Step by step: A microgenetic study of the development of ...csivc.csi.cuny.edu/Sarah.Berger/files/publications/BergerChinEtAl2015.pdf · coordinate different components of a plan

British Journal of Developmental Psychology (2015), 33, 106–122

© 2014 The British Psychological Society

www.wileyonlinelibrary.com

Step by step: A microgenetic study of thedevelopment of strategy choice in infancy

Sarah E. Berger1*, Brian Chin2, Sandeep Basra3 and Hannah Kim4

1Department of Psychology, College of Staten Island and The Graduate Center of the

City University of New York, USA2Department of Psychology, Stony Brook University, Stony Brook, New York, USA3Department of Psychology, University of Westminster, London, UK4Department of Psychology, The Graduate Center of the City University of NewYork, USA

To examine patterns of strategy choice and discovery during problem-solving of a novel

locomotor task, 13.5- and 18-month-old infants were placed at the top of a staircase and

encouraged to descend. Spontaneous stair descent strategy choices were documented

step by step and trial by trial to provide a microgenetic account of problem-solving in

action. Younger infants tended to begin each trial walking, were more likely to choose

walking with each successive step, and were more likely to lose their balance and have

to be rescued by an experimenter. Conversely, older infants tended to begin each trial

scooting, were more likely to choose scooting with each successive step, and were

more likely to use a handrail to augment balance on stairs. Documenting problem-

solving microgenetically across age groups revealed striking similarities between

younger infants’ strategy development and older children’s behaviour on more

traditionally cognitive tasks, including using alternative strategies, mapping prior

experiences with strategies to a novel task, and strengthening new strategies. As

cognitive resources are taxed during a challenging task, resources available for weighing

alternatives or inhibiting a well-used strategy are reduced. With increased motor

experience, infants can more easily consider alternative strategies and maintain those

solutions over the course of the trial.

The field of cognitive development has recently shifted its focus from describing

stage-based changes to exploring and understanding the mechanisms underlying

change (Adolph, Robinson, Young, & Gill-Alvarez, 2008; Lemaire, 2010; Siegler, 2007).One of the most fruitful approaches has been the microgenetic analysis of variability in

how school-aged children choose and execute strategies for solving problems. In these

studies, researchers make densely timed observations as children carry out a task,

successfully or not, typically in the context of math- or school-related skills (Bull, Espy,

& Wiebe, 2008; Lemaire & Lecacheur, 2011; Lemaire & Reder, 1999; Siegler, 2007;

Tunteler & Resing, 2002). Siegler’s ‘overlapping waves theory’ lays out the

expectations for the typical development of strategy use in contexts such as

preschoolers using simple tools and grade-schoolers solving arithmetic problems (e.g.,

*Correspondence should be addressed to Sarah E. Berger, Department of Psychology, College of Staten Island, 2800 Victory Blvd.,4S-108, Staten Island, NY 10314, USA (email: [email protected]).

DOI:10.1111/bjdp.12076

106

Chen & Siegler, 2000; Lemaire & Siegler, 1995). On this account, studying within-child

variability, rather than treating it as noise, is a powerful predictor of and tool for

understanding change (Siegler, 2007). Strategy development starts with the acquisition

of new strategies, improves as novices become able to map prior experiences to noveltasks, and culminates with the strengthening of newly acquired strategies (see Chen &

Siegler, 2000, for a review).

The mechanism for change, or what prompts children to move from less to more

efficient and successful strategies, is the automatization that comes from practice. As

cognitive resources that had previously been allocated to the monitoring of strategy

execution become available, they can be reallocated to make problem-solving more

efficient, such as searching for redundancies within existing strategies (Siegler, 2000).

Moreover, as practice increases familiarity with a problem, working memory resourcescan be reallocated to the exploration of alternative strategies (Shrager & Siegler, 1998).

Conversely, a decrease in processing resources in the elderly is associated with impaired

strategy use compared to younger adults, such as less efficient performance or poor

strategy choices (Lemaire, 2010).

One limitation to the typical measurement approaches for studying strategy choice

and problem-solving has been an emphasis on verbal and mathematical problems that,

while yielding rich behavioural data sets for older children, are generally unsuitable for use

with infants (Keen, 2011). As a result, our understanding of the process of strategyacquisition in infancy lacks the level of detail that we have with older children. One

domain in which infants provide as rich behavioural data sets as older children is

locomotor development. Indeed, studies of how infants solve locomotor problems have

revealed that experts in a posture can devise alternative strategies when they encounter

situations where their typical strategies are no longer appropriate. For example, expert

cruisers can bend at thewaist or cruise on their knees to use a low handrail (Berger, Chan,

& Adolph, 2014), and expert walkers choose to crawl so they can navigate squishy

surfaces (Joh & Adolph, 2006), scoot so they can navigate steep slopes (Adolph, 1997),and turn their bodies sideways to grab a handrail so they can navigate narrow bridges

(Berger & Adolph, 2003; Berger, Adolph, & Kavookjian, 2010; Berger, Adolph, & Lobo,

2005).

The overall goal of this studywas to better understand the process of strategy choice in

young infants. As such, our first aimwas to determinewhether infants’ patterns of strategy

discovery and selection followed the same trajectory as those observed in older children

and adults. We designed a locomotor task that could provide a context for observing

development in action, particularly the emergence of problem-solving skills. Specifically,we sought to microgenetically document infants’ spontaneous stair descent strategies.

Previouswork has focusedprimarily on establishing norms forwhen infants learn to climb

stairs (Frankenburg & Dodds, 1967; Gesell, 1934; McGraw & Breeze, 1941) or the social

structures that support infants as they learn to climb stairs (Berger, Theuring, & Adolph,

2007), but we know very little about how infants independently discover new strategies

for climbing stairs (Ulrich, Thelen,&Niles, 1990).Documenting infants’ strategies literally

from step to stepwould yield a high-density sample in real time and capture changewithin

and between trials (Siegler, 1996, 2002). Based on parent reports of how infants firstlearned to descend stairs (Berger et al., 2007), we expected to observe variability in

infants’ spontaneous stair descent when stairs were presented as a novel task that would

provide a differentiated description of children’s strategy choice (Chen & Siegler, 2000;

Siegler, 1996, 2002; Wilmut & Barnett, 2011). For example, in a sample of over 300

families, parents reported that infants typically descended stairs by crawling backwards,

Development of strategy choice 107

walking while holding a banister, or scooting down in a sitting position (Berger et al.,

2007). Moreover, parents reported being actively involved in teaching their infants to

climb stairs, including manoeuvering infants’ limbs into proper position to demonstrate

descent. Allowing infants to solve the novel problem of stair descent independently andwithout constraint would create a relatively naturalistic situation, generate behaviours to

make strategy evolution observable, and circumvent the problem of studying prob-

lem-solving in a pre-verbal population (Siegler, 1996, 1998; Ulrich et al., 1990).

