Child Development, xxxxx 2012, Volume 00, Number 0, Pages 1–13
Enhanced Handling and Positioning in Early Infancy Advances
Development Throughout the First Year
Michele A. Lobo and James C. Galloway
The University of Delaware
Behaviors emerge, in part, from the interplay of infant abilities and caregiver–infant interactions. Crosscultural and developmental studies suggest caregiver handling and positioning influence infant development.
In this prospective, longitudinal study, the effects of 3 weeks of enhanced handling and positioning experiences
provided to 14 infants versus control experiences provided to 14 infants at 2 months of age were assessed
with follow-up through 15 months of age. Behaviors in prone were immediately advanced. Short-term
advancements occurred in multiple behaviors, including prone, head control, reaching, and sitting behaviors.
Longer term advancements, up to 12 months after the experience period, occurred in object transfer, crawling
and walking behaviors. This suggests broad and long-lasting changes can arise via brief periods of change in
caregiver–infant interactions.
The role of daily experience in the typical development of early behaviors is of interest to several
disciplines. For developmental psychology and
early education, studies that quantify the effects of
daily experiences provide an empirical test of key
theoretical principles of how infants gain the foundational skills for increasingly complex behaviors.
For example, this study tests the notion of embodied development, which states that developmental
abilities do not emerge de novo but emerge from a
rich history of exploration and daily interactions
between caregivers, young infants, and the physical environment (Adolph & Berger, 2006; Lockman, 2001). For pediatric rehabilitation, studies
that quantify the effect of caregiver–infant interactions provide an important foundation for new
assessment and intervention strategies and highlight the potential benefits of family-centered interventions (Bamm & Rosenbaum, 2008). The general
purpose of this project was to determine if a relatively short period of caregiver–infant interactions
would impact longer term changes in development.
Specifically, we aimed to determine the developmental consequences of a 3-week caregiver-provided enhanced handling and positioning program.
This research was supported in part by fellowships from The
University of Delaware and The Foundation for Physical Therapy.
Correspondence concerning this article should be addressed to
Michele A. Lobo, Department of Physical Therapy, 329 McKinly
Building, The University of Delaware, Newark, DE 19716. Electronic mail may be sent to malobo@udel.edu.
These activities were ‘‘enhanced’’ because they
involved behaviors that are not typical of daily life
for young infants born into Western cultures. These
behaviors included supported sitting and standing,
encouragement of independent head and trunk
control, and emphasis on prone positioning (Kuo,
Liao, Chen, Hsieh, & Hwang, 2008). Our previous
research suggested that enhancing caregiver–infant
interactions immediately advances the emergence
of reaching, as well as object exploration and problem-solving development weeks to months after
stopping the enhanced experiences (Lobo & Galloway, 2008; Lobo, Galloway, & Savelsbergh, 2004).
The current study focused on quantifying even
longer term changes through the onset of walking
around 1 year of age. This study is the first to use a
prospective experimental design to assess the effects
of early, prescribed changes in caregiver handling
and positioning practices on infant motor development into the 2nd year of life. We hypothesized
2-month-old infants provided enhanced handling
and positioning experiences would display more
advanced development throughout the 1st year
of life.
Our hypothesis is supported by cross-cultural
studies suggesting that differences in handling and
positioning can affect infant development. ‘‘Handling’’ is those behaviors that occur when caregivers
2012 The Authors
Child Development 2012 Society for Research in Child Development, Inc.
All rights reserved. 0009-3920/2012/xxxx-xxxx
DOI: 10.1111/j.1467-8624.2012.01772.x
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Lobo and Galloway
are in physical contact with young infants. Differences in handling practices across cultures have been
associated with differences in the development of
adaptive behaviors, motor behaviors, early communication, and cognitive development (Adolph,
Karasik, & Tamis-LeMonda, 2010; Bril & Sabatier,
1986; Hopkins & Westra, 1988). For instance, in
areas of Kenya, Nigeria, and West India, formal handling techniques to encourage sitting and walking
from birth have resulted in infants sitting and
walking months earlier than those in Western cultures. Non-Western caregivers using similar formal
handling techniques have infants with better head
control at 1 month and advanced sitting and standing at 6 months of age compared to infants born to
mothers not using such practices (Hopkins & Westra,
1989).
Young, immobile infants also spend considerable time being placed in positions by caregivers.
Descriptive studies suggest that greater experience
in multiple positions in the months after birth is
associated with better development in the 1st year
for healthy infants and those born preterm and at
risk for delays (Fetters & Huang, 2007). Reduced
experience in the months after birth in the prone
position, a position that is especially challenging
for young infants and that most caregivers avoid
or utilize very little, is associated with delayed
development in certain skills in the 1st year of life
(Kuo et al., 2008; Majnemer, 2007). Therefore,
theoretical and cross-cultural work suggests that
caregivers facilitate infants’ development through
their everyday handling and positioning interactions. This prospective, longitudinal, multiplegroup study specifically tested this proposal. Our
goal was to build upon these findings from across
cultures and within Western cultures to create an
enhanced handling and positioning program
aimed at advancing future development.
