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TSpace Research Repository tspace.library.utoronto.ca
Independent Development of Imagination
and Perception of Fitts’ Law in Late Childhood and
Adolescence
Emma Yoxon and Timothy N. Welsh
Version Post-print/accepted manuscript
Citation
(published version)
Yoxon, E., & Welsh, T. N. (2018). Independent Development
of
Imagination and Perception of Fitts' Law in Late Childhood and
Adolescence. Journal of motor behavior, 50(2), 166-176.
Publisher’s Statement This is an Accepted Manuscript of an
article published by Taylor
& Francis in Journal of Motor Behavior on 6-23-2017,
available online: http://www.tandfonline.com/
10.1080/00222895.2017.1327408
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This is an Author’s Original Manuscript of an article published
by Taylor & Francis in The
Journal of Motor Behaviour on 23/06/2017, available online:
http://www.tandfonline.com/10.1080/00222895.2017.1327408
Independent Development of Imagination and Perception of Fitts’
Law in Late Childhood
and Adolescence
Emma Yoxon and Timothy N. Welsh
Faculty of Kinesiology & Physical Education, Centre for
Motor Control
University of Toronto, Toronto, ON, Canada
RUNNING HEAD: Imagination and Perception Development
KEY WORDS: development, mental chronometry, motor imagery,
perception
http://www.tandfonline.com/10.1080/00222895.2017.1327408
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Imagination and Perception Development 2
Abstract
Data demonstrating Fitts’ law in action imagination and
perception suggests that these processes
share a common mechanism. Research has revealed that children
demonstrate Fitts’ speed-
accuracy trade-off in imagined actions, and that imagined
movement time (MT) becomes more
similar to actual MT as age increases. The relationship between
execution, imagination and
perception has yet to be evaluated in children. The current
study assessed how imagined and
perceived MT related to actual MT in children and adolescents.
It was found that imagined MT
was longer than execution MT across all the age ranges.
Perception MT was lower than
execution MT for children and was more consistent with execution
MT for adolescents. These
results reflect potential mechanistic differences in action
imagination and perception.
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Imagination and Perception Development 3
Introduction
When humans attempt a motor skill, they may first imagine the
action and its outcome.
Accordingly, it is thought that the human brain can simulate the
internal components of actions
without actually producing any external movements. For instance,
many athletes use
visualization or mental practice as a training tool to mentally
take themselves through a routine
or a game without the need for actual physical practice. It is
thought that such simulation and
mental practice is an effective training tool because it has
been demonstrated that when an
individual imagines themselves performing an action, they
activate a neural network that is
similar to the one that is involved in actual movement execution
(Hétu et al., 2013; Jeannerod,
2001; Munzert, Lorey, & Zentgraf, 2009). In this sense, it
is thought that the brain is effectively
simulating the internal components of movement by activating the
neural codes that generate
action offline without leading to overt movement.
This concept of action code-based simulation has been extended
beyond the explicit
imagination of action and has been implicated as a more implicit
mechanism that unifies the
processes that help us perceive and understand our own actions
and the actions of others
(Jeannerod, 2001). In action observation and possibility
judgements, for example, it is thought
that the neural simulation of action allows an individual to map
an observed movement onto their
own motor system and capabilities, allowing the individual to
make accurate judgements about
how possible a given movement is to complete (Chandrasekharan,
Binsted, Ayres, Higgins, &
Welsh, 2012; Grosjean, Shiffrar, & Knoblich, 2007; Welsh,
Wong, & Chandrasekharan, 2013).
These processes are often referred to as “action perception”.
Furthermore, because of the
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Imagination and Perception Development 4
important role that motor simulations play in perceiving and
understanding actions, there has
been growing research in how simulation processes emerge in
childhood. Importantly, the
mirroring of others’ actions via motor simulations is thought to
play an important role in how
young children learn to link gestures and movements with their
meanings and effects (Paulus,
Hunnius, & Bekkering, 2013; Paulus, Hunnius, Vissers, &
Bekkering, 2011a, 2011b).
Neural simulation of action
Evidence for neural motor simulation in action imagination and
perception has been
broadly drawn from neurophysiological and behavioural studies
that have reported that the motor
system is active in and constrains action imagination and
perception. First, neuroimaging studies
have clearly demonstrated that when participants imagine
themselves performing movements,
there is activation of a neural network that overlaps with that
of actual execution (e.g., Stippich,
Ochmann, & Sartor, 2002; see Hétu et al., 2013 for a
meta-analysis and comprehensive review).