Unlike most motor skills acquired in the first 2 years of life, stair descent carries an

element of risk. Infants are more likely to fall down stairs than any other age group

except elderly adults over the age of 65 (National SAFE KIDS Campaign, 2004; Young,

Torner, Schmitt, & Peek-Asa, 2011). Although infants fall frequently when learning to

cruise while holding onto furniture or walk on flat ground, they do not typically incurserious injury (Adolph et al., 2012; Sugar, Taylor, & Feldman, 1999). In contrast,

approximately 73,000 children between the ages of 6 months and 2 years were

injured on stairs or steps in 2009 (U.S. Consumer Product Safety Commission, 2010).

The extended period of locomotor experience that is required before infants can

coordinate different components of a plan into a strategy or devise alternative

strategies may explain the number of injuries associated with falls on stairs, despite

parents’ best efforts to teach their children safe descent strategies (Berger et al.,

2007). Understanding infants’ strategy choice in the context of stair descent wouldnot only enhance our basic understanding of the development of decision-making in

early childhood, but may offer some practical advice to caregivers about children’s

learning to use stairs.

Our second aim was to investigate the role of expertise in strategy choice as a way to

gain insight into change mechanisms. To do so, we documented 13.5- and 18-month-old

infants’ spontaneous navigation strategies for stair descent when they were placed at

the top of a staircase and encouraged to make their way to a caregiver waiting at the

bottom. This design allowed us to investigate emerging solutions at multiple time scales:Step by step, trial by trial, and between age groups (Adolph, Robinson, et al., 2008;

Badaly & Adolph, 2008; Siegler, 1996). The stair descent task required infants to

generate a goal (reaching a parent at the bottom of a staircase), sequence the steps

necessary to obtain the goal (possibly devising alternative descent strategies for balance

control), and continually monitor their progress towards the goal (to maintain balance).

Each of these task components places a heavy demand on cognitive resources (Carrico,

2013). Moreover, younger infants would have little walking experience and little to no

stair descent experience, so for them, the motor demands of the task would also taxattentional resources (Berger, 2004, 2010; Woollacott & Shumway-Cook, 2002). To

lower their centre of gravity and increase control of balance, infants could theoretically

choose alternative descent strategies such as scooting down on their bottoms facing

forward or backing down stairs. However, despite the increased biomechanical stability

associated with these alternative descent strategies, they are not initially found in

infants’ locomotor repertoires (Adolph, Eppler, & Gibson, 1993). Infants who lack stair

descent experience simply may not perceive these strategies as possibilities for action

until they have amassed sufficient practice navigating stairs with their novice descentskills (e.g., Gibson et al., 1987; Kretch & Adolph, 2013). Examining patterns of infants’

choices and errors on the stair descent task speaks to the role of processing resources in

the development of problem-solving in infancy.

108 Sarah E. Berger et al.

Method

A subset of this data (n = 19) was collected as part of a larger study examining thedevelopment of 13-month-old infants’ ability to inhibit. In the original study, infants

descended a staircase several times before being encouraged to switch to a new staircase.

Primary outcome measures focused on the differences between pre- and post-switch

behaviours. Only data from the pre-switch trials were included in this data set. Data from

the remaining participants (thirteen 13.5-month-olds and seventeen 18-month-olds) were

collected specifically and uniquely for the current study.

Participants

Thirty-two 13.5-month-old infants (16 boys;M = 13 months, 10 days; SD = 13 days) and

seventeen 18-month-old infants (seven boys; M = 18 months, 1 day; SD = 7 days)

participated in this study. The criterion for participation was being able to walk 10 feet

(3.05 m) across the room independently without stopping or falling. We chose

13 months as the age for the younger group because at that age, most infants have

minimal to no stair descent experience and because pilot testing confirmed that stair

descent was a challenging motor task that elicited rich motor behaviours for that agegroup (Berger, 2010; Berger et al., 2007). We chose 18 months as the age for the older

group because in a previous survey of over 700 families about their infants’ navigation of

stairs, most infants had learned to descend stairs between 17 and 20 months (Berger

et al., 2007). Families were recruited via a purchased commercial mailing list. All infants

were healthy and born at term. The sample was approximately 1/3 White, 1/3 Hispanic,

and 1/3 other, including parents who refused to report; was primarily of middle-class

socio-economic status; and lived in the New York City metropolitan area. An

experimenter interviewed parents about infants’ crawling, walking, stair-climbing, andhandrail experience (see Table 1). Interviewers used a strict protocol of probe questions

regarding dates of events (Berger et al., 2007). Parents used ‘baby books’ or calendars to

augment theirmemories formilestone dates. Families received a small thank-you gift and a

diploma for participating.

Staircase apparatus

The experimental apparatus (see Figure 1) was a 54-cm-high wooden staircase with fivesteps down to the floor (step height = 14.29 cm) and custom-built low handrails

(21.27 cm from the step) on both sides that came to approximately hip height on an

average toddler. The top step (42 cm2)waswider than the other four (19 cmdeep) so that

participantswouldhave room tomanoeuver if theywanted to change or explore positions

before descending. Four poles at the corners (34.29 cm high) of the top step were

available to provide support for balance while standing or shifting body postures before

stair descent. All steps and risers of the staircase were carpeted.