Process by Which Handling and Positioning Were
Expected to Affect Developmental Change
We expected a relatively brief period of enhanced
handling and positioning would have longer
lasting effects for two reasons. First, the altered
handling and positioning activities were expected
to advance infants’ foundational abilities that are
developmentally linked to future skills. For
instance, being placed in a range of positions
allows infants to experience a variety of possibilities for action, views of the world, levels of arousal
and social interaction, and postural and strength
requirements (Fogel, Messinger, Dickson, & Hsu,
1999). These opportunities were expected to lead
to corresponding changes in infants’ potential to
perceive, act, and attend within their world. Second, we expected caregivers would adapt to their
infants’ emerging abilities and continue advancing
their interactions even outside of and after the
home experience period. A cycle would occur in
which changes in caregivers or infants would in
turn create change in the other (Bronfenbrenner,
1979). For instance, our work and others’ suggest
that once caregivers observe their infants attempting to reach for objects, they begin to present
objects to infants more often within reach so
infants have greater opportunities daily for object
exploration (Fogel, 1997; Lobo & Galloway, 2008;
Reed & Bril, 1996). This ongoing cycle of change
supports the emergence of novel behaviors in
development and the maintenance of gains when
development is advanced through early intervention (Gottlieb, 1983; Ramey & Ramey, 1998). The
present study aimed to accelerate this cycle by
educating caregivers to use handling and positioning techniques to facilitate developmental advancements that were expected to continue well into the
future.
We expected the handling and positioning experiences to have broad developmental effects
because they aimed at enhancing early perceptualmotor experiences across a variety of postures and
activities. Some literature suggests that the effects
of early experiences are specific. For instance, taskspecific activities focused on advancing target
skills, like sitting or stepping, can advance the onset
of those target skills (Vereijken & Thelen, 1997;
Zelazo, Zelazo, Cohen, & Zelazo, 1993). Similarly,
perception of traversibility of slopes has been demonstrated to be dependent upon specific experience
with each mode of locomotion, such as creeping on
hands and knees and walking (Adolph, TamisLeMonda, Ishak, Karasik, & Lobo, 2008). On the
contrary, other studies have suggested that the
effects of experiences can be much broader. For
instance, sitting ability has been shown to advance
knowledge about object properties (Soska, Adolph,
& Johnson, 2010). Early experiences to advance
reach onset also advance future object exploration
and means–end problem-solving ability (Lobo &
Galloway, 2008). And early experiences in prone
advance the future ability to crawl on hands and
knees (Adolph, Vereijken, & Denny, 1998). The
present study aimed to utilize a variety of early
experiences in order to advance the development of
those skills practiced as well as to advance the
development of future related skills.
Handling and Positioning Advance Development
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Method
Participants
Twenty-eight families with infants born full-term
were recruited from the local community at
2 months of age. Inclusion criteria were typical
development and no medical diagnoses. Twentysix of the infants were Caucasian and 2 were
African American. Caregivers provided informed
consent. Three additional families were excluded
from the study because they did not meet the minimum experience performance criterion (see below
for details).
Experience Groups
Infants were randomly assigned to either the
social experience (control) group or the handling
and positioning experience (experimental) group.
Infants were matched for gender so each group had
seven males and seven females.
Experiences were provided to infants by caregivers 15 min daily the first 3 weeks of the 60-week
study when infants were in an awake and alert
state. Caregivers were informed they could perform
the experiences in shorter segments throughout the
day if necessary to ensure infants remained in a
positive behavioral state during the activities. Caregivers received an illustrated manual and training
from an experimenter at the first study visit (see
Figure 1). They were given a diary to chronicle the
frequency, duration, and content of their sessions.
There was a minimum experience performance
criterion of 60% of the days for inclusion in the
study. Each participant’s diary was examined after
the prescribed home experience period and anyone
not meeting the 60% criterion was excluded from
the study at that point. The same experimenter, a
licensed pediatric physical therapist, trained all
families and conducted the visits.
At the second study visit caregivers were offered
the opportunity to ask questions, were asked to
demonstrate the home experiences without referring to the manual, and were offered any suggestions to improve the provision of the activities if
they deviated from the instructions. After the end
of the experience period (third study visit), caregivers were no longer required to perform the activities with their infants.
Social Experience (Control)
Caregivers in the control group were asked to
place their infants in supine and engage them in
Figure 1. Time line showing the schedule of home experience,
assessments, and home visits in relation to the ages of
participants.
face-to-face interaction for 15 min daily (see
Figure 2a for related image and online supporting
information Appendix S1 for more detail). The aim
of these experiences was to control for the social
interaction and associated general movements that
infants in the experimental group would receive.
