The Differences in Coordination between Children
with ADHD and Healthy Children Based on Two-

way ANOVA Analysis
jiahai Liu1 gao Yang1 fangzhong Xu minyan Zhou

1:Zhejiang University City College, Hangzhou, China

1

2:Zhejiang Palit Hospital, Hangzhou,China

Abstract—This study attempts to invest the differences in
movement coordination between children with ADHD and
healthy children using two-way ANOVA. The experimental tasks
are divided into simple task and complex task. The goal of the
experiments is to study the interaction in hand movements’
rhythm, accuracy and error key response between task difficulty
and subjects grouping while doing visual-motor integration tasks.
The results show that: (1) There are no significant differences in
all parameters except error number within group differences. (2)
There are significant differences in all parameters except correct
response time between group differences.

Keywords-task difficulty; ADHD; grouping; movement
coordination

I. INTRODUCTION
Attention deficit hyperactivity disorder (ADHD) is very

common in clinical, it is one of the most widely studied
diseases in child psychiatry[1-5]. In recent years, it ranks in the
first or second place in the child-patient cases, causing the
whole society’s attention on children with ADHD.

Children with ADHD often accompany with developmental
disabilities, the most common is developmental coordination
disorder (DCD). This is a special developmental disorder, is
characterized by obvious damage in the motion coordination[4-
5]. Although motor coordination disorder and ADHD are two
different developmental disorders, but the studies find that
ADHD often accompanies with motor coordination
disorders[6,7]. Although many of the motor need the
participation of many senses, but visual sense is the most
important. Visual – motor integration is developed firstly in
sensorimotor integration, coordination between visual
perception and hand movements reflects the coordination and
unification between visual perception and activities[8].

At present, continuous performance tests (CPT) are used to
evaluate attention disorder among children. A series of
numbers or characters are showed on a computer monitor as
stimulants in a CPT, subjects are required to make response to
certain target, the reaction results are used to evaluate attention
deficit. Error number in the tests is used to reflect the subjects’
attention deficit, false number reflects the impulse of subjects.
As that, the objectivity of evaluation has been improved greatly
and the accuracy of clinical diagnostic is higher. Andrew L.
Cohen [4] considers that CPT has moderate reliability and
validity in the diagnosis of ADHD. Wang shu-yu[5], finds that
in auditory continuity tests and audio-visual continuity test, the
reaction time of children with all ADHD subtypes are longer

than those of control group, and the number of misstatements
and omissions are significantly higher than those of control
group. However, And Gayle finds that hit rate of ADHD
children is lower than that of normal control group in the
single-target CPT, but in the sustained attention task there is no
significant difference between them. The reason may be the
study ignores the temporal characteristics attention, we should
notice that attention changes over time, itself will produce the
ups and downs over time, the performance of subjects is good
at the beginning of the test, and then declines. The researches
on ADHD children’s cognitive mechanisms have unanimously
recognized that children with ADHD lose more short-term
attention that normal children, and the short-time attention of
them have great fluctuations than that of normal children.
Besides that, children appear to lose attention to the test if the
test is distracting, this also needs to be examined depending on
the time.

Raising the level of any researches are inseparable from the
improvement of methods. Traditional ADHD researches are
usually horizontal studies, often using large samples, real-time
facilities to measure and compare the mean, variance analysis,
differences in test, and finally get the conclusions. Longitudinal
study is an extension in the psychology research methods, it is
closer to the true law of development of the psychological
phenomenon. Time series test is a longitudinal study, it refers
to the values of certain indicators at different times,
chronologically arranged in the series; also refers to a system in
response to the different “time” which is its own historical
behavior objective record. Time series tests can observe long-
term trend of variables and the trend of the psychological
development of individuals. They can also determine the causal
relationship between the variables on the dynamic changes, as
well as long-term prediction and control of human psychology
and behavior.

Previous studies of motor coordination in children with
ADHD use several common sensory integration scales, the
results depend on the observation, are not subjective. And the
studies only examine motor coordination in children with
ADHD, haven’t studied the factors affect coordination.
Therefore, this article studies the difference of coordination
between children with ADHD and normal children, and tries to
explore the influence of difficulty levels of tasks on motor
coordination, with a goal to provide new experimental
evidence to coordination study of ADHD.