Procedure

All participants completed five trials. At the start of each trial, an experimenter placed

infants close to the centre of the platform, 15–20 cm from the edge. On each trial, infants

descended the stairs to a caregiverwhowaited at the bottom. Parents called to their babies

from the foot of the stairs and offered words of encouragement, but did not provide


Table

1.Infants’locomotorandstairexperience

13-M

onth-olds

18-M

onth-olds

Mean

(SD)

Range

NMean

(SD)

Range

N

Walkingexperience

2months,5days

(27days)

7days–3months,16days

32

5months,3days(2

month,

2days)

2months,13days–9months,

29days

17

Ascentexperience

2months,26days

(1month,22days)


25

4months,17day

(2months,

14days)

1day–9

months,23days

15

Descentexperience

1month,28days

(1month,10days)


11

4month,26days(3

months,

15days)

1month,1

day–9

months,

5days

5

Numberofinfantswith

Stairs

inthehome

913

Priorhandrailexperience

712


instruction on how to descend. A highly trained experimenter spotted the infants by

following alongside them to ensure their safety, but did not otherwise help the infants

with descent. The experimenter held their hands near the infants to spot them, but did not

touch them unless they started to fall. The session was videotaped with a single camerathat captured each trial with a point of viewof slightly above and facing the participants as

they descended the stairs. Sessions lasted 30 min.

Results

Data codingData from each test session were coded from videotape using OpenSHAPA, a

computerized video coding system (now Datavyu, datavyu.org; Sanderson et al., 1994).

Toddlers contributed five trials each, yielding 245 total trials for coding (160 from 13.5-

month-olds and 85 from 18-month-olds). A primary coder coded all outcome measures

from video. To ensure inter-rater reliability, a second coder independently coded 25% of

all outcome measures. Inter-rater agreement ranged from 0.98 to 1.0, and p-values for all

Cohen’s kappa coefficients <.01.

Variability in descent strategies

Coders documented all strategies infants spontaneously used to descend the staircase.

Infants descended the stairs in three ways: Walking if they walked down the stairs,

scooting if they bumped down the stairs on their bottoms, and backing if they moved

backwards on hands and knees down the stairs. Infants could perform more than one

descent strategy on each trial. A 5 (trial) 9 5 (step of the staircase [top step to bottom

step]) 9 2 (age group) repeated-measures ANOVA, with trial and step number aswithin-subjects factors and age group as a between-subjects factor, revealed no effect of

trial on the frequency that infants walked down the stairs, but did show main effects for

step of the staircase and for age, F(1, 47) = 4.62, p < .04 and F(1, 47) = 6.47, p < .02,

respectively, and a significant quadratic effect of step, F(1, 47) = 8.81, p < .01, with

(a) (b) (c)

Figure 1. Staircase apparatus with stairs connected to starting platform. Parents waited at the bottom.

An experimenter followed alongside infants to ensure their safety, but did not otherwise assist. Infants

spontaneously chose their own descent strategies (a) scooting, (b) walking, or (c) backing, on each of five

descent trials.


13.5-month-olds more likely to walk with each step and 18-month-olds less likely to walk

with each step over the course of each trial (see Figure 2, filled markers). For walk

frequency, post-hoc analyses of step of the staircase revealed that the effect was primarily

driven by an increase in walking on the later steps for the younger infants.

A 5 (trial) 9 5 (step of the staircase) 9 2 (age group) repeated-measures ANOVA onthe frequency that infants scooted down the stairs revealed no effect of trial, but did show

main effects for step and for age, F(1, 47) = 8.88, p < .01 and F(1, 47) = 10.35, p < .01,

respectively, and a significant quadratic effect of step, F(1, 47) = 6.94, p = .01, with

13.5-month-olds less likely to scoot with each step and 18-month-oldsmore likely to scoot

with each step over the course of each trial (see Figure 2, open markers). For scoot

frequency, post-hoc analyses of step of the staircase revealed that the effect was primarily

driven by a decrease in scooting from step to step as each trial progressed.

A 5 (trial) 9 5 (step of the staircase) 9 2 (age group) repeated-measures ANOVArevealed nomain effects of trial, step, or group on the frequency that infants backed down

the stairs because infants almost never did so (n = 9 trials). Thus, on most trials, infants

performed 1 or 2 strategies, although one infant did perform all three strategies on a single

trial.

Role of experience on stairs

Because the way in which infants executed a descent strategy is likely due to theirproficiency navigating stairs, as well as their planning skills (van der Meer, 1997), we

examined whether infants’ experience on stairs prior to visiting the laboratory was

relevant. Calculating infants’ stair experience was not as straightforward as doing so for

other motor milestones. Typically, experience is operationalized as the number of days

since an infant first performed a skill to criterion. However, in interviewing parents about

their children’s experiences with stairs, parents often reported that infants may have

demonstrated their ability to ascend or descend a staircase, soon after which the parents

restricted access to only that one time. Thus, unlike days since the onset of walking orcrawling, days since the first ascending or descending may not reflect an accrual of

practice (Berger et al., 2007). In an attempt to more accurately capture infants’ actual

descent experiences on stairs, we categorized infants as having no experiencewith stairs

(no stairs at home, never gone down stairs; n = 21), some experiencewith stairs (stairs at

Figure 2. Effects of step, trial, and infants’ age on descent strategy choices: Walking (filled circles),

scooting (open circles), or backing (no markers).


home, but never gone down, n = 12; or no stairs at home, but has gone down, n = 5), or

full experience with stairs (stairs at home, has gone down stairs; n = 11).

Using handrails

Light touches of a handrail can augment balance and provide postural support (Barela,

Jeka, & Clark, 1999; Chen, Metcalfe, Chang, Jeka, & Clark, 2008; Metcalfe & Clark, 2000),

and experiencedwalkers can use handrails as a tool for balance control during locomotion

(Berger & Adolph, 2003; Berger et al., 2005). We coded whether infants touched the

handrail during stair descent. A 5 (trial) 9 2 (age group) 9 4 (experience on stairs)

repeated-measures ANOVA on the proportion of trials that infants used the handrail

revealed a significant main effect for age, with 18-month-olds using the handrail on 92% oftrials and 13.5-month-olds using the handrail on only 57% of trials, F(1, 42) = 9.57,

p < .01.

Using the experimenter

Coders documented the ways that the experimenter interacted with the infants as they

descended the stairs.We counted rescueswhether the experimenter had to touch infants

to prevent them from falling as they descended. A 5 (trial) 9 5 (step) 9 2 (agegroup) 9 4 (experience on stairs) repeated-measures ANOVA on the proportion of trials

that the experimenter rescued the infants revealed main effects for step, F(1, 42) = 6.54,

p < .02, age group, F(1, 42) = 33.30, p < .01, and a step by age group interaction, F(1,

42) = 5.66, p < .03. 13.5-month-olds had to be rescued significantly more often than

18-month-olds, particularly at the end of each trial (see Figure 3, open and filled triangle

markers).