Therefore, the social experiences chosen were typical for this developmental period and incorporated
the social and supine general movement components of the experimental experiences. Caregivers
were asked to use minimal physical interaction and
no objects during these interactions and to use their
face and voice to encourage infants to attend to
them. We did not choose more advanced social
experiences because it was likely that such experiences would accelerate development in other ways.
Handling and Positioning Experience (Experimental)
Caregivers in the experimental group were asked
to perform advanced handling and positioning
activities with their infants 15 min daily. The specific activities involved caregivers encouraging and
assisting infants: (a) by placing them in prone on
the floor or caregiver while encouraging them to
push up to lift their head, (b) by pulling them up
and lowering them down slowly between sitting
and supine while assisting them to keep their head
in line with their body, (c) by supporting them in
sitting and standing while swaying them slowly in
different directions while encouraging them to
weight bear and to reorient their body upright with
respect to gravity, and (d) by moving their hands to
midline for play to encourage a shift from lateral to
more midline arm placement (see Figure 2b–g for
related images and online supporting information
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Lobo and Galloway
a
b
d
c
e
f
g
Figure 2. Caregivers in the social experience (control) group (a) were asked to place their infants in supine and engage them in face-toface interaction without objects for 15 min daily. Caregivers in the handling and positioning experience (experimental) group were
asked to perform activities for 15 min daily to encourage and assist pushing up in prone (b, c), pulling up and lowering down between
supine and sitting (d), maintaining head and upper body control in assisted sitting and standing (e, f), and moving hands to midline (g).
Appendix S2 for more detail). These activities provided enhanced perceptual-motor experience across
positions in order to promote abilities including
strength, postural control, and midline hand behavior. These activities also involved a fair amount of
social interaction between caregivers and infants.
Procedure
Assessments in the Home
The same experimenter, a licensed pediatric
physical therapist, visited families in their homes for
6 visits across the first 3 months of the study. The
average age of infants at each visit was 9, 10.5, 12,
15, 18, and 21 weeks of age (see Figure 1 for assessment schedule). There were no differences in the
ages of infants in each group at the start of the study
or at subsequent visits (age in weeks Visit 1: control
8.7 ± 0.9, experimental 8.9 ± 0.7; Visit 2: control 10.3
± 0.9, experimental 10.6 ± 0.8; Visit 3: control 11.8 ±
0.8, experimental 11.9 ± 0.7; Visit 4: control 14.8 ±
0.7, experimental 14.9 ± 0.9; Visit 5: control 17.9 ± 0.8,
experimental 17.9 ± 0.9; Visit 6: control 20.6 ± 0.8,
experimental 20.8 ± 1.0). Visits were documented
via video recordings so coders blind to group
assignment and not present for visits could code the
assessments described below. The visits were conducted when infants were in an awake and alert
state. The first and second visits also included training activities for caregivers as aforementioned.
Alberta Infant Motor Scale (AIMS). At every home
visit, infants’ general motor ability was assessed
using the AIMS. This is a valid and reliable assessment tool that compares young infants’ motor performance with a normative sample. It consists of
observation of infants’ weight bearing, posture, and
antigravity movement in four positions ⁄ subscales:
supine, prone, sitting, and standing (Piper, Pinnell,
Darrah, Maguire, & Byrne, 1992). Each subscale
consists of a series of behaviors infants may be
observed to progress through developmentally. For
instance, in prone, infants may progress through
pushing up on their arms with their elbows behind
their shoulders, then with their elbows in line with
their shoulders, and then may demonstrate the ability to lift their heads higher and shift their weight.
Infants receive a score of 1 for behaviors they are
Handling and Positioning Advance Development
observed performing and a 0 for more advanced
items they were not observed performing. Therefore, each point received reflects an infant’s ability
to behave at a new level within each position.
Reaching. At every home visit, infants’ reaching
ability was assessed in supine and seated in a custom chair. In each position, infants were given one
3-min trial to interact with a stationary, midline toy
held an arm’s length away at chest level.
Caregiver Questionnaire
Caregivers were provided written questionnaires
at the start of the study and at the final home visit
at 5 months of age. The questionnaires assessed
infants’ sleeping position and if and how caregivers
reportedly changed the ways they interacted with
their infants as a result of participation in this study
(see online supporting information Appendix S2).
Follow-up Developmental Assessment
From the end of the home assessments at
5 months of age until the onset of independent
walking between 10 and 15 months of age, infants
were followed using a reliable and valid Parent
Milestone Report Form (Adolph, Robinson, Young,
& Gill-Alvarez, 2008; Bodnarchuk & Eaton, 2004).