Zhejiang Provincial Natural Science Foundation (Y2080622)

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II. METHODS

A. Subjects
Experimental group: Randomly select 20 children with

ADHD from Tongde Provincial Hospital, Hangzhou, aged 7-14
years old. Inclusion criteria: (1) Comply with the American
Psychiatric Association “Diagnostic and Statistical Manual of
Mental Disorders,” Fourth Edition (DSM-IV) ADHD
diagnostic criteria. (2) Exclude people with physical disease
and extensive mental disorders, mental retardation, emotional
disorders and other diseases. (3) All cases are not under
spiritual drug treatment. (4) All cases are right-handed.

Control group: Randomly select 20 normal children from
primary school grades 1-6, Hangzhou, aged 7-14 years old.
Exclude people with physical disease and mental illness.
Children are right-handed.

B. Laboratory instruments and materials
The experiment is controlled by a personal computer, the

screen resolution was 1024 × 768. Stimulus materials are the
Arabic numerals 1-3, the size is 3cm × 3cm, the color is red.
Stimuli are presented in the center of 14-inch color display,
response keys were “1”, “2”, “3”.

C. Experiment design
The experiment takes a two-factor variable(subjects:

children with ADHD and normal children ×difficulty levels of
tasks: simple and complex ) in experiment design. Dependent
variables are reaction time (RT), reaction time fluctuations,
the correct key number, missing number, wrong number and
extra number. Among them, reaction time fluctuations( RT)
means the absolute value of the difference between adjacent
two reaction time.

D. Experiment process
This study takes place in the psychological tests room, it’s a

quiet test environment without any interference. First
experimental objects are informed to the subjects. Before the
experiment, participants take enough practices. During the test,
random number from 0 to 9 are displayed in the middle of the
screen, each number lasts for 100ms and the duration of two
numbers is 1900ms. After subjects see the number, they are
asked to press the same number on the keyboard. The whole
test lasts for 40 minutes, and every minute is a sequence, every
number will be displayed once in a sequence. The computer
automatically records correct number, miss number, error
number and average reaction time. The correct number is used
to mainly reflect the sustained attention in the study.

Simple experiment: During the experiment, Arabic
numerals 1-3 will randomly appear in the middle of the
computer screen, each number will continue to appear 3 times.
Stimulus duration is 100ms, the time between two appearances
is 900ms, when the subjects see the number appears, they are
asked to press the corresponding number key.

Complex experiment: Based on the sub-experiment 1,
computer randomly set the occurrences of number, it’s
unpredictable, increasing task difficulty, and subjects are asked

to remain vigilant. During the experiment, Arabic numerals 1-3
will randomly appear in the middle of the computer screen.
Stimulus duration is 100ms, the time between two appearances
is 900ms, when the subjects see the number appears, they are
asked to press the corresponding number key.

III. RESULTS
Table 1&2 show the reaction time (RT), reaction time

fluctuations, the correct key number, missing number, wrong
number and extra number while two groups doing simple
experiment and complex experiment. Independent samples T-
test in table 1 show that there are significant differences in
reaction time fluctuations, correct number, wrong number and
extra number between two groups. Compared with normal
children, children with ADHD have large reaction time
fluctuations which means children with ADHD have larger
change in rhythm and their movement is more instable.
Children with ADHD have less correct number and more
wrong number than normal children, which means the visual-
motor integration accuracy and hand motor coordination of
Children with ADHD are worse than those of normal children.
Children with ADHD also have more extra number than
normal children, it reflects that hand movements of ADHD
children are more confused and have less coordination. There
is no significant difference in reaction time between two groups,
indicating that there are no difference in speed of visual-motor
integration and speed of hands movement between two groups.

TABLE I. THE DIFFERENCE IN PARAMETERS BETWEEN TWO
EXPERIMENTS AMONG CHILDREN WITH ADHD

Simple task Complex task
Mean Std.

Deviation
Mean Std.

Deviation
Reaction time 343.2000 51.5855 366.1000 58.7829
Reaction time
fluctuations

202.9000 40.8260 213.1000 36.7709

Correct number 595.6000 202.4034 527.8000 114.2509
Wrong number 157.6000 94.1348 296.6000 103.8890
Miss number 163.7000 229.8478 103.6000 55.2272
Extra number 566.8000 763.2151 426.300 274.0170

TABLE II. THE DIFFERENCE IN PARAMETERS BETWEEN TWO
EXPERIMENTS AMONG HEALTHY CHILDREN

Simple task Complex task
Mean Std.