We also coded whether infants used the experimenter to augment balance if they

touched or grabbed the experimenter after they had left the starting platform. A 5(trial) 9 5 (step) 9 2 (age group) 9 4 (experience on stairs) repeated-measures ANOVA

on the proportion of trials that infants used the experimenter for support revealed a main

effect only for experience on stairs, F(3, 42) = 3.06, p < .04 (see Figure 4a). Post-hoc

analyses revealed that infants with the least experience (no stair descent experience, no

Figure 3. Effects of step, trial, and infants’ age on the role of the experimenter: Used by infants to

augment balance (circle markers), having to rescue infants when they started to fall (triangle markers), or

not involved beyond spotting the infants (square markers).


stairs at home) and infants with the most experience (stairs at home, stair descent

experience) used the experimenter significantly less often than infants with only

moderate amounts of experience (all p’s < .05).

Finally, if neither the experimenter touched the infant nor the infant reached out to the

experimenter for assistance, we coded that the experimenter remained uninvolved in

infants’ balance as they descended, beyond simply spotting them for safety. A 5 (trial) 9 5(step) 9 2 (age group) 9 4 (experience on stairs) repeated-measures ANOVA on the

proportion of trials that no touching occurred between the experimenter and the infant

revealed a main effect for age group, F(1, 42) = 48.64, p < .01. Eighteen-month-olds

ignored the experimenter significantly more often than the 13.5-month-olds did (see

Figure 3, open and filled square markers).

LatencyLatencywas defined as the time from the start of the trial (infantswere placed in the centre

of the starting platform, were on task directed to the goal, and were not held by an

experimenter) until they took their first step off the platform and reflects the time it took

infants to decide how to descend the first step of the staircase. Due to video equipment

failure, latency is missing for two trials for one 13.5-month-old, who is dropped from the

repeated-measures analysis.

A 2 (age group) 9 4 (experience on stairs) ANOVAof infants’mean latency to descend

revealed a main effect for age and a significant interaction between experience and age,F(1, 42) = 5.90, p = .02 and F(2, 42) = 3.04, p = .05, respectively. As shown in Figure 4b,

13.5-month-olds tended to have longer latencies than 18-month-olds, but the difference

between the groups is exaggerated for the most experienced infants, where 13.5-month--

olds takemore time to leave the starting platform than all other groups and 18-month-olds

take less time than all other groups.

Discussion

This study examined the development of problem-solving strategies by microcoding how

13.5- and 18-month-old walking infants coped with stair descent in the laboratory. In the

(a) (b)

Figure 4. Effects of age, access to stairs at home, and stair descent experience on (a) infants’ use of the

experimenter to augment balance and (b) trial latency. Error bars represent standard error. There were

no 18-month-olds in the No Stairs/Descent group.


tradition of using action to draw inferences about infants’ ‘hidden’ cognition (e.g., Keen,

2011; Oakes & Plumert, 2002; Piaget, 1954), our goal was to make the process of

problem-solving observable. We documented the strategies that infants used to descend

stairs and whether they modified their strategies from step to step as they descended ashort staircase and from trial to trial over the course of the session. Infants’ descent

behaviours in the laboratory were related to age and individual differences in stair

experience outside of the laboratory. Of the three observed descent strategies, infants

used walking and scooting most frequently; backing down stairs was rare.

Taking a microgenetic approach to understanding how infants solved the problem of

stair descent revealed variability in infants’ descent strategies. Both age groups used

multiple strategies within a single trial, usually switching between scooting and walking

from step to step, but the pattern of strategy switching varied with age. As a group, most13.5-month-olds (56–69%) tended to start each trialwalking down the first step. However,

over the course of the trial, the proportion of the sample choosing towalk down each step

increased significantly (to 70–80% by the last step) and this pattern repeated anew for

eachof the five trials, as if beingplaced at the topof the platformwas the start of an entirely

new problem. The lack of learning from trial to trial played out as higher rates of walking

and lower rates of scooting for the younger group at the end of a trial followedby renewed

lower rates of walking and higher rates of scooting and ultimately a return to a greater

likelihood of walking/lower likelihood of scooting by the end of the next trial. Given theproportionally greater height of the risers for the group, walking down stairs was a

particularly bad choice for the 13.5-month-olds; they had to be rescued from falling down

the stairs when they tried to walk. As a group, the 18-month-olds started each trial

roughly split between whether they scooted or walked down the first step. Like the

13.5-month-olds, they renewed this pattern at the start of each trial. Unlike the

13.5-month-olds, however, they were more likely to scoot the rest of the way down

the staircase.

Scooting lowers the centre of mass, in turn reducing the risk of toppling, but doesrequire greater motor coordination and leg strength. It may be that only older infants had

the strength and coordination to execute the scooting strategy or that the younger infants

did not have the attentional resources to add an additional step to theirmotor plan or some

combination of the two. Although parents report preferring their infants to back down

stairs for safety reasons (Berger et al., 2007), and despite backing being an optimal

biomechanical strategy for descent, itwas an infrequentway for infants in both age groups

to descend. Backing requires that infants inhibit being visually and motorically ‘captured’

by the goal so that they can turn away from it (Diamond, 1991; Lockman & Adams, 2001),counterintuitively move backward, and keep the goal in mind. However, children are

heavily dependent on visual feedback for stair descent until age 4 or later (Cowie,

Atkinson, & Braddick, 2010). Infants’ reliance on visual information during stair descent

may have prohibited them from choosing backing as a descent strategy; anecdotally, the

few infantswho did back down the stairs turned their head to keep the goal in sight as they

did so. Scootingmaybe a satisfactory compromise between the stability of backing and the

visual information gained while walking, but was only a frequent descent strategy for the

18-month-olds. Newly walking infants may be so dependent on visual information duringstair descent that they are more likely to choose a less stable stair descent strategy if it

allows them to keep the stairs and the goal in view.