Caregivers were asked to track their infant’s development on behaviors from reaching through creeping on hands and knees and walking. Once weekly
they documented whether they observed their
infant performing each of the behaviors. Then at
the end of each month, an experimenter blind to
group assignment collected these data from the
caregiver by phone and recorded them.
Variables
Assessments in the Home
Alberta Infant Motor Scale. A trained experimenter
who did not perform the home visits and was blind
to group assignment and the details of the study
scored the AIMS assessments from video. A second
scorer, also blind to group assignment and not present at visits, scored 20% of the assessments to ensure
interrater reliability with the primary scorer. The
number of item scores agreed and disagreed on was
determined and the percentage of reliability was
calculated using the equation: [agreed ⁄ (agreed + disagreed)] · 100. Interrater reliability between the two
scorers was 94%. Infants received a score for each
subscale (supine, prone, sitting, and standing) as well
5
as a total score (sum of the four subscale scores). We
analyzed scores at Visit 1 to ensure groups were similar at the start of the study. We analyzed changes in
AIMS scores for infants in each group during the 3week experience period (2–3 months of age) and
throughout the home assessment period (through
5 months of age) to assess the immediate and shortterm effects of the home experiences.
Reaching. Two trained experimenters blind to
group assignment coded the number of times
infants contacted the midline object from the
reaching assessment videos. Each time the infant’s
hand came in contact with the object, a contact
was coded. From these data, we calculated the
visit of reach onset for each infant, or the first visit
when the infant contacted the midline object more
than 10 times total (total contacts supine and
seated in the chair) and the number of object contacts for all subsequent visits remained greater
than this value.
Coding reliability was assessed for 20% of the
coded data across age using the equation described
above. Intrarater reliabilities were 95% and 96% for
each coder. Interrater reliability was 92% between
coders.
Caregiver Questionnaire
Caregiver responses were categorized for statistical analyses by two experimenters blind to group
assignment. Interrater agreement for categorization
was Kappa = 1.00 (p < .001). Sleeping position was
categorized into supine, prone, or sidelying. Study
participation was categorized as either having an
effect or having no effect on caregiver–infant interactions. For those who reported participation did
affect their interactions, the ways in which their
interactions were affected were categorized as
increased social interaction (responses such as
‘‘looking,’’ ‘‘attention,’’ or ‘‘talking’’), increased handling and positioning interaction (responses such as
‘‘postures,’’ ‘‘strength,’’ or ‘‘continued with experience activities’’), or increased play with objects
(responses such as ‘‘toys,’’ ‘‘reach,’’ or ‘‘hold’’). All
responses fell into one of these three categories.
Follow-up Developmental Assessment
The weekly milestone tracking was used to determine the week of each milestone’s onset in relation
to the week the infant had his or her first study visit.
When infants were first observed performing a
behavior 3 weeks consecutively, the onset of the
behavior was defined as the first of these weeks. For
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Lobo and Galloway
instance, if an infant was observed by his or her
caregiver transferring objects from hand to hand at
15, 16, and 17 weeks after the week of the infant’s
first visit, the onset of this behavior was recorded as
happening at 15 weeks after the first visit. To provide readers with a better perspective of developmental time, these results are reported both in terms
of weeks from the first visit as well in terms of
infants’ ages in months.
Data Analysis
Mann–Whitney U nonparametric tests were used
to compare the two groups for all variables. Median
followed by minimum and maximum values in
parentheses and effect size using Cohen’s correlation coefficient (r) are reported for all comparisons,
with r = 0.10 representing a small effect, r = 0.30
representing a medium effect, and r = 0.50 representing a large effect (Cohen, 1992). One-tailed tests
were utilized for variables we hypothesized would
be different as a result of the experiences, such as
change in AIMS score after enhanced experience.
Two-tailed tests were used for the remainder of the
variables, such as age at the first visit. Only results
with significance values £ 0.05 are reported. To better describe these significant group changes, we
also report individual counts of behaviors. To test
the robustness of the findings, all analyses were
also performed using parametric independent sample t tests with Levene’s test for equality of variances. The parametric and nonparametric findings
were consistent but the nonparametric findings are
reported here because many of the variables are
ordinal and our sample sizes are modest.
sleep supine compared to infants who sleep prone
(Davis, Moon, Sachs, & Ottolini, 1998).
