Research into
the mouthing
behaviour of
children up
to 5 years old.
Consumer and Competition Policy Directorate
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Research commissioned by the Consumer and Competition Policy Directorate, DTI.
Department of Trade and Industry
1 Victoria Street
London
SW1H 0ET
Carried out under contract by:
Dr Beverley Norris
Stuart Smith
Institute for Occupational Ergonomics
School of Mechanical, Materials, Manufacturing Engineering and Management
University of Nottingham
University Park, Nottingham, NG7 2RD
Tel: 0115 9514039 Fax: 0115 9514000
July 2002
URN 02/748
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SUMMARY 1
CHAPTER 1. Design of the research 2
1.1 Aims of this research 2
1.2 Data Collection 2
1.3 Experimental design 3
CHAPTER 2. Methodology 5

CHAPTER 6. Discussion 33
6.1 Validity and reliability of the study 33
6.2 Mouthing times 33
6.2.1 Mean and maximum mouthing times 33
6.2.2 What is mouthed 34
6.2.3 How items are mouthed 34
CHAPTER 7. Implications 36
7.1 Why children mouth 36
7.2 Overview of legislation and standards 36
7.3 Accident statistics on mechanical hazards 37
7.4 Mouthing times 38
7.5 Items mouthed 38
7.6 Hazards from items mouthed in this study 39
7.7 Reducing accident levels 43
7.7.1 Toys 43
7.7.2 Other objects 44
7.8 Using product features to deter mouthing 44
CHAPTER 8. Conclusions 45
CHAPTER 9. Recommendations 47
9.1 Toys 47
9.2 Other objects 47
CHAPTER 10. References 49
Appendix A: Observation recording form 50
Appendix B: Toy and objects details sheet 51
Appendix C: Child’s daily routine form 52
Appendix D: Questionnaire 53
Appendix E: Pictures illustrating mouthing behaviours 56
Appendix F: Examples of Toy Categories 57
Appendix G: Examples of "other objects" categories 69
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it is imperative that the environment in which the data are gathered is as unaffected by the
observation as possible. This means that the child should be surrounded by things that they are
used to and know. For this reason, the research by Groot et al (1998) and Juberg et al (2001) both
rely on data being recorded by the parent(s) of each child using a diary format. The child is
obviously used to the presence of their parent and so natural behaviour may be assumed. The
use of a structured formal diary recording system serves to control the type of information that
the parent is recording and therefore provides a level of validity and reliability to the research.
Greater levels of reliability would possibly be obtained through the use of trained researchers
observing the child in their home environment, as the observer is trained to record certain types
of behaviour consistently, and so providing good repeatability of observation. The same is true
for the use of video recording equipment, where very short behaviours can be reliably recorded.
However, it is likely that a child will be very aware of a video camera and being filmed, and this
could lead to a change in behaviour. Likewise, the presence of a stranger in the home is likely to
alter the behaviour of the child being observed to a greater or lesser extent, so while the
reliability of the data may be high, the circumstances are less "realistic" and lower the validity of
the data. Another problem with video recording is that young children are often on the move,
which would make capturing every behaviour extremely difficult. For these reasons this research
used parents/carers as observers, to ensure children’s mouthing behaviour, and behaviour
generally, were as natural as possible to ensure high data validity.
Observations were carried out at home rather than nurseries or childcare establishments as the
home environment has a vast range of items that are accessible to children, not all of which are
intended for use by them. This is a worst case scenario but also realistic compared to more sterile
environments such as playgroups and nurseries where the contents of rooms are very carefully
and rigidly controlled.
Because of the factors mentioned above it was felt that an examination of the reliability of
parents as observers should be carried out. This has not been investigated by prior studies
which have also used parents as observers. A comparison of parent and trained observer data
collection was carried out on a sample of 25 children. Information on this validation part of the
research may be found in Section 5 of this report.
Page 4

• what was mouthed
• which room of the house the observation was undertaken in
• other people present in the room
• whether the child was feeling unusually ill or tired during the observation
• how long it had been since the child last ate and slept
• what the child was doing during the observation.
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Information gathered over the whole study for each participant also included:
• details of the child’s physical and psychological development
• details of the child’s family (e.g. size, type of house lived in, social class)
• details of the time the child spent outside of the family home in a care environment
(e.g. a nursery, playgroup)
• details of toys mouthed by each child, part of toy mouthed and what each part mouthed
was made of
• details of what other objects were mouthed and what they were made of
• details of the child’s daily routine for the first and last days that they were observed i.e. what
time they got up and went to bed, and time spent eating and sleeping during the day.
The questionnaires and forms used to gather these data are presented in Appendices A, B, C and D.
Page 6
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Page 7
Chapter 2
Methodology
2.1 DEVELOPMENT OF MATERIALS
2.1.1 Pre-pilot trials
The use of a diary type observation recording system requires that the forms for recording
behaviour are simple and intuitive to complete. For this reason, a pre-pilot stage was undertaken.
Several alternative observation recording forms were produced and trialed in a local day nursery
by members of the Product Safety and Testing Group (PSTG) trained in observation protocols. For
the purposes of this stage, a single child was observed by both members of the PSTG for a

