Infant Behavior Simulation
Based on an Environmental Model anda Developmental Behavior Model∗
Yoshifumi Nishida
Digital Human Research Center
AIST & CREST, JST
2-41-6, Aomi, Koto-ku, Tokyo
135-0064, Japany.nishida@aist.go.jp

Koji Kitamura
Mechanical Engineering Department
Tokyo University of Science
2641,Yamazaki, Noda-shi, Chiba
278-8510, Japank.kitamura@aist.go.jp

Yoichi Motomura
Digital Human Research Center,
AIST & CREST, JST
2-41-6, Aomi, Koto-ku, Tokyo,
135-0064, Japany.motomura@aist.go.jp

Hiroshi Mizoguchi
Mechanical Engineering Department
Tokyo University of Science
2641, Yamazaki, Noda-shi, Chiba,278-8510, Japanhm@rs.noda.tus.ac.jp

Abstract – A computational approach to understanding
comprehensively the behavior of infants and children, whichis required in clarification of the dynamics of a system that
includes behavior-related accidents, is needed. The present
paper describes a method for simulating infant behavior ina virtual environment. The determinant factors of infant behavior are classified into internal factors, such as the physical and cognitive capabilities estimated from the age of theinfant, and external factors, such as visual stimuli from surrounding objects. An infant behavior simulator is developed
herein by modeling these internal and external factors. The
present paper reports the effectiveness of the newly developed simulator. This simulator enables analysis of infant accidents at home from an engineering point of view and will
support the design of rooms and houses that are safer for
infants.
Keywords: Behavior simulation, Behavior model, Accidents involving children

1 Introduction
A recent report[1] states that unintentional injury is theleading cause of death among children below 14 years of age,even though the rate of injury has declined approximately
40% over the last ten years. In the United States, unintentional injury claims more than 5,600 lives a year, or an average of 15 children each day. In Japan, unintentional injury∗ 0-7803-8566-7/04/$20.00 
c 2004 IEEE.

is also the leading cause of death among children and accounts for 21.7% of child fatalities. This report clarifies thenecessity to recognize child injury as a public health issue,
amenable to prevention, rather than as the result of uncontrollable ”accidents”. Techniques for analyzing child behavior are required for the prevention of unintentional injury ofchildren at home and for the design of safer environments forchildren.
A computational approach makes it possible to integrate
existing knowledge on infant behavior in various research
fields and to analyze infant behavior more comprehensively
than is currently possible in research fields such as cognitive
science or developmental behavior of children.
The present study attempts to establish both a computational approach to understanding child behavior and the dynamics of a system that takes child behavior into account.
In addition, a comprehensive and concrete demonstration of
the effectiveness of the proposed approach is given by applying the approach to technologies used in preventing childinjury and to the construction of an environment that is safe
for children.
As a first step, this paper focuses on the behavior of young
children1, including infants and toddlers, for the following
reasons:• Infants have the highest rate of unintentional-injuryrelated death.
1 In this paper, the term ”infant” refers to children under three years of

age

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• The developmental behavior of infants has beenclarified[2, 3].

• Rapid development of infant abilities and bodyshape
The cognitive and behavioral ability of infants develops more rapidly than those of both older children andadults. The physical shape of infants also changes
rapidly. Therefore, it is difficult for parents to predict
their behavior, even though it is simpler than that of
adults.

• In the earliest stage of the science of child-related accidents, overly complex factors, such as a high level ofcognitive abilities, are avoidable, and these can be integrated into the approach incrementally after developing
the basic approach.
This paper presents an infant behavior simulator that simulates infant behavior in a virtual environment. In the next
section, we analyze the factors related to infant injury accidents at home and clarify the necessary functions of infant
behavior simulation. Section 3 presents the newly developed
prototype system for infant behavior simulation. In Section
4, we describe the significance of the simulation and infant
informatics based on the simulation techniques.

• Environmental disparity among individuals
The arrangement and type of furniture differs among individual homes and can change dynamically. Currently,
there are no methods for preventing accidents that canbe applied universally.
• Difficulty in watching infants 24 hours a day
It is impossible for parents to monitor their infants 24hours a day, and many accidents occur when a parent isnearby.

2 Infant Behavior Simulation
2.1 Analysis of factors in accidents involving
infants at home
Key factors in accidents involving infants have been reported to include environmental factors (e.g. neighborhood
cohesion), parent-related factors (e.g. functionality of family, income, gender of the head of the household, and parenting), and infant-related factors (e.g. age, temper, and history
of injuries), as shown in Fig. 1 [4]. In this way, the system offactors affecting accidents involving infants is complex. The
dynamics of the system should be clarified in order to help
prevent such accidents.

2.2 Necessity of infant behavior simulation
The necessity of infant behavior simulation, i.e. a computational approach, is shown by the following:• Necessity for dealing with a complex system of accidents
A number of accidents occur due to a combination ofmultiple factors, such as infant abilities, environmental
factors, and parent behavior. A computational approachenables us to integrate these factors using a computer
and to conduct an analysis-by-synthesis, so that we cananalyze and clarify the dynamics of a system of accidents.

Mutual int
era
cti
o

Environment
furnitureother objects
their arrangement
temperatureneighborhood
...
...

n

• Necessity for describing knowledge on a computer
Once the factors behind accidents and scientific knowledge of infant behavior are described on a computer, we
can evaluate and utilize the computerized knowledge invarious applications.
• Necessity for real-time and one-step-ahead monitoring
Ubiquitous sensors[5, 6] for monitoring infant behavior
may be available for home use in the near future. Basedon simulations, in addition to real-time monitoring of
infant behavior, one-step-ahead monitoring is needed inorder to prevent injury accidents.

Infant accidents

Infantage
behavior
development of behavior
tempergenderexperience of injury
healthphysiological status...
...

Parent &Persons in the household
gender of household's head
incomeexperience of parenting
family functioning
number of persons in the household...
...

• Dealing with the ”human element”
It is impossible to analyze accidents by setting up ”artificial accidents”. This presents a difficult problem for
dealing with accidents scientifically. One solution tothis problem is to utilize a database of past accidents.

Figure 1: System of factors affecting accidents involving infants

2.3 Fundamental functions of the infant behavior simulator

The key causes of accidents involving infants at home areas follows:This section describes the fundamental functions of theinfant behavior simulation.

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• Function for integrating key components affecting
infant behavior
In this paper, we classify the determinant factors of infant behavior into internal factors, i.e., the physical andcognitive capabilities estimated from the infant’s age,and external factors, i.e., visual stimulus from the environment surrounding the infant. A developmental behavior model for describing the internal factors and an
environmental model for describing the external factors
are presented in detail in the next section. Integrationof these two models makes it possible to analyze thedynamics of infant-behavior-related injury accidents bychanging key parameters (e.g., infant’s age and arrangement of furniture) that affect infant behavior.
• Function for utilizing simulation results in practicalapplication
Infant behavior simulation will have various applications, such as the computer-aided design of a safe environment or the development of a real-time monitoring
system for accident prevention. This paper presents thecreation of a hazard map as one of fundamental functions in designing a safe environment.

3.2 System components
3.2.1 Accident database
An accident database was created using data from over
200 injury accident incidents collected with the cooperationof a doctor at a children’s hospital. The database includes
information that includes date, name, age, accident location,
type of injury, causative behavior, and causative object.

3.2.2

Environmental model (environmental
database)

The environmental model describes the object characteristics. In this research, an object is considered to be anythingthat can induce infant behavior. The environmental model
includes information on the infant behavior that is inducedby the object. The induced behavior is determined using past
accident data and data collected in a behavior observation
room developed by the authors. The details of the behavior observation room are presented in Section 3.4. The label
expressing the induced behavior is selected from the list of
behaviors of the developmental behavior model presented in
Section 3.2.3.

1. Name(e.g., house plant)
2. Position(e.g., (1500,200,0))
3. 3D CAD/graphic data
(e.g., house_plant.3ds)
4. Position of accident-related part(e.g., leaf,soil,pot)
5. Induced behavior(e.g., pull_oneself_up, falling, pick_up.
The behavior is selected from thebehavior defined based on DENVERII)
6. Induced physiological phenomena(e.g., airway obstruction, bruise.
The phnomena is described in relation
to the induced behaivor.)