At the start of the study, the control and experimental groups had similar total AIMS scores:control Mdn 9 (8, 13), experimental Mdn 9 (7, 13); and
similar scores for the supine:control Mdn 3 (2, 5),
experimental Mdn 3 (2, 5); sitting:control Mdn 1 (1,
2), experimental Mdn 1 (1, 2); and standing:control
Mdn 2 (1, 2), experimental Mdn 2 (2, 2); AIMS
subscales (total U = 60.50, ns, r = )0.35; supine
U = 92.00, ns, r = )0.06; sitting U = 98.00, ns,
r = .00; standing U = 77.00, ns, r = )0.34). Control
infants did have better prone subscale scores at this
visit, about 1 point higher:control Mdn 3 (2, 6),
experimental Mdn 2 (1, 6) (U = 53.50, p £ .05,
r = )0.41). Because the difference was in favor of
our control group and we believed our experiences
would advance development for the experimental
group beyond this difference, this small difference
at the start of the study was acceptable. Infants’
median total AIMS scores were at the 50th percentile for both groups at the start of the study.
Groups Had Similar Amounts of Home Experience
During the 3-week home experience period, both
groups had a similar number of days of experience:control Mdn 17.5 (14, 25), experimental Mdn
18.5 (17, 23) days (U = 63.00, ns, r = )0.31) and similar total minutes of experience:control Mdn 267.5
(210, 795), experimental Mdn 268 (182.5, 403) total
minutes; control Mdn 15 (13.4, 31.8), experimental
Mdn 13.8 (10.3, 19.19) min ⁄ day (U = 81.50, ns,
r = )0.14).
Immediate Effects of the Experiences: Advancements in
Prone Abilities
Results
Groups Began the Study at a Similar Age and
Developmental Level
Infants were similar at the start of the study. All
infants were born full-term and there was no difference in weight at birth between groups. Infants in
each group started the study at the same age:control Mdn 8.4 (7.7, 11.0), experimental Mdn 8.7 (8.1,
11.2) weeks old, U = 72.50, ns, r = )0.22. There was
no reported difference in sleeping position of
infants (U = 82.50, ns, r = )0.22). The majority of
infants in each group slept in supine. Sleep position
differences between groups could have been an
important confound because motor development in
the 1st year of life may be delayed in infants who
At the end of the 3-week home experience period
when infants were 3 months old, infants in the
experimental group were already making developmental advances compared to control infants (see
Figure 3). From 2 to 3 months of age they had
greater increases in their AIMS prone subscale
scores:control Mdn 1 (0, 4), experimental Mdn 2
(0, 5) points change (U = 47.50, p £ .01, r = )0.45).
This manifested from greater advancements in their
ability to push up on their forearms and extended
arms, to shift their weight for early mobility, and to
raise one arm to reach for objects and people in the
prone position. After the home experience, control
infants’ median total AIMS score was at the 65th
percentile, while experimental infants’ median
score increased to the 80th percentile.
Handling and Positioning Advance Development
Figure 3. Immediate changes in development for each group
during the experience period represented by changes in total
and subscale scores on the Alberta Infant Motor Scale (AIMS).
Note. The time frame represents 3 weeks between 2 and
3 months of age in this box plot.
*p £ .05.
Short-Term Effects of the Experiences: Advancements
in Global Motor Abilities, Hand Movement, Object
Interaction, and Head Righting
After the 3-week home experience period, caregivers were no longer asked to perform the home
activities, yet experimental infants continued to
demonstrate advancements. Specifically, from 3 to
5 months of age, experimental infants demonstrated
advanced midline hand movement ability, object
interaction abilities, head righting abilities, and global motor development. They began to rest their
hands in midline rather than lateral in supine, an
item on the AIMS, earlier than control infants (at
3 months: 8 of 14 control infants; 12 of 14 experimental infants, U = 70.00, p £ .05, r = )0.31; at
4 months: 10 of 14 control infants; all 14 experimental infants, U = 70.00, p £ .05, r = )0.40). Next, they
reached for objects earlier in the reaching assessment:control Mdn 18 (12, 21), experimental Mdn
13.5 (10.5, 21) weeks of age (U = 59.00, p £ .05,
r = )0.34). Control infants were reaching in the
middle of the typical age expected (3–5 months of
age) by about 4.2 months of age, while experimental infants were reaching at the early end by about
3.1 months of age (Thelen, Corbetta, & Spencer,
1996). At the first visit no infants were reachers. At
the second and third visits (around 2.5 and then
3 months old), no control infants and 4 experimental infants were reachers (Visit 2: U = 28.00, p £ .05,
r = 0.4; Visit 3: U = 28.00, p £ .05, r = 0.4). At the
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fourth visit (around 3.75 months old), 6 control and
9 experimental infants were reachers. At the fifth
visit (around 4.5 months old), 10 control and 12
experimental infants were reachers. At the last
home visit (around 5.25 months old), 13 control
and all 14 experimental infants were reachers. After
reach onset, experimental infants were able to right
their heads earlier by keeping it in line with their
trunk when pulled by the hands from supine to sitting, another item on the AIMS (at 4 months: 5 of
14 control infants, 10 of 14 experimental infants,
U = 63.00, p £ .05, r = )0.35; at 5 months: 9 of 14
control infants, 13 of 14 experimental infants,
U = 70.00, p £ .05, r = )0.34).