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2.2 OBSERVATION PROTOCOLS
2.2.1 Timing of mouthing behaviours
Participants in the research were each provided with a stopwatch for timing the duration of
mouthing events. They were not required to start, stop and reset the watch each time an event
occurred. Instead, the stopwatch was started at the beginning of the session and not stopped
until the 15 minutes was over. When the behaviour began, i.e. when the item first entered the
mouth, the time on the stopwatch was recorded on the observation form (to the nearest second),
and when that particular behaviour finished the time was again noted. This enabled a quicker
and more accurate time map of the child’s behaviour to be produced than by starting and
stopping the watch for each behaviour, especially for very short time behaviours.
2.2.2 Classifying what was mouthed
Products/items mouthed were classified into four categories: a dummy/soother, fingers,
toys, and other objects. The "fingers" category includes any part of the body of the child or of
another person, and whether an item was classified as a toy or other object was decided upon
by the observer.
2.2.3 Classifying the type of mouthing behaviour
Mouthing behaviour was classified into three categories. The instructions given to observers on
how to classify behaviour were as follows:
• Licking/lip touching. This is where the item is placed to the front of the mouth, without
actually entering into the mouth. The child may be actually licking an object, or may be
touching the object to their lips. The time recorded should be from when the object first
touches the child’s mouth to when the object is no longer in contact with the mouth. If a
child is licking an object it may be difficult to record because of the short time period
involved. In this case note the time when the object is put close to the mouth to be licked,
and then taken away from the mouth
• Sucking/trying to bite. The item is put directly into the mouth of the child. The child may
be sucking, holding the object in their mouth or trying to bite (gumming) the object
• Biting or chewing. The item is directly in the mouth of the child. It is clear that the child is
biting or chewing on it.

Age group
1-3 months
3-6 months
6-9 months
9-12 months
12-15 months
15-18 months
18-21 months
21-24 months
2 years
3 years
4 years
5 years
Number of boys
3
7
6
6
5
5
11
6
18
13
17
14
Number of girls
6
7
9

none
creche
playgroup
relative / friend
childminder
nursery
Day one
none
creche
playgroup
relative / friend
childminder
nursery
Day two
none
creche
playgroup
relative / friend
childminder
nursery
Day three
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Page 11
Age group
1-3 months
3-6 months
6-9 months
9-12 months
12-15 months
15-18 months

9:40
9:30
Maximum
13:30
12:48
11:50
11:23
11:05
12:42
12:15
13:39
13:20
13:50
14:10
14:00
Figure 1: Childcare arrangements, by day, for children observed in the study.
As the number of observation days increases the number of children going to some form of
childcare decreases. Nursery is the most popular form of childcare.
Information was gathered on how much time during a typical normal day the child would have
available to spend mouthing, that is, time not spent sleeping or eating.
Table 2 presents the mean, minimum and maximum times available to mouth for each age group
none
creche
playgroup
relative / friend
childminder
nursery
Day five
none
creche

group. For example, for 3-6 months olds, only 4 subjects may have actually mouthed on a
dummy/soother but the total estimate of daily mouthing on a dummy/soother for that age was
divided by the total number of subjects in that age group (14) to give the mean value of daily
mouthing time that could be expected across that age group generally.
Because of the skewed
2
nature of the raw data used to produce these estimates care should be
taken if using mean estimated daily mouthing values for the purposes of safety. This is because
the mean value may not reflect the true average or middle value of the sample for each age
group, depending on the degree to which the data are skewed.
4.1 ESTIMATED DAILY MOUTHING TIME BY ITEM MOUTHED
Figure 2 presents the mean estimated daily mouthing time for males and females combined for
each item mouthed (in hours:minutes:seconds). Each mean behaviour is the average time that a
child in each age group could be expected to mouth a given item over a normal day. Mean total
daily mouthing time is the time that any child could be expected to mouth, on anything, on
average over a normal day, and is the sum of mean mouthing time on all items for each age group.
1
The Kruskal-Wallis test is a non-parametric statistical test used to determine whether values of scores for three or more groups are significantly different, in
this case we have four groups, i.e. those observed between waking and 11am, between 11am and 2pm, between 2pm and 6pm, and 6pm until bedtime.
2
The observed data have a skewed distribution because in general a high percentage of observed mouthing behaviours for each age group were very short in
nature (i.e. only a few seconds), with only a small percentage being observed with duration of between 1 and 15 minutes.
Page 12
Chapter 4
Results
* time available to mouth per day
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Page 13
Table 3 presents the mean and maximum estimated daily mouthing data, for males and females
combined. Data shown for males and females combined as a Mann-Whitney