Additionally, many studies have employed transcranial magnetic
stimulation (TMS) to study
changes in the excitability of the corticospinal tract while
individuals imagine themselves
performing actions. These studies find that when individuals
imagine themselves performing an
action, there is a quantifiable increase in excitability of the
corticospinal tract, which suggests
that the motor system is active during action imagination (e.g.,
Clark, Tremblay, & Ste-Marie,
2004; see Munzert et al., 2009 for review). Similar
neurophysiological results have been found
for action perception, wherein previous research has
demonstrated that various aspects of the
motor system are active when an individual is making judgements
about a movement (Eskenazi,
Rotshtein, Grosjean, & Knoblich, 2012). Importantly, it has
also been demonstrated that there is
considerable overlap in the cortical areas shown to be active in
action imagination, perception
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Imagination and Perception Development 5
and execution, suggesting that these processes are in fact part
of a singular representational
domain (Grèzes & Decety, 2001).
Behaviourally, evidence for common neural substrates underlying
action execution,
imagination and perception (and therefore motor simulation) has
been drawn from
demonstrations of the temporal similarities between these three
processes. Specifically, many
previous studies have demonstrated the presence of Fitts’ law
(Fitts, 1954) in imagined and
perceived movement times (MTs) of cyclical aiming movements.
Fitts’ law is a mathematical
equation that describes the relationship between the lowest MTs
possible to maintain accuracy
and the difficulty of the manual aiming movements. It can be
described by the formal equation:
MT = a + b(ID), where “a” and “b” are constants relating to an
individual’s base MT and their
unit increase in MT as a function of the index of difficulty
(ID), respectively. The ID component
of this equation can be further broken down as ID = log 2(2A/W),
where A is the movement
amplitude between a pair of targets (centre-to-centre distance
between the targets) and W is the
width of the targets. Essentially, in a task that requires an
individual to touch back and forth
between a target pair, the shortest possible MT in which the
person can maintain accuracy will
increase as a function of both movement amplitude and target
width (the index of movement
difficulty - ID).
Decety and Jeannerod (1995) first demonstrated the relationship
between speed-accuracy
trade-offs in imagination in a study of the walking paths of
their participants. The researchers
asked individuals to imagine themselves walking towards door
openings that varied in their
distance to the participant and in the width of the opening.
Critically, participants demonstrated
Fitts’ law in their imagined walking paths. Specifically,
participants’ imagined walking paths
were slower when the door opening was narrower and the walking
path was longer. Since this
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Imagination and Perception Development 6
original experiment, this result has been corroborated and
extended to manual movements
similar to Fitts’ original aiming task (Sirigu et al., 1995;
Wong, Manson, Tremblay, & Welsh,
2013; Young, Pratt, & Chau, 2009; Yoxon, Tremblay, &
Welsh, 2015).
This principle of speed-accuracy trade-offs has also been
demonstrated in action
possibility judgements. In these studies, individuals are asked
to decide on the possibility of an
aiming movement being executed accurately when it is shown at a
given speed. It has been
repeatedly shown that participants choose MTs that are
consistent with Fitts’ law; that is, the
lowest MT they judge as being possible to accurately complete
the movement increases as the ID
of the observed movement increases (Chandrasekharan et al.,
2012; Grosjean et al., 2007; Welsh
et al., 2013; Wong et al., 2013). Together, the results of these
studies demonstrate that there is
congruency in the temporal aspects of executed, imagined, and
perceived action which suggests
again that these processes share a common representational
network and involve similar neural
mechanisms.