Infants in the experimental group were making
greater global motor developmental advances compared to control infants (see Figure 4). Through
5 months of age they had greater increases in their
AIMS total scores, prone subscale scores, and
sitting subscale scores—points change total: control
Mdn 8 (5, 12), experimental Mdn 11 (8, 18)
(U = 45.50, p £ .01, r = )0.46); prone: control Mdn 3
(2, 6), experimental Mdn 5 (3, 9) (U = 42.50, p £ .01,
r = )0.45); sitting:control Mdn 2 (0, 4), experimental
Mdn 3 (1, 7) (U = 62.00, p £ .05, r = )0.34). At
5 months of age, control infants’ median total AIMS
scores were at the 30th percentile, while experimental infants’ scores were at the 50th percentile.
Figure 4. Short-term changes in development for each group
during the home assessment period represented by changes in
total and subscale scores on the Alberta Infant Motor Scale
(AIMS).
Note. The time frame represents 3 months from 2 to 5 months of
age in this box plot.
*p £ .05.
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Lobo and Galloway
Longer-Term Effects of the Experiences: Advancements
in Object Manipulation and Locomotor Abilities
In the 7–12 months following the 3-week home
experience period, experimental infants continued
to show important advances in object manipulation
and locomotion abilities (see Figure 5). Infants in the
experimental group transferred objects from one
hand to the other 2.5 weeks earlier, explored their
environment by creeping or crawling on their hands
and knees 5 weeks earlier, walked supported sideways holding on to furniture or forward holding on
to an adult’s hands 2.5 weeks earlier, and walked
alone less than 10 ft 6 weeks earlier—weeks from
the first study visit object transfer:control Mdn 15.5
(10, 24), experimental Mdn 13 (4, 18) (U = 57.50,
p £ .05, r = )0.35); creeping on hands and knees:
control Mdn 29 (16, 35), experimental Mdn 24 (11,
38) (U = 58.00, p £ .05, r = )0.30); walking with support: control Mdn 33 (28, 46), experimental Mdn 30.5
(24, 43) (U = 60.00, p £ .05, r = )0.33); walking independently: control Mdn 45 (37, 67), experimental
Mdn 39 (31, 55) (U = 57.50, p £ .05, r = )0.35).
Transferring objects from hand to hand typically
emerges between 5 and 6 months of age and was
defined in the parent report form as when the ‘‘baby
can pass a small toy, cookie, or other object from
hand to hand.’’ This behavior emerged in control
and experimental infants within the typical range at
5.5 months of age and 5.3 months of age, respec-
tively. Creeping on hands and knees typically
emerges around 8–10 months of age and was
defined in the parent report form as crawling more
than 10 ft using only the hands and knees for support, with the back straight, the knees under the
hips, and the elbows under the shoulders. This
behavior emerged for control infants within the typical range at 8.7 months of age and for experimental
infants a bit earlier at 7.5 months of age. Walking
with support typically emerges between 10 and
11 months of age and was defined in the parent
report form as the infant supporting his or her own
weight and taking several steps but receiving assistance to balance by holding furniture and stepping
sideways or holding an adults’ hands and stepping
forward. This behavior emerged for control infants
just before the typical range at 9.7 months of age and
for experimental infants a bit earlier at 9.1 months of
age. Walking independently typically emerges
around 12 months of age and was defined in the
parent report form as the infant taking at least one
step alone with each foot without the support of others or objects (Haywood & Getchell, 2009; Long &
Cintas, 1995; Piek, 2006). This behavior emerged for
control infants at the typical age of 12.4 months and
for experimental infants a bit earlier at 11 months.
The Experiences Elicited Different Changes in
Caregiver-Infant Interactions
A similar majority of caregivers in each group
reported on the parent questionnaire that participation in the study did affect the way they interacted
with their infants (12 of 14 control infants, all 14
experimental infants). However, the specific ways
caregivers reported their interactions were affected
were quite different between groups (U = 175.00,
p < .01, r = 0.78). Thirteen of the 14 experimental
caregivers reported that they handled or positioned
their infants differently. In contrast, 10 of the control caregivers who reported their interactions with
their infants were affected reported that they
played more socially with their infants. The remaining families in each group reported greater increase
in interest playing with toys.
Figure 5. Longer term changes in age of milestone emergence for
infants in each group based on the reaching assessment and
caregiver report form.
Note. Milestones represented are reaching for midline objects
(reach), transferring objects between the hands (transfer),
creeping on hands and knees (creep), walking with support
(walk sup), and walking independently (walk ind).
*p £ .05.
Discussion
Infants who received enhanced handling and positioning experiences at 2 months of age showed
advanced abilities that began immediately and continued through 12 months after the experiences.