18-21
21-24
2
3
4
5
Age category
Mean mouthing time
Dummy / Soothe
r
Fingers
Toys
Other objects
Not recorded
Total
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Table 3: Estimated mean and maximum daily mouthing time for all items mouthed
(hours:minutes:seconds).
Table 4: Estimated mean and daily mouthing time on all items mouthed (hours:minutes:seconds).
Page 14
Item mouthed
Dummy/
Soother
Fingers
Toys
Other
Objects
Not
Recorded
Mean

15 -1 8
months
18 -21
months
21-2 4
months
2
years
3
years
4
years
5
years
Item mouthed
Total
estimated
mouthing on
all items
Mean
Max
Age Group
1- 3
months
3-6
months
6-9
months
9-12
months

decreases.
4.2 ESTIMATES OF DAILY MOUTHING TIMES ACCORDING TO WHAT WAS MOUTHED AND HOW
Mouthing time is presented for mouthing on all items and also separately for each category
of item mouthed (for males and females combined), in the following sections:
4.2.1 All items
4.2.2 Dummy/soother
4.2.3 Fingers (and other parts of the body)
4.2.4 Toys
4.2.5 Other objects
4.2.6 Item not recorded
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
1-3
3-6
6-9
9-12
12-15
15-18
18-21
21-24
2
3
4
5

3-6
6-9
9-12
12-15
15-18
18-21
21-24
2
3
4
5
Age category
Mean mouthing time
lick, suck and bit
e
suck and bite
lick and bite
lick and suck
bite
suck
lick
0:00:00
0:10:00
0:20:00
0:30:00
0:40:00
0:50:00
1:00:00
1:10:00
1:20:00

Suck
Lick and
Bite
Mean
Max
Mean
Max
Mean
Max
Mean
Max
Mean
Max
Age Group
1- 3
months
3-6
months
6-9
months
9-12
months
12-15
months
15 -1 8
months
18 -21
months
21-2 4
months

- - - - 0:04:55 - 0:01:58 0:03:13 0:00:44 0:01:11 - -
- - - - 1:18:32 - 0:31:23 0:38:36 0:28:49 0:36:43 - -
- - - - - - - - 0:00:37 - - -
- - - - - - - - 0:24:15 - - -
0:01:36 0:00:47 0:02:52 - 0:00:22 0:05:00 0:04:00 - 0:02:01 - - -
0:14:28 0:05:37 0:34:14 - 0:05:22 0:45:26 0:32:25 - 0:32:00 - - -
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4.2.3 Fingers
Figure 6 shows how fingers were mouthed at each age group, and Table 6 presents the estimated
daily mouthing data shown in Figure 6.
Figure 6: Estimated mean daily mouthing time for fingers according to how they are mouthed
(hours:minutes:seconds).
0:00:00
0:05:00
0:10:00
0:15:00
0:20:00
0:25:00
0:30:00
0:35:00
0:40:00
0:45:00
0:50:00
1-3
3-6
6-9
9-12
12-15
15-18
18-21

Mean
Max
Mean
Max
Mean
Max
Mean
Max
Age Group
1- 3
months
3-6
months
6-9
months
9-12
months
12-15
months
15 -1 8
months
18 -21
months
21-2 4
months
2
years
3
years
4

0:00:22 0:03:07 0:02:40 1:38:42 0:00:09 0:05:14 0:05:23 0:00:18 0:03:19 0:04:20 0:00:07 0:12:27
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4.2.4 Toys
Figure 7 shows how toys were mouthed at each age group, and Table 7 presents the estimated
daily mouthing data shown in Figure 7.
Figure 7: Estimated mean daily mouthing time for toys according to how they are mouthed
(hours:minutes:seconds).
Page 20
0:00:00
0:05:00
0:10:00
0:15:00
0:20:00
0:25:00
0:30:00
0:35:00
0:40:00
0:45:00
1-3
3-6
6-9
9-12
12-15
15-18
18-21
21-24
2
3
4
5

Max
Age Group
1- 3
months
3-6
months
6-9
months
9-12
months
12-15
months
15 -1 8
months
18 -21
months
21-2 4
months
2
years
3
years
4
years
5
years
Mean
Max
Suck and
Bite