
Discussion
In summary, the performance of the children with dyslexia was inferior to that of their
chronological age controls on all three tests of motor skill: articulation rate, peg board, and bead
threading. Their articulation rate and speed of moving pegs were equivalent to their reading age
controls. For bead threading their performance was significantly worse than their reading age
controls. These results suggest that children with dyslexia have persistent, and unexpectedly
Motor Skill and Dyslexia
severe, problems in motor skill in even the simplest tasks. The articulation rate results extend
previous findings of a deficit in children with dyslexia, by revealing the deficit in even the simplest
one syllable words, such as bus, and that deficits at this level extended at least into late
adolescence.
In terms of the theoretical interpretation of these results, the issue under investigation was
whether motor skill deficits would persist into adolescence, and, if so, whether they would be
equivalent in severity to the articulation rate deficits (as predicted by our automatisation deficit
hypothesis) or less severe, as predicted by phonological deficit hypotheses. The results appear to
be clear-cut. There are motor skill deficits, they persist into adolescence, and they are comparable
in severity to the articulation rate deficits. These results therefore embarrass any hypothesis which
limits the deficit to purely phonological or linguistic skills. The results provide further support for
the automatisation deficit hypothesis, or, more generally, for any hypothesis which predicts
difficulties in motor skill.
It is worth exploring further the possible role of motor skill deficits as a partial explanation
of the phonological deficits known to accompany dyslexia. Consider, for instance the difficulties
with repetition of nonsense words (Snowling, 1981). Gathercole and Baddeley (1990) attribute
these difficulties to memory problems, and indeed suggest that nonword repetition may be a simple
test of memory performance. However, it is established that memory span is directly associated
with rate of articulation (Baddeley et al., 1975), and so it may be in fact that it is the difficulties in
articulation which mediate the problems in nonword repetition, rather than vice versa. Further
research is needed to assess this issue.
Regardless of the causality of the link between the motor skill deficits and phonological
deficits, it seems clear that phonological deficits alone are insufficient to explain the range of
deficits identified in this study. One recent hypothesis which provides a parsimonious account of
the range of data, including balance deficits, motor skill deficits, and timing deficits is that children
with dyslexia suffer from minor damage to the cerebellum (Fawcett & Nicolson, 1992; Nicolson,
Fawcett & Dean, 1994). Further research is needed to explore this possibility.
In conclusion, our primary motivation for this study was investigation of the issue of
whether, for children with dyslexia, pure motor skill deficits persist into adolescence. It is clear
from our results that deficits do persist in pure motor skills, in that all three groups of children with
dyslexia performed significantly worse than their chronological age controls in the three motor
skills tasks. For bead threading, their performance was significantly worse even than their reading
age controls, indicative of a developmental disorder in motor skill (Bryant & Goswami, 1986).
These findings provide strong evidence that children with dyslexia suffer from motor skill
problems which persist into late adolescence.
Motor Skill and Dyslexia
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Motor Skill and Dyslexia
Table 1. Psychometric data on the six groups of participants.
Group N IQ (WISC-R) Chronological Age Reading Age
Mean Range Mean Range Mean Range
Articulation Rate
C17 12 106.2 [92 to 130] 15.4 [15:1 to 16:0]
14.9 [14:4 to 15:0
†]
D17 16 105.0 [88 to 126] 15.5 [14:4 to 16:2] 11.8 [8:1 to 14:4]
C13 11 107.7 [94 to 126] 11.4 [9:7 to 12:9] 11.4 [9:8 to 12:7]
D13 10 111.5 [101 to 128] 11.3 [9:7 to 12:9] 8.6 [7:7 to 10:8]
C8 12 112.0 [101 to 133] 8.3 [7:9 to 8:8] 8.8 [7:7 to 10:6]
D8 8 113.8 [96 to 133] 8.6 [7:7 to 9:9 ] 6.4 [5.6 to 7.9 ]
Beads & Pegs
C17 11 107.3 [92 to 130] 17.4 [17:0 to 18:0]
15.0
†
D17 13
{11}*
105.0 [88 to 126]
{105.0 [91 to 126]}*
17.4 [16:0 to 18:2] 12.5 [8.2 to 14.6]
{13.2 [10.9 to 14.6]}*
C13 11 111.6 [96 to 129] 13.4 [13:0 to 14:4] 13.7 [12.8 to 14.6]
D13 10 111.2 [101 to 128] 13.3 [11:7 to 14:9] 9.9 [7.9 to 12.3]
C8 10 115.1 [101 to 133] 8.2 [7:0 to 8:8] 9.2 [7.7 to 11.1]
D8 8 113.8 [96 to 133] 8.6 [7:7 to 9:9 ] 6.4 [5.6 to 7.9 ]
†
15 represents ceiling on the Schonell test of reading age used. All this group were reading at this level, and the
majority had reached this level at around the age of 15.
* In order to improve the match for reading age with the 13 year old controls, two subjects were omitted from the
reading age analysis for beads and pegs. Figures in {brackets} show the psychometric data excluding these subjects.
Motor Skill and Dyslexia
Table 2. Mean Performance for the motor skills tasks
(standard deviations in parentheses).
Dyslexia Control
Group D8 D13 D17 C8 C13 C17
Beads Threaded in 60 s 9.2
(2.8)
9.3
(2.5)
10.3
(2.1)
11.9
(1.3)
12.5
(2.5)
11.3
(2.6)
Time to Move Pegs (s) 14.4
(2.3)
11.7
(1.5)|
10.3
(0.9)
10.4
(1.3)
9.7
(1.1)
9.4
(1.1)
Articulation time for 1
syllable words (s)
0.46
(0.18)
0.39
(0.22)
0.28
(0.07)
0.34
(0.06)
0.24
(0.03)
0.24
(0.05)
Articulation time for 2
syllable words (s)
0.56
(0.21)
0.45
(0.20)
0.38
(0.11)
0.44
(0.05)
0.32
(0.07)
0.33
(0.08)
Articulation time for 3
syllable words (s)
0.78
(0.11)
0.61
(0.20)
0.55
(0.14)
0.62
(0.07)
0.50
(0.06)
0.47
(0.08)