Behaviors in prone were immediately advanced,
Handling and Positioning Advance Development
followed by advancements in prone, head control,
midline hand control, reaching, and sitting behaviors. Longer term advancements occurred in object
transfer, creeping on hands and knees, and walking
behaviors.
How did a relatively short period of advanced
experience lead to such lasting and widespread
advancements in infants’ motor abilities? How did
infants improve not only on tasks experienced,
such as hands to midline and head righting, but
also on other tasks, such as reaching and transferring objects? To answer these questions, we first
discuss the interrelation of the skills advanced. Second, we discuss some key changes in infants, caregivers, and caregiver–infant interactions that likely
created and maintained this advanced developmental trajectory.
Skills Advanced Share Common Thread
Infants in the experimental group were advanced
in skills ranging from floor play to object manipulation and locomotion. Although these skills may
at first glance seem very different, they all share
a common thread. These skills do not emerge de
novo but from a rich history of perceptual-motor
experience (Kamm, Thelen, & Jensen, 1990). All are
also important vehicles for exploration and the
development of embodied cognition (Adolph &
Berger, 2006; Lockman, 2001). Behavioral development in infancy can often be linked to previous
experience with seemingly unrelated activities. For
instance, a certain level of experience and control in
prone and supine precedes the onset of independent sitting (Green, Mulcahy, & Pountney, 1995).
Prone experience is connected to the development
of creeping on hands and knees as it allows infants
to coordinate the co-occurrences of head orienting,
reaching, and kicking (Goldfield, 1989). Therefore,
advancements in development so far after our
experience period ended were likely related to
experimental infants’ enriched perceptual-motor
history. We now discuss some mechanisms through
which these experiences may have advanced development.
Changes Within Infants
The likely consequence of experimental infants’
early experiences was enhanced priming of their
perception-action and cognitive systems. Below we
describe some ways experience may have advanced
the development of experimental infants’ perception-action and cognitive systems.
9
First, infants in the experimental group likely
developed advanced postural control. Postural
control is important for each of the skills we
measured and develops as a result of movement
and experience in a variety of positions (Bertenthal
& Von Hofsten, 1998; Chen, Metcalfe, Chang, Jeka,
& Clark, 2008). For instance, the postural control
required to manipulate objects develops, in part,
from earlier experiences maintaining balance in
reaction to perturbations from spontaneous arm
movements (Thelen & Spencer, 1998). The postural
control required to manipulate objects while sitting
or standing is not present when infants begin to
independently assume these positions but develops
through exploratory play in various positions (van
der Fits, Klip, van Eykern, & Hadders-Algra, 1999).
As experimental infants explored their perceptionaction possibilities across positions they likely constructed a range of complex anticipatory reactions
to maintain balance and body alignment (Metcalfe
& Clark, 2000).
Second, experimental infants may have physiologically primed their neuromuscular systems to be
better prepared for action. The experimental group
was exposed to various positions and movement
experiences that required head, trunk and limb
muscles to work against gravity, which is known to
increase muscular strength (Kleyweg, Vandermeche,
& Schmitz, 1991). Experiencing movements across
positions also likely taught them to coordinate
their muscular forces along with inertial forces
from distant joints and gravity to produce smooth,
functionally adaptive movements (Galloway &
Koshland, 2002). In addition, the neuromuscular
activity associated with the handling and positioning experiences may have guided the pruning and
strengthening of neuronal connections, the pruning
and strengthening of one neuronal innervation per
muscle fiber, and the development of the corticospinal system, all processes shaped by perceptionaction experience (Eyre, Taylor, Villagra, Smith, &
Miller, 2001; IJkema-Paassen & Gramsbergen, 2005;
Martin, Choy, Pullman, & Meng, 2004). Consequently, experimental infants may have accelerated
these processes so their neuromuscular systems
were physiologically better equipped to execute
actions across a variety of positions.
Third, experimental infants may have primed
their perceptual systems to better process sensory
information. Many perceptual systems are not
mature at birth but develop, in part, as a result of
experience. Each position an infant is held or
placed in allows for different actions and accompanying perceptual experiences. For instance, more
10
Lobo and Galloway
kicking behavior occurs in supine and more handto-mouth behavior occurs in sidelying (Geerdink,
Hopkins, Beek, & Heriza, 1996; Rocha & Tudella,
2008). Changing head position with respect to gravity also provides a variety of visual and vestibular
experiences (Shumway-Cook, 1992). Experience is
important in the development of the visual and
vestibular systems as infants must learn to keep
their heads stable in order to receive reliable perceptual information (Pozzo, Levik, & Berthoz,
1995). Experience is also crucial for infants to learn
how to accurately perceive information from these
systems. For instance, when infants begin to
assume a standing position, this novel upright
experience allows them to adapt their otolithic
responses and sensitivities so they can detect movement of the body in planes not previously experienced through crawling and rolling (Bril & Ledebt,
1998). Therefore, experimental infants likely had
enhanced ability to detect and process perceptual
information across positions.
Changes in Caregivers and Caregiver–Infant Interactions
The interplay between caregivers’ perceptions
and actions and infants’ abilities underlies the developmental process and was a focus of this study.
Even in the first months of life, typical development
involves a cooperative process of communication
and interaction between caregivers and infants as
infants facilitate and regulate their own learning
in conjunction with guidance from more experienced caregivers. Caregivers who are more sensitive
at reading infants’ cues and adapting their interactions to match infants’ abilities and needs have
infants with better social-emotional and cognitive
development at 1–2 years of age (Forcada-Guex,
Pierrehumbert, Borghini, Moessinger, & Muller-Nix,
2006; Treyvaud et al., 2009).
The changes we observed in infants’ abilities
most likely resulted from an interaction between
changes in infants’ abilities and in caregivers’ perceptions and interactions. Interestingly, caregivers
in the two groups reported different effects of participation in the study on their everyday interactions with their infants. Control group caregivers
reported greater social play and improved visual
attention for their infants, while experimental
group caregivers reported greater handling and
positioning play and improved strength and postural control for their infants. These reports suggest
that the changes in infants’ developmental abilities
were not simply the result of 15 min of isolated
experience across 3 weeks in time but that they
were also the result of changes in caregivers’ perceptions and the everyday play interactions
between caregivers and infants that extended well
beyond the prescribed experience period.
Significance of the Findings
The findings of this study have important implications for developmental psychology and early
childhood education. First, they provide comprehensive support for the proposal that caregiver handling and positioning behaviors can instill broad
and long-lasting developmental changes. Second,
they provide additional empirical support for the
proposal that behaviors emerge, evolve, and
become increasing adaptive as a function of a complex history of experiences dependent upon the
interplay of infant abilities, caregiver–infant interactions, and environment. Third, they help us better
understand the complex process of development
and provide the foundation for more specific
hypothesis testing. For instance, many basic questions remain, such as what are the cues caregivers
respond to as they provide more advanced opportunities for their infants in development; what sources
typically inform and guide caregivers’ perceptions
about how to handle, position, and play with their
infants; and how does attainment of novel behaviors
such as reaching, sitting, crawling, or walking affect
daily interactions between caregivers and infants
and the structuring of their environment.
The findings of this study also have important
implications for medical professionals and early
educators working with populations with special
needs. The findings support that caregivers, their
interactions with infants, and the environment they
cocreate with infants are all critical components of
the developmental process and are important components of early assessment and intervention
programs (Wilder & Granlund, 2003). The findings
suggest early interventions should be jointly aimed
at educating caregivers and enabling infants
(Cotnoir-Bichelman, Thompson, McKerchar, &
Haremza, 2006). Therefore, the results support the
notion that a key component of early intervention
should be focused caregiver education targeted
toward advancing foundational abilities at developmentally appropriate times (Mahoney, Robinson, &
Perales, 2004).
Although the results of this study provide
important insights into development, limitations in
the design leave several questions open for future
investigation. First, participants enrolled in the
study by showing motivation to respond to recruit-
Handling and Positioning Advance Development
ment letters and to perform daily play activities
with their infants so our volunteer demographic
may not represent all caregivers in the general population. Although we did not collect data on socioeconomic status from families, the neighborhoods
and occupations we observed suggest none of our
participating families had low socioeconomic status. All of the infants in the study were healthy and
typically developing. Therefore, future research is
necessary to determine how these experiences
apply across contexts and populations, especially as
potential interventions to advance development in
children born with biological or environmental risk
factors (Dodge, 2011). In addition, future research
with larger, more diverse sample groups is necessary to answer important questions, such as for
whom do these experiences have no effect and why
and are there subgroups of caregivers less likely to
perform the experiences. Finally, there remain
important unanswered questions about dosage
effects to better understand the timing and amount
of experience provision that is most effective at
advancing development. In the same vein, we need
to better understand the constraints that may limit
development, such as development of the neuromuscular system, as well as the reasons why the
amount of variability in typical development is so
large. For instance, the typical age range for the
onset of walking is anywhere from 9 to 17 months
of age (Haywood & Getchell, 2009). A better understanding of the sources of this variability and the
constraints that must be overcome for the emergence of novel behaviors is critical for designing
effective early interventions for individuals at risk
for developmental delays and learning disabilities.
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Supporting Information
Additional supporting information may be found
in the online version of this article:
Appendix S1. Social Experience Manual.
Appendix S2. Handling Positioning Manual.
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(other than missing material) should be directed to
the corresponding author for the article.