3 Development of an Infant Behavior
Simulator
3.1 System configuration
We created a prototype infant behavior simulation system.
The simulator consists of an infant accident database, an infant developmental behavior database, an object database, asimulation engine and a visualization engine.

Environment/Object DB
Developmental behavior DB

Figure 3: Data structure of an object

Infant accident DB
SQL Server
LAN

Operation GUI(Set parameters, registration)

Visualization engine(Unreal CG engine)

Infant behaivor simulationengineFigure 2: System configuration

3.2.3

Developmental behavior model (Developmental behavior database)

We based the developmental behavior model on DENVER II[2, 3], which was originally used for evaluating thedevelopmental level of infant behavior. Some examples ofrough-and-large behavior of the entire body used in DENVER II are ”lie on infant front”, ”roll over”, ”lie face up”,
”crawl”, ”sit”, ”stand”, ”fall”, ”walk”, ”run”, ”jump”, ”pulloneself up”, ”walk backward”, ”climb up”, ”kick”, ”throw”,”stand on one foot”, and ”pick up”. Some examples ofrough-and-large behavior of the hands are ”place hands together”, ”reach hand for object”, ”rake with hand”, ”holdobject in both hands”, ”change hands”, ”pinch with thumb”,
and ”move only thumb”. The developmental behavior model
includes a list of the above behaviors in relation to infant age

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and state transition of behavior. An example of the state transition used in the model is shown in Fig. 4. The state transition changes largely depending on age, as shown in Fig. 5.
In Fig. 5, the left-hand side of each of the six figures indicates the state transition related to rough-and-large behaviorof the hands, and the right-hand side of these figures shows
the state transition related to rough-and-large behavior of theentire body. The figure indicates that the transition becomescomplex as the infant becomes older.

3.2.4

Visualization

Visualization is realized using UnrealEngine2[7], which isoriginally a graphic engine for creating video games. The
simulation engine generates the behavior that can be performed by the infant at a given moment and sends the behavior data to the visualization engine via TCP/IP. The visualization engine then displays the infant’s behavior in thevirtual room, as shown in Fig. 6.

Figure 4: State transition for the case of a 1.5-year-old child0 month

3 months

Figure 6: Example of visualization of behavior simulation

3.3 Simulation flow
6 months

The steps for generating infant behavior are as follows:

9 months

1. Get list of possible behaviors (Behavior set Bd ) fromthe developmental behavior model by inputting the infant’s age.

12 months

2. Calculate distances from the infant to objects and findthe nearest objects.

15 months

3. Get list of induced behaviors (Behavior set Bi ) from theenvironmental model of the nearest objects.

Figure 5: Change in the state transition of behavior with respect to infant age

4. Get the product set Bd ∩ Bi of Bd and Bi .
5. Generate the next infant behavior by selecting an element from Bd ∩ Bi .

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6. If necessary, search potential injury accidents using theselected behavior.

Small type(28x20x17mm)

Tiny type(12x12x20mm)

Long life
battery type(65x44x20mm)

7. Repeat 2 to 6.
The infant simulator can be used for hazard analysis. If
we can define hazard levels of accidents, the simulator cancalculate a hazard map of the room, as shown in Fig. 7. In
this figure, the red areas indicate high hazard levels.

Tag

Figure 8: Behavior observation room equipped with ultrasonic location sensors and a camera

3500
3000

Chair

2500
2000
Table

mm

1500

Figure 7: Example of a hazard map created based on theinfant behavior simulation

Chair

1000
Chair

500
0
-500
-1000

3.4 Behavior observation room
Observing infant-object interaction is important in orderto create a model of how objects affect infant behavior. As
such, we constructed a behavior observation room in orderto study how infants interact with objects and furniture.
Figure 8 shows the behavior observation room, in which
ultrasonic location sensors[8] and a camera are installed. The
ultrasonic location system consists of an ultrasonic receiving system, an ultrasonic transmission system, a time-offlight measurement system, a network, and a personal computer. The ultrasonic receiving system receives ultrasonicpulses emitted from the ultrasonic transmitters and amplifies
the received signal. The time-of-flight measurement system
records the travel time of the signal from transmission to reception. The network synchronizes the ultrasonic location
system and collects time-of-flight data from the ultrasonic receiving system. The positions of objects are calculated basedon more than three time-of-flight results. The sampling frequency of the proposed ultrasonic location system is 50 Hz.
The proposed system can detect the positions of objects andinfants within 30 mm for all objects/infants to which ultrasonic transmitters are attached (ultrasonic 3D Tag in Fig. 8).
Figure 9 shows the measured trajectories of an infant when
the infant moves as shown in Fig. 10.

-1500
-2000

-1000

0

1000

2000

mm

3000

4000

5000

Figure 9: Example of measured trajectory for a 1.5-year-old
child

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Figure 10: Example of infant activities4 Significance of the infant behavior
simulation
This section describes the significance of the proposed infant behavior simulation.
• Helpful in designing an environment that is safe for
infants
In designing ordinary homes, nursing homes, daycare
centers for children, and kindergartens, for example,
the safety of such environments can be evaluated in advance. The proposed simulator will also make it possible to improve existing homes in order to reduce therisk of injury accidents involving infants.
• Helpful in educating parents for the purpose of preventing accidents
Knowledge applicable to individual homes can be obtained in order to help prevent injury accidents. Effective education will be possible by combining the simulation with realistic graphics.
• Real-time monitoring of infants for the purpose of
preventing accidents
Real-time monitoring of infants in order to prevent accidents will be possible by integrating the proposed simulation and a sensing system. Inexpensive sensors, sensor networking technology, and ubiquitous computing
technology have already been developed.
• Development of infant informatics
The proposed simulation contributes to the development of a new research area, which can be referred toas infant informatics or child informatics. Infant informatics attempts to comprehensively understand infant
behavior by considering infant behavior from an informatics perspective.

5 Conclusions
This paper described the necessity for scientific studyof infant-related injury accidents, the associated difficulties,
and the significance of a computational approach as a method
to address the problem of child safety in the home. As one
computational approach, the authors proposed an infant behavior simulation system that enables the simulation of infant behavior in a virtual environment based on past accident
data. To create the simulator, the authors classified the determinant factors of infant behaviors as either internal factors or
external factors. The internal factors were modeled as a developmental behavior model. The model describes behaviors
displayed by an infant in relation to the infant’s age. The capabilities are modeled using knowledge of the developmental
behavior of infants. The external factors were modeled as anenvironmental model that includes objects around the infant,as well as their positions. The environmental model contains
information on the behavior induced by the objects surrounding the infant. The infant behavior induced by the object
was selected using past accident data and data collected ina behavior observation room developed by the authors. Finally, the significance of the infant behavior simulation was
described.
Further development of the proposed system will involvethe collection of accident data, expansion of the database,the incremental addition of physiological and other factors
to the internal factor, and experimental evaluation of the performance of the simulation.

Acknowledgments
The authors wish to thank Dr. Tatsuhiro Yamanaka at the
Ryokuen Children’s Clinic in Japan for providing injury accident data from over 200 cases. In addition, the authors
would like to thank Dr. Altion Simo at the Digital Human
Research Center at the National Institute of Advanced Industrial Science and Technology (AIST) for technical support
in developing the visualization system of the infant behavior simulator. Finally, the authors would like to thank Dr.
Jun Kohyama at Tokyo Kita Shakai Hoken Hospital in Japanfor providing useful information on infant physiology. This
study was funded in part by a Grant-in-Aid from the Secom
Science and Technology Foundation and by a Sasakawa Scientific Research Grant from the Japan Science Society (No.
16-322).

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[3] The Japanese Society of Child Health, Japanese Edition
DENVER II, The Japanese Child Medical Press, 2003
[4] H. Soubhi, P. Raina, D. Kohen, ”Effects of Neighbourhood, Family, and Child Behaviour on Childhood Injury in Canada,” Human Resources Development Canada, 2001 (which can be obtained fromhttp://www11.sdc.gc.ca/en/cs/sp/arb/publications/research/2001-000067/iw-01-1-6e.pdf)[5] U. Hansmann, L. Merk, M.S. Nicklous, T. Stober, Pervasive Computing Handbook. The Mobile World, SpringerVerlag Telos, 2001
[6] J. Fraden, Handbook of Modern Sensors: Physics, Designs, and Applications, AIP Press, 2003
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Kanade, M. Kakikura, ”3D Ultrasonic Tagging System
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