As new skills are acquired and mastered, variability in strategy use is typical (Adolph,

Robinson, et al., 2008; Lemaire & Siegler, 1995). Understanding the pattern and

trajectory of that variability helps us understand the process underlying acquisition of


problem-solving skills. In this study, scooting down stairs and using the handrail were

alternative descent strategies that provided increased stability for toddlers. However, new

walkers can be reluctant to switch to alternative locomotor strategies, even when

continuing towalkmeans bumping a head on a low entrance or trying to squeeze throughan impossibly narrow space (Berger, 2010; Berger & Scher, 2012; Brownell, Zerwas, &

Ramani, 2007; Comalli & Adolph, 2013). In this case, for the few 13.5-month-olds who

came up with the strategy of scooting at the start of the trial, maintaining that posture for

the duration of the trial was difficult. In addition, the younger infants did not incorporate

an external object into their action plan, with only around half of the group using the

handrail, and almost none reaching out to the experimenter for help. The overlapping

waves model of adaptive strategy choice would predict that with increased experience,

the use of alternative strategies should increase (Lemaire & Siegler, 1995; Siegler, 2005).Indeed, the 18-month-olds, who on average had more walking and descent experience

than the 13.5-month-olds, maintained the alternative descent strategy of scooting for a

greater proportion of each trial and almost all used the handrail for support (they did not

use the experimenter for help, either, but that was because they used the handrail

instead). Moreover, infants with moderate amounts of experience reached out to the

experimenter during descent more often than infants with no descent experience at all

prior to participating in the study. Augmenting balance with an adult may serve as an

alternative descent strategy available to infants with minimal experience on stairs that isless sophisticated than handrail use, but possibly reflecting prior experience in which an

adult taught infants to descend.

A possible explanation for the observed pattern of strategy shifts could be the

tendency of younger children to demonstrate ‘utilization deficiencies’ (Clerc & Miller,

2013; Gaultney, Kipp, & Kirk, 2005; Schneider, Kron, Hunnerkopf, & Krajewski, 2004).

Utilization deficiencies were first identified by Miller (1990) as part of the normal

progression of strategy development in which a strategy is used properly and

spontaneously, but to no benefit. In keeping with the tradition of studying utilizationdeficiencies microgenetically (Coyle & Bjorklund, 1996; Schwenck, Bjorklund, &

Schneider, 2007), we documented 13-month-olds’ tendency to switch to walking at later

steps on a trial and the increased likelihood that they required rescue on those later steps.

This patternwas parallel to the utilization deficiencies seen in tasks that traditionally study

memory, selective attention, organization, and reading comprehension (Bjorklund, Coyle,

& Gaultney, 1992; Gaultney, 1995; Gaultney et al., 2005; Miller, 1994). Consistent with

Miller’s account of strategy development, 18-month-olds did not show evidence of

utilization deficiencies – upon switching to a scooting strategy, they experienced thebenefits that the younger infants did not – most likely due to their increased locomotor

experience and greater pool of attentional resources.

Taken together, infants’ sequence of behaviours suggests that their exploration largely

focused on how to approach the 1st step of the staircase, rather than on the creation of a

detailed plan for navigating the staircase from top to bottom. For example, 13-month-olds

typically started out with a good descent strategy, but soon switched to a bad one, with

rescues happening primarily later in the trial. It is unlikely that this would be part of a

general navigation plan given how effortful and taxing it is for new walkers to switchbetween postures (Berger, 2010) and how aversive they find being rescued from a fall

(e.g., Adolph, 2000; Berger et al., 2005; Franchak & Adolph, 2012). Moreover, the

18-month-olds were essentially at chance in their choice of strategy on the first step, but

consistently switched to a more efficient strategy for subsequent steps. If they were

planning ahead from the platform, we might expect consistency in strategy choice from


the initial step, rather than settling on it eventually. Thus, it appears as though infants’

planning happened online as they faced the challenge of each new step, rather than at the

start of a sequence of planned movements.

Individual differences in experience descending stairs also shed light onto thedevelopment of problem-solving. One of the hallmarks of expertise is understandingwhat

information is relevant to the task at hand and how to use that information effectively

(Adolph, Karasik, & Tamis-LeMonda, 2010; Tamis-LeMonda et al., 2008). Infants in both

age groups who had the most experience descending stairs – having stairs at home and

having descended stairs prior to visiting the laboratory – approached the problem of

descent differently than infants withminimal descent experience. However, as with their

choice of descent strategies, approach differed by age. Experienced 18-month-olds

recognized the problem and quickly came up with a solution – they left the startingplatform in a fraction of the time of all other groups. In contrast, experienced

13-month-olds took significantly longer to plan their descent strategy compared to all

other groups. Their expertise gave them thewherewithal to recognize that they needed to

plan their solution, but they were slower and more deliberate than the older infants in

carrying out the plan. Both experienced groups’ exploratory behaviour suggested that

they recognized stair descent as a novel problem and that their solution to this problem

drew on their unique and specific experiences (van der Meer, 1997; Ulrich et al., 1990).

Adaptive locomotion involves both motor proficiency and higher level cognitiveabilities (Berger & Adolph, 2003). Our microgenetic coding of strategy use, exploratory

behaviour, and success on the task reflected elements of planning and decision-making

associated with problem-solving. However, our measure of experience was admittedly a

crude way to capture proficiency. For stair descent in particular, with only parent reports

of the first day that infants performed the skill to criteria to go on, experience may be

harder tomeasure than othermotormilestones because of the inextricable role of parents

creating constraints and opportunities for practice. The finding that our rudimentary

measure of experience predicted one strategy suggests that it may be fruitful for futurework to delve further into the role of proficiency with either biomechanical measure-

ments or prospective documentation of stair experience. Previous work has shown that

measures of locomotor proficiency predict individual differences when the locomotor

task pushes infants to the limits of their abilities (Berger & Adolph, 2003). Our measure of

experience may not have been sensitive enough to tease apart the contributions of skill

and cognitive ability for all strategy choices, but a more precise measure may reveal a

greater role of experience.

The development of strategy use has typically focused on older children learning tosolve cognitive or reasoning tasks and has taken advantage of participants’ verbal abilities

to respond toquestions or provide commentary on their actions (e.g., Chen&Klahr, 1999;

although Adolph, 1997; andMcCarty, Clifton, &Collard, 1999; are some exceptions). One

drawback has been the unsuitability of thesemethods for usewith pre-verbal populations.