Action simulation in children
In recent years, there has also been interest in how action
simulation emerges in
childhood. Developmental motor imagery research is similar to
research that has been done in
adults in that it has focused on the increasing congruence of
actual and imagined MTs across
childhood development (Gabbard, 2009). The results of this
research suggest that simulation
processes are likely formed in early childhood as evidenced by
the presence of Fitts’ law in the
imagined movements of young children aged approximately seven
years; although this
relationship is more evident in older children and
adolescents(Caeyenberghs, Tsoupas, Wilson,
& Smits-Engelsman, 2009; Caeyenberghs, Wilson, van Roon,
Swinnen, & Smits-Engelsman,
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Imagination and Perception Development 7
2009). Cross-sectional studies have also revealed that imagined
MTs become closer to actual
execution MTs as a child ages, becoming closer to the congruence
between these measures seen
in adults as children approach adolescence, suggesting that
there is ongoing refinement of action
simulation processes in childhood (approximately six-to-eleven
years) (Caeyenberghs, Wilson, et
al., 2009; Smits-Engelsman & Wilson, 2013). Some studies
have also demonstrated
developmental differences in the temporal consistency of action
imagination between
adolescents and adults (Choudhury, Charman, Bird, &
Blakemore, 2007a, 2007b) although
studies with larger age spans of six to nineteen years
(Caeyenberghs, Wilson, et al., 2009; Smits-
Engelsman & Wilson, 2013) suggest that these changes are
more subtle compared to the changes
seen from early to late childhood and just prior to
adolescence.
Interestingly, while developmental aspects of motor imagery have
been relatively well
characterized, there has been little focus in developmental
changes in the perception and
possibility judgment of human movement. There is some evidence
that the motor system is likely
engaged in the imitative processes that are central to motor
learning in infancy and toddlerhood
(Paulus et al., 2011b) as well as evidence of action
co-representation (the representation of an
observed action in one’s own motor system) in early childhood
(Marshall, Bouquet, Thomas, &
Shipley, 2010; Saby, Marshall, Smythe, Bouquet, & Comalli,
2011). Although the results of this
previous research again demonstrate that motor simulation
processes are likely intact at a young
age, it remains largely unknown how perceptions of action change
as a child’s own motor
repertoire changes.
Therefore, the purpose of the current experiment was to evaluate
changes in the temporal
similarity of action possibility judgements with actual MT as a
function of age and to assess
differences or similarities in the developmental trajectories of
action possibility judgements and
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Imagination and Perception Development 8
motor imagery. To address this purpose, an experimental paradigm
employing action possibility
judgements similar to that of Grosjean, Shiffrar and Knoblich
(2007) and a mental chronometry
paradigm similar to those of Wong et al. (2013) and Yoxon et al.
(2015) was used. Children
between the ages of seven and sixteen, as well as a control
group of adults executed aiming
movements to target pairs with varying accuracy demands.
Imagination and perception tasks
employed the same target pairs. It was hypothesized that MTs in
action perception, imagination
and execution would conform to Fitts’ law, as action simulation
processes should be initially
developed before the age of seven. Of greater theoretical
relevance, specific predictions involved
comparisons across the different tasks. If action perception and
imagination share a common
representational domain and action simulation is an underlying
mechanism for both action
possibility judgements and imagination, then these processes
should develop in similar ways.
Specifically, MTs in both action imagination and action
possibility judgements should approach
actual execution MTs with age. If this is not the case, it is
possible that these processes may have
different underlying mechanisms that develop independently of
each other.
Methods
Participants
Thirty-four children between the ages of seven and sixteen (24
Male, 10 Female) and 11
young adults (2 Male, 9 Female, Mean Age = 22.4) were recruited
for the study. Two male
children participants were removed because it was disclosed to
the experimenter subsequent to
testing that they were diagnosed with unspecified developmental
and learning disabilities that
may have impacted motor skills and comprehension of task
instructions. All other participants
were reported to be typically developing and had normal or
corrected-to-normal vision.
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Imagination and Perception Development 9
Handedness was collected using a modified version of the
Edinburgh Handedness Questionnaire.
All participants, with the exception of two children, were right
handed. One of these participants
was left-handed and the other reported no distinct preference
for activities of daily living. All
participants provided informed assent and their parents or
guardians provided informed consent
prior to testing. All procedures were approved by the University
of Toronto Research Ethics
Board.
Study Design and Tasks
The design of the present study was based on previous studies
(Chandrasekharan et al.,
2012; Grosjean et al., 2007; Wong et al., 2013). Participants
completed action execution,
imagination and perception tasks. The execution task was always
performed first, followed by
the remaining two tasks. This order was specifically chosen
because previous research has
demonstrated the effect of experience on perceived and imagined
MTs (Chandrasekharan et al.,
2012; Wong et al., 2013; Yoxon et al., 2015). Specifically, it
has been found that perceived and
imagined MTs more accurately reflect actual execution MTs after
task-specific experience. This
increased consistency may reflect experience-based refinement of
internal action simulations and
occurs because participants are able to link the perceptual
effects of an action with the actual
motor experience during practice. These more closely linked
representations of action and effect
can then facilitate imaginations that are more temporally
similar to actual execution MTs.