Deviation
Mean Std.

Deviation
Reaction time 371.5000 64.8249 385.5000 48.4865
Reaction time
fluctuations

128.7000 30.2142 102.9000 21.5481

Correct number 797.1000 69.7176 771.1000 56.0306
Wrong number 47.5000 36.2713 78.4000 32.1565
Miss number 51.6000 51.0385 53.5000 44.6672
Extra number 54.3000 47.5863 71.6000 51.2622

Independent samples T-test in table 2 shows: (1) There are
differences in reaction time fluctuations, correct key number,
wrong number of keys and extra number keys between children
with ADHD and healthy children both in simple task and
complex task; (2) There is no difference in reaction time
between children with ADHD and normal children, we indicate
that there is no significant difference in the speed of visual –
motor integration between two groups, maybe there is no

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difference in some terms of cognitive processing between them,
but it needs further experimental verification.

Table 3 shows the influence of subjects grouping and task
difficulty on parameters based on two-way ANOVA. The
results show that there is difference in error number between
two groups and the interaction is shown in figure 1. The results
of simple main effects test are shown in table 4.

TABLE III. THE INFLUENCE OF SUBJECTS GROUPING AND TASK
DIFFICULTY ON PARAMETERS

Reactio
n time

Reactio
n time

fluctuati
ons

Correct
number

Wrong
number

Miss
number

Extra
number

Sub
ject

s
gro
upi
ng

F=1.796 F=77.34
9

F=31.90
0

F=48.98
2

F=4.350 F=11.35
2

P=.189 P=.000*
**

P=.000*
**

P=.000*
**

P=.044* P=.002*

Tas
k

diff
icul
ty

F=1.075 F=.554 F=1.149 F=13.11
9

F=.560 F=.229

P=.307 P=.462 P=.241 P=.001* P=.459 P=.635

Inte
ract
ion

F=.063 F=2.938 F=.282 F=5.311 F=.636 F=.376
P=.804 P=.095 P=.599 P=.027* P=.431 P=.544

TABLE IV. SIMPLE MAIN EFFECTS OF SUBJECTS GROUPING AND TASK
DIFFICULTY

Mean Std.
Deviation

F P

Simple task Healthy
children

47.5000 36.2713 11.911 .003**

Children
with ADHD

157.6000 94.1348

Complex
task

Healthy
children

78.4000 32.1565 40.256 .000***

Children
with ADHD

296.6000 103.8890

Healthy
children

Simple task 47.5000 36.2713 4.064 .059

Complex
task

78.4000 32.1565

Children
with ADHD

Simple task 157.6000 94.1348 9.830 .006**

Complex
task

296.6000 103.8890

Figure 1. Interaction between subjects grouping and task difficulty on error
number

Simple main effects analysis shows that there are
significant differences both within groups and between groups.
The difference is even more significant while doing complex
task, which means that task difficulty has influence on the
accuracy of visual-motor integration, the more complex the
task is, the greater the impact is. There is significant difference
between two levels of task difficulty only in children with
ADHD, however there is no significant differences in healthy
children. The results show that task difficulty does not affect
the error number of healthy children, but has a certain effect on
that of children with ADHD, the error number significantly
increased while children with ADHD are doing complex task.
It shows that among children with ADHD, the more complex
the task is, the worse accuracy of visual – motor integration is,
and the worse movement coordination is.

IV. DISCUSSION
This study invests the differences in movement

coordination between children with ADHD and healthy
children while doing simple task and complex task based on
two-way ANOVA analysis. The study finds that: (1) There are
differences in reaction time fluctuations, correct key number,
error number of keys and extra number keys between children
with ADHD and healthy children regardless of task difficulty;
(2) Task difficulty has no influence on reaction time, reaction
time fluctuations, correct key number and extra number keys.
The reason is that the coordination of children with ADHD is
poor and their performance is bad both in simple task and
complex task. But within the healthy children the task is not
hard enough to make difference performance; (3) Compared
with simple task, the error number of children with ADHD
increases while doing complex task. It shows that children with
ADHD are easier to make mistakes while doing complex tasks;
(4) There is no difference in reaction time between children

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with ADHD and normal children, we indicate that there is no
significant difference in the speed of visual – motor integration
between two groups, maybe there is no difference in some
terms of cognitive processing between them, but it needs
further experimental verification.

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