In contrast, our approach to studying locomotor problem-solving has the advantage of

documenting strategy use and decision-making in a younger population that is otherwise

unable to comment on their own actions. We see striking parallels between infants’

behaviour in this locomotor problem-solving task and older children’s behaviour onmore‘cognitive’ tasks. For example,we got a glimpse of the first phase of strategy development,

the acquisition of new strategies, with the appearance of new locomotor descent

strategies in the repertoire of younger infants, and saw the utilization of new strategies in

full force by the older infants. The second phase of strategy development ismapping prior

experiences with strategies to the novel task. In this case, we observed the infants with


prior stair experience treating the laboratory task differently from theway infants with no

or minimal experience treated the task. Finally, we observed phase three of strategy

development, strengthening the newly acquired strategy. Over the course of several

months spent acquiring relevant walking and stair descent experience, the older infantsreified the more effective solutions to the problem of stair descent. Within each trial, we

observed a mix of an initial failing to rely on newly acquired strategies, but then the

strengthening of the usage of those strategies for the 18-month-olds.

These findings may be useful for parents whose children are learning to climb stairs.

Previous work has shown that although infants’ may have locomotor expertise across a

variety of terrains in one posture, they need to attain that expertise all over again upon the

acquisition of a new posture (e.g., Adolph, 1997, 2000; Berger, 2010). Likewise, in this

study, experienced walkers solved the novel problem of stair descent more effectivelythan novice walkers. Parents’ attempts to teach new, motorically safe, but cognitively

challenging descent strategies to new walkers as they learn to descend stairs would be

ineffective before infants have attained sufficient motor and cognitive proficiency.

Parents’ vigilance upon the onset of infants’ acquisition of stair descent is crucial,

particularly for new walkers.

Previous work has documented variability in locomotor strategies from trial to trial as

new skills were acquired or revealed the repertoire of strategies available to experts

(Adolph, 1997; Berger et al., 2005). Documenting descent strategy on a step-by-step basisin this study has helped to provide a new level of precision in understanding the process of

acquiring the expertise required for successful strategy choice. As cognitive resources are

taxed during a challenging task, performing the task itself may reduce the resources

available for weighing alternatives or inhibiting an often-used strategy. On each trial,

younger infants entertained an alternative,more stable strategy for descent (scooting), but

often reverted to their typical locomotor strategy of walking before the end of the trial.

During each new trial, they considered again the possibility of using a better, safer

strategy, but themotor difficulty of stair descent combinedwith the cognitive demands ofentertaining alternative plans of action may have overtaxed their resources. In contrast,

the older infants who did not have to attend so closely to the motor demands of descent

could more easily consider alternative strategies, including switching to scooting and

using a handrail, and maintain those solutions over the course of a trial.

In sum, documenting within- and between-trial problem-solving at both microgenetic

and cross-sectional levels in a locomotor task yielded a rich behavioural data set and

helped to chart the process of becoming increasingly proficient and efficient in strategy

choice and use. Studying learning in action demonstrated that stair descent requiresproblem-solving strategies similar to those previously observed in other forms of adaptive

locomotion, as well as in tasks more broadly construed as cognitive (Berger, 2010; Berger

& Adolph, 2007; Carrico, 2013).

Acknowledgements

Wegratefully acknowledgeDr. LanaKarasik and themembers of the ChildDevelopment Lab at

the College of Staten Island for their constructive feedback on earlier drafts of this manuscript.

A portion of this research was supported by PSC-CUNY Research Grant 40-175 to Sarah E.

Berger, Department of Psychology, the College of Staten Island, and theGraduate Center of the

City University of New York. A portion of this data was presented at the Seventeenth

International Conference on Infant Studies, Baltimore, MD, 2010.We thankMohamedHussein

for his help with data coding and the line drawings.


References

Adolph, K. E. (1997). Learning in the development of infant locomotion.Monographs of the Society

for Research in Child Development, 62(3), 1–158.Adolph, K. E. (2000). Specificity of learning: Why infants fall over a veritable cliff. Psychological

Science, 11, 290–295. doi:10.1111/1467-9280.00258Adolph, K. E., Cole,W. G., Komati, M., Garciaguirre, J. S., Badaly, D., Lingeman, J. M., . . . Sotsky, R. B.

(2012). Howdo you learn towalk? Thousands of steps and dozens of falls per day. Psychological

Science, 23, 1387–1394. doi:10.1177/0956797612446346Adolph, K. E., Eppler, M. A., & Gibson, E. J. (1993). Crawling versus walking infants’ perception of

affordances for locomotion over sloping. Child Development, 64, 1158–1174. doi:10.1111/j.1467-8624.1993.tb04193.x

Adolph,K. E., Karasik, L. B., &Tamis-LeMonda, C. S. (2010). Using social information to guide action:

Infants’ locomotion over slippery slopes. Neural Networks, 23, 1033–1042. doi:10.1016/j.neunet.2010.08.012

Adolph, K. E., Robinson, S. R., Young, J. W., & Gill-Alvarez, F. (2008). What is the shape of

developmental change? Psychological Review, 115, 527–543. doi:10.1037/0033-295X.115.3.527

Badaly, D., & Adolph, K. E. (2008). Beyond the average: Walking infants take steps longer than their

leg length. Infant Behavior andDevelopment, 31, 554–558. doi:10.1016/j.infbeh.2007.12.010Barela, J., Jeka, J. J., & Clark, J. (1999). The developmental use of somatosensory information during

the acquisition of independent upright stance. Infant Behavior andDevelopment, 22, 89–104.doi:10.1016/S0163-6383(99)80007-1

Berger, S. E. (2004). Demands on finite cognitive capacity cause infants’ perseverative errors.

Infancy, 5, 217–238. doi:10.1207/s15327078in0502_7Berger, S. E. (2010). Locomotor expertise predicts infants’ perseveration errors. Developmental

Psychology, 46, 326–336. doi:10.1037/a0018285Berger, S. E., & Adolph, K. E. (2003). Infants use handrails as tools in a locomotor task.

Developmental Psychology, 39, 594–605. doi:10.1037/0012-1649.39.3.594Berger, S. E., & Adolph, K. E. (2007). Learning and development in infant locomotion. In C. von

Hofsten & K. Rosander (Eds.), From action to cognition (pp. 237–255). Amsterdam, the

Netherlands: Elsevier.

Berger, S. E., Adolph, K. E., & Kavookjian, A. E. (2010). Bridging the gap: Solving spatial means–endsrelations in a locomotor task. Child Development, 81, 1367–1375. doi:10.1111/j.1467-8624.2010.01478.x

Berger, S. E., Adolph, K. E., & Lobo, S. A. (2005). Out of the toolbox: Toddlers differentiate wobbly

and wooden handrails. Child Development, 76, 1294–1307. doi:10.1111/j.1467-8624.2005.00851.x

Berger, S. E., Chan, G., & Adolph, K. E. (2014). What cruising infants understand about support for

locomotion. Infancy, 19, 117–137. doi:10.1111/infa.12042Berger, S. E., & Scher, A. (2012). What is the role of sleep in toddlers’ motor learning? Poster

presented at the Eighteenth Biennial International Conference on Infant Studies, Minneapolis,

MN.

Berger, S. E., Theuring, C.,&Adolph,K. E. (2007).Howandwhen infants learn to climb stairs. Infant

Behavior and Development, 30, 36–49. doi:10.1016/j.infbeh.2006.11.002Bjorklund, D. F., Coyle, T. R., & Gaultney, J. F. (1992). Developmental differences in the acquisition

and maintenance of an organizational strategy: Evidence for the utilization deficiency

hypothesis. Journal of Experimental Child Psychology, 54, 434–448. doi:10.1016/0022-0965(92)90029-6

Brownell, C. A., Zerwas, S., & Ramani, G. B. (2007). “So big”: The development of body

self-awareness in toddlers. Child Development, 78, 1426–1440. doi:10.1111/j.1467-8624.2007.01075.x


Bull, R., Espy, K. A., & Wiebe, S. A. (2008). Short-term memory, working memory, and executive

functioning in preschoolers: Longitudinal predictors of mathematical achievement at age

7 years. Developmental Neuropsychology, 33, 205–228. doi:10.1080/87565640801982312Carrico, R. L. (2013). Attention andmultistep problem solving in 24-month-old children. Journal of

Cognition and Development, 14, 529–545. doi:10.1080/15248372.2012.689388Chen, Z., & Klahr, D. (1999). All other things being equal: Acquisition and transfer of the control of

variables strategy. Child Development, 70, 1098–1120. doi:10.1111/1467-8624.00081Chen, L. C., Metcalfe, J. S., Chang, T. Y., Jeka, J. J., & Clark, J. E. (2008). The development of infant

upright posture: Sway less or sway differently? Experimental Brain Research, 186, 293–303.doi:10.1007/s00221-007-1236-1

Chen, Z., & Siegler, R. S. (2000). Across the great divide: Bridging the gap between understanding of

toddlers’ and older children’s thinking. Monographs of the Society for Research in Child

Development, 65(1), 1–96.Clerc, J., & Miller, P. H. (2013). Utilization deficiencies and transfer of strategies in preschoolers.

Cognitive Development, 28, 76–93. doi:10.1016/j.cogdev.2012.09.003Comalli, D. M., & Adolph, K. E. (2013). Stop, drop, and crawl: Infants select locomotor strategies

based on overhead clearance. Poster presented at Society for Research in Child Development,

Seattle, WA.

Cowie, D., Atkinson, J., & Braddick, O. (2010). Development of visual control in stepping down.

Journal of Experimental Brain Research, 202, 181–188. doi:10.1007/s00221-009-2125-6Coyle, T. R., & Bjorklund, D. F. (1996). The development of strategic memory: A modified

microgenetic assessment of utilization deficiencies. Cognitive Development, 11, 295–314.doi:10.1016/S0885-2014(96)90006-4

Diamond, A. (1991). Neuropsychological insights in themeaning of object concept development. In

S. Carey & R. Gelman (Eds.), The epigenesis of mind (pp. 67–110). Hillsdale, NJ: Erlbaum.

Franchak, J.M.,&Adolph,K. E. (2012).What infants knowandwhat theydo: Perceiving possibilities

for walking through openings. Developmental Psychology, 48, 1254–1261. doi:10.1037/

a0027530

Frankenburg, W. K., & Dodds, J. B. (1967). The Denver developmental screening test. Journal of

Pediatrics, 71, 181–191. doi:10.1016/S0022-3476(67)80070-2Gaultney, J. F. (1995). The effect of prior knowledge and metacognition on the acquisition of a

reading comprehension strategy. Journal of Experimental Child Psychology, 59, 142–163.doi:10.1006/jecp.1995.1006

Gaultney, J. F., Kipp, K., & Kirk, G. (2005). Utilization deficiency and working memory capacity in

adult memory performance: Not just for children anymore. Cognitive Development, 20, 205–213. doi:10.1016/j.cogdev.2005.02.001

Gesell, A. (1934). Infant behavior: Its genesis and growth. New York, NY: Greenwood Press.

Gibson, E. J., Riccio, G., Schmuckler, M. A., Stoffregen, T. A., Rosenberg, D., & Taormina, J. (1987).

Detection of the traversability of surfaces by crawling and walking infants. Journal of

Experimental Psychology: Human Perception and Performance, 13, 533–544. doi:10.1037/0096-1523.13.4.533

Joh, A. S., & Adolph, K. E. (2006). Learning from falling. Child Development, 77, 89–102. doi:10.1111/j.1467-8624.2006.00858.x

Keen, R. (2011). The development of problem solving in young children: A critical cognitive skill.

Annual Review of Psychology, 62, 1–21. doi:10.1146/annurev.psych.031809.130730Kretch, K. S., & Adolph, K. E. (2013). Cliff or step? Posture-specific learning at the edge of a drop-off.

Child Development, 84, 226–240. doi:10.1111/j.1467-8624.2012.01842.xLemaire, P. (2010). Cognitive strategy variations during aging. Current Directions in Psychological

Science, 19, 363–369. doi:10.1177/0963721410390354Lemaire, P., & Lecacheur, M. (2011). Age-related changes in children’s executive functions and

strategy selection: A study in computational estimation. Cognitive Development, 26, 282–294.doi:10.1016/j.cogdev.2011.01.002


Lemaire, P., & Reder, L. (1999). What affects strategy selection in arithmetic? The example of parity

and five effects on product verification. Memory & Cognition, 27, 364–382. doi:10.3758/BF03211420

Lemaire, P., & Siegler, R. S. (1995). Four aspects of strategic change: Contributions to children’s

learning of multiplication. Journal of Experimental Psychology: General, 124, 83–97. doi:10.1037/0096-3445.124.1.83

Lockman, J. J., & Adams, C. D. (2001). Going around transparent and grid-like barriers: Detour ability

as a perception-action skill.Developmental Science, 4, 463–471. doi:10.1111/1467-7687.00188McCarty, M. E., Clifton, R. K., & Collard, R. R. (1999). Problem solving in infancy: The emergence of

an action plan. Developmental Psychology, 35, 1091–1101. doi:10.1037/0012-1649.35.4.1091McGraw, M. B., & Breeze, K. W. (1941). Quantitative studies in the development of erect

locomotion. Child Development, 12, 267–303.Metcalfe, J. S., & Clark, J. E. (2000). Sensory information affords exploration of posture in newly

walking infants and toddlers. Infant Behavior & Development, 23, 391–405. doi:10.1016/S0163-6383(01)00054-6

Miller, P. H. (1990). The development of strategies of selective attention. In D. F. Bjorklund (Ed.),

Children’s strategies: Contemporary views of cognitive development (pp. 157–184). Hillsdale,NJ: Erlbaum.

Miller, P. H. (1994). Individual differences in children’s strategy behaviors: Utilization deficiencies.

Learning and Individual Differences, 6, 285–307. doi:10.1016/1041-6080(94)90019-1National SAFE KIDS Campaign (2004). Falls fact sheet. Retrieved from http://www.preventinjury.

org/PDFs/FALLS.pdf

Oakes, L. M., & Plumert, J. M. (2002). Variability in thirteen-month-old infants’ touching patterns in

the sequential-touching task. Infant Behavior and Development, 25, 529–549. doi:10.1016/S0163-6383(02)00149-2

Piaget, J. (1954). The construction of reality in the child. New York, NY: Free Press.

Sanderson, P. M., Scott, J. J. P., Johnston, T., Mainzer, J., Watanabe, L. M., & James, J. M. (1994).

MacSHAPA and the enterprise of Exploratory Sequential Data Analysis (ESDA). International

Journal of Human-Computer Studies, 41, 633–681.Schneider, W., Kron, V., Hunnerkopf, M., & Krajewski, K. (2004). The development of young

children’s memory strategies: First findings from the Wurzburg Longitudinal Memory Study.

Journal of Experimental Child Psychology, 88, 193–209. doi:10.1016/j.jecp.2004.02.004Schwenck, C., Bjorklund, D. F., & Schneider, W. (2007). Factors influencing the incidence of

utilization deficiencies and other patterns of recall/strategy-use relations in a strategic memory

task. Child Development, 78, 1771–1787. doi:10.1111/j.1467-8624.2007.01090.xShrager, J., & Siegler, R. S. (1998). SCADS: A model of children’s strategy choices and strategy

discoveries. Psychological Science, 9, 405–410. doi:10.1111/1467-9280.00076Siegler, R. S. (1996).Emergingminds: The process of change in children’s thinking. NewYork, NY:

Oxford University Press.

Siegler, R. S. (1998). Children’s thinking (3rd ed.). Upper Saddle River, NJ: Prentice Hall.

Siegler, R. S. (2000). The rebirth of children’s learning. Child Development, 71 (1), 26–35. doi:10.1111/1467-8624.00115

Siegler, R. S. (2002). Microgenetic studies of self-explanation. In N. Granott & J. Parziale (Eds.),

Microdevelopment: Transition processes in development and learning (pp. 31–58). NewYork, NY: Cambridge University Press.

Siegler, R. S. (2005). Children’s learning. American Psychologist, 60, 769–778. doi:10.1037/0003-066X.60.8.769

Siegler, R. S. (2007). Cognitive variability. Developmental Science, 10, 104–109. doi:10.1111/j.1467-7687.2007.00571.x

Sugar, N. F., Taylor, J. A., & Feldman, K.W. (1999). Bruises in infants and toddlers: Those who don’t

cruise rarely bruise. Archives of Pediatrics and Adolescent Medicine, 153, 399–403. doi:10.1001/archpedi.153.4.399


Tamis-LeMonda, C. S., Adolph, K. E., Lobo, S. A., Karasik, L. B., Ishak, S., & Dimitropoulou, K. A.

(2008). When infants take mothers’ advice: 18-month-olds integrate perceptual and social

information to guide motor action. Developmental Psychology, 44, 734–746. doi:10.1037/0012-1649.44.3.734

Tunteler, E., &Resing,W.C.M. (2002). Spontaneous analogic transfer in 4-year-olds: Amicrogenetic

study. Journal of Experimental Child Psychology, 83, 149–166. doi:10.1016/S0022-0965(02)00125-X

Ulrich, B. D., Thelen, E., & Niles, D. (1990). Perceptual determinants of action: Stair-climbing

choices of infants and toddlers. Advances in Motor Development Research, 3, 1–15.U.S. Consumer Product Safety Commission (2010).National electronic injury surveillance system

(NEISS). Retrieved from http://www.cpsc.gov/library/neiss.html

van der Meer, A. L. (1997). Visual guidance of passing under a barrier. Early Development and

Parenting, 6, 149–158.Wilmut, K., & Barnett, A. L. (2011). Locomotor behaviour of children while navigating through

apertures. Experimental Brain Research, 210, 185–194. doi:10.1007/s00221-011-2614-2Woollacott, M., & Shumway-Cook, A. (2002). Attention and the control of posture and gait: A review

of an emerging area of research.Gait & Posture, 16, 1–14. doi:10.1016/S0966-6362(01)00156-4Young, T., Torner, J., Schmitt, K., & Peek-Asa, C. (2011). Fall injury report (2002–2009 Iowa State

Trauma Registry Data). Des Moines, IA: Iowa Department of Public Health.

Received 21 April 2014; revised version received 13 November 2014


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Step by step: A microgenetic study of the development of ...csivc.csi.cuny.edu/Sarah.Berger/files/publications/BergerChinEtAl2015.pdf · coordinate different components of a plan