Because of the observed benefit of experience on perception and
imagination, the execution task
was performed first to: 1) avoid any variance in the data due to
differences in task experience
that a random or completely counterbalanced order would have
provided; and 2) give each
individual experience with the execution of the task thereby the
best capability of demonstrating
accurate imagination and perception. Essentially, the execution
task was performed prior to the
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Imagination and Perception Development 10
other two tasks to equate all individuals on task-specific
experience. Any observed
developmental differences in perception and imagination tasks
can therefore be more closely
equated to differences in age and not differences in previous
experience with similar tasks.
Although the execution was always performed first, the
imagination and perception tasks
were counterbalanced to ensure there were no effects of
execution experience just prior to
completing either of these tasks. To confirm that this was not
the case prior to the main analysis,
the effect of order in these two tasks was assessed by carrying
out a 2 (task: imagination,
perception) by 2 (order: imagination first, perception first)
mixed ANOVA with repeated
measures on the task variable on imagined and perceived MTs.
Although there was a main effect
of task, F(1,41) = 96.097, p < .01, there was no significant
effect of order, F(1,41) = .048, p =
.827, or task by order interaction, F(1,41) = .551, p = .462.
These results indicate that there was
no significant effect of task order in relation to imagined or
perceived MTs.
Participants were tested individually, under the direct
supervision of the experimenter. In
each of the tasks, data collection only proceeded when the
experimenter had confirmed that the
participant understood the task. The overall time in testing was
between 30 and 45 minutes.
All tasks were performed using a touch screen monitor (3M™
MicroTouch™ Display,
473.8mm (W) x 296.1 mm (H)). In all of the tasks, six sets of
two targets varying in target width
and movement amplitude were used. The targets were one of two
widths: 2.5 cm or 3.5 cm. The
centre-to-centre measurement (movement amplitude) for a given
movement context was one of
7.5 cm, 15 cm or 30 cm for the 2.5 cm target. For the 3.5 cm
target, the centre-to-centre
measurement was one of 10.5 cm, 21 cm or 42 cm. These
combinations generated two target
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Imagination and Perception Development 11
pairs for each of the IDs: 2.6, 3.6 and 4.6. The combination of
target width and movement
amplitude remained consistent throughout a specific trial.
Execution Task. Participants were seated comfortably in front of
a table upon which the
touch screen monitor rested. In a given trial, they were
presented with one of the six target pairs.
Beginning with the index finger of their dominant hand on the
right side target, participants were
asked to perform ten continuous pointing movements as quickly
and accurately as possible
between the two targets. One movement was from the right to the
left target and the next from
the left to the right target. They were told that they must move
as quickly as possible but that
they must also try to always land “on the line” (i.e., within
the target). This sequence was
repeated three consecutive times for each target pair for a
total of 30 movements per target
condition. Prior to the experimental trials, the experimenter
gave the task instructions and
participants experienced three practice trials, during which
they had the opportunity to ask the
experimenter questions about the task and the experimenter could
confirm their understanding of
the task demands.
The order of the target combinations was randomized. The
accuracy (spatial coordinates
of screen contact) and the time to complete the movements were
recorded, by the custom
program, which also displayed the stimuli for analysis offline.
A single mean MT was calculated
for each of the six combinations of target width and movement
amplitude. Erroneous trials where
there was clearly either computer or human error (a touch
recorded on the same side of space
two times in a row or where the touch screen failed to record a
touch) were removed prior to
calculation of the mean MT for each target pair. Additionally,
touches that fell beyond 35 px
(approximately 1 cm) of the target were considered errors and
were also removed at this point.
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Imagination and Perception Development 12
These procedures resulted in the removal of approximately 4.3%
(erroneous trials) and 0.7%
(error) of the individual touches in the execution data
overall.
Imagination Task. The experimental set up was consistent with
that of the execution
task. In a given trial, participants were presented with one of
the six target pairs. They began
with the index finger of their dominant hand on the right side
target and imagined executing ten
pointing movements between the targets as quickly and accurately
as they could execute the
movements in real time. Similar to the execution task,
participants were asked to imagine their
finger moving as quickly as it did in “real life” and to imagine
themselves always landing “on
the line” (i.e., on the target). Participants were asked to
perform the imagination from an internal
(first person) perspective. They were instructed to lift their
finger off the monitor (a maximum of
about 5 cm) for the time required to imagine the movement and
then place their finger back onto
the monitor after imagining the movements. They were also
instructed that the finger lift should
occur when they imagined their finger lifting off for the first
time and the placing of the finger
back onto the monitor should occur when they imagined their
finger returning to the right side
target on the tenth movement. This sequence was repeated three
times for each target pair for a
total of 30 imagined movements.
Prior to experimental trials, participants experienced three
practice trials during which
they had the opportunity to ask the experimenter questions about
the task and the experimenter
could confirm the participant’s understanding. The order of the
target pairs was randomized. The
total time required to complete the imagination (from finger
lift to contact with the touch screen)
was recorded for analysis. A mean MT was calculated for each of
the target pairs and this mean
time was derived by dividing the total imagination time by ten
to provide a mean MT for each
target pair in a given trial. Trials where there was either
computer or human error (where the
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Imagination and Perception Development 13
touch screen failed to register a touch or the participant
admitted to improperly performing the
task) were flagged throughout testing and were removed prior to
analysis. This process resulted
in the removal of approximately 2% of the imagination data.
Perception Task. Participants were seated as in the other two
tasks. In the perception
task, the touch screen monitor presented two digital photographs
of the hand of a young adult
woman performing the execution task from an internal or
first-person perspective: the first
picture was of a person with their right index finger on the
right side target and the second
picture was of the finger on the left side target (see Figure
1). These photos were presented
alternately to create the apparent motion of the model in the
photographs moving between the
two targets. In a given trial, the photos were presented at one
of eleven different stimulus onset
asynchronies (SOAs) ranging between 120 ms and 520 ms. The SOA
remained constant within a
trial and the trial ended when the participant’s response was
recorded. Participants were asked to
judge if it is possible for them to maintain accuracy while
moving at the shown speed.
Specifically, they were told that the task was to decide if it
was possible or impossible to move
as fast as the hand is moving and still be able to land “on the
line” (i.e., to land accurately on the
targets). They were told to pick the best answer (possible or
impossible) for their own
performance. Participants would verbally tell the experimenter,
“yes” or “no”, if they thought the
movement was possible or impossible to move at the given MT,
respectively.
Prior to testing, participants were shown 3 practice trials, two
of which represented the
extremes of the SOA/target pair combinations (a high difficulty
with the fastest possible
movement and a low difficulty with the slowest possible
movement) and the other was a target
pair with ID = 2.6 at SOA = 200 ms to represent a trial that was
at neither of the previously
presented extremes. During these practice trials, the
experimenter asked the participants
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Imagination and Perception Development 14
questions to confirm their understanding. For example, the
experimenter would ask the
participant why they thought a particular movement was possible
or impossible. During this
time, the experimenter also answered any questions the
participants had. After confirming their
understanding of the task, participants completed one block of
perceptual judgments consisting
of 66 trials (6 target combinations x 11 SOAs). For each of the
6 target pairs, the point at which
participants changed their responses from impossible to possible
(this point was the point along
the spectrum of SOAs where the participant answered “yes” twice
in a row) was determined and
the SOA at this point was considered to be the minimum MT
perceived to be possible for a given
combination of target width and amplitude (or ID). This process
generated one data point for
each of the 6 target pairs. A similar type of task has been used
several times in adult studies to
assess how individuals perceive an observed action
(Chandrasekharan et al., 2012; Eskenazi et
al., 2012; Grosjean et al., 2007; Welsh et al., 2013).
Therefore, the current method is consistent
with previous work, but was modified for use with children.
Specifically, a single block of trials
(as opposed to multiple blocks of trials) was performed to
maintain a relatively short time in
testing, to balance task demands boredom and fatigue,
particularly in younger children.
Results
Prior to statistical analysis, child participants were initially
divided into two experimental
groups to facilitate analysis of differences between younger
children (seven to eleven, n = 18)
and adolescents (12 to 16, n = 14). This division was chosen at
this age because it has been
shown to be a critical point for corticospinal maturation (Yeo,
Jang, & Son, 2014), motor skill
acquisition (Sugden & Wade, 2013) as well as motor imagery
development (Caeyenberghs,
Wilson, et al., 2009; Smits-Engelsman & Wilson, 2013).
Specifically, this age seems to delineate
all three of these processes in that there is more rapid
development up until approximately eleven
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Imagination and Perception Development 15
or twelve years, followed by more subtle developmental changes
in corticospinal maturation,
motor skill acquisition and motor imagery ability from this age
onward.
Fitts’ Law
To determine if MTs in each group and task conformed to Fitts’
speed accuracy trade-off,
a linear regression was calculated between group mean MT for
each of the six combinations of
target width and amplitude and ID. For all groups and all tasks,
MT was significantly correlated
with ID, confirming the presence of Fitts’ law in all groups and
tasks (Figure 2). For equations
and statistics, see Table 1.
Group Differences
An analysis of variance was conducted to further examine within-
and between-group
differences between execution, imagination and perception task
MTs. Because MTs were found
to conform to Fitts’ speed-accuracy trade-off, a single mean MT
was calculated per participant
for each task. These mean MTs were submitted to a 3 (task:
execution, imagination, perception)
by 3 (group: child, adolescent, adult) mixed ANOVA with repeated
measures on the first factor.
Mauchly’s test indicated that the assumption of sphericity had
been violated (2 (2) = 12.42, p <
.01). Therefore, degrees of freedom were corrected using
Greenhouse-Geisser estimates of
sphericity (ε = .79). All post-hoc analyses were conducted using
Tukey’s HSD.
The analysis revealed a significant effect of task, F(1.57,
62.85) = 71.30, p < .001, where
imagined MTs (M = 483 ms) were significantly higher than those
for perception (M = 302 ms)
and execution (M = 364 ms), and perception MTs were
significantly lower than those for
execution and imagination. There was also a significant effect
of group, F(2,40) = 5.07, p < .05,
where MTs averaged across all tasks for the child group (M = 416
ms) were significantly higher
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Imagination and Perception Development 16
than those of the adult group (M = 351 ms). There was no
significant difference in overall MT
between the children and adolescents, although there was a trend
towards lower overall MTs for
the older group (M = 366 ms). Finally, there was a significant
group by task interaction, F(3.14,
62.85) = 3.73, p < .05. Post-hoc analysis of the interaction
showed that in the child group, there
were significant differences between the mean MTs of all tasks,
with MTs in the perception task
being the lowest and MTs in the imagination task the highest
(see Figure 3). In the adolescent
group and adult groups, the mean MT for imagination was
significantly higher than the mean
MT for both perception and execution, but there were no
significant differences between
perception and execution. Between the groups, there were no
significant differences between
MTs for the execution or perception tasks, although the
difference in execution times between
the younger child group and the other two groups approached
significance. In the imagination
task, the child group had significantly higher MTs than the
older group and the adult group.
The relationship between age and simulation congruency
To assess the relationship between congruency of action
simulation processes (the degree
to which perception and imagination MTs reflect actual execution
MTs) and age (i.e., how these
measures change with age), difference scores between mean
imagination and execution and
mean perception and execution MTs were calculated for each
participant. This analysis only
included the child participants. Pearson’s correlation
coefficient and linear regressions were
calculated for the correlation between difference scores for
imagination and age as well as the
correlation between difference scores for perception and age. It
was found that difference scores
for perception were significantly and positively correlated with
age (r = .71, p < .001, y = 20.16 x
– 299.40) such that perception MTs approach actual MTs as age
increased (Figure 4-A). In
contrast, there was no significant correlation between the
difference scores for imagination and
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Imagination and Perception Development 17
age (r = .005, p = .98, y = 0.19 x + 121.60), suggesting that
these differences were more stable
across the age range (Figure 4-B).
Discussion
The aim of the current study was to quantify the relationship
between action execution,
imagination and perception in children and adolescents and to
describe how these relationships
change as a function of age. Typically developing children
between the ages of seven and sixteen
and young adults completed three tasks, execution, imagination
and perception (action
possibility judgement), which involved continuous aiming
movements to the same six target
pairs. Overall, the MTs for each of these tasks for each group
of participants increased as a
function of the difficulty (ID) of the aiming movement and
therefore conformed to Fitts’ law.
The critical finding, however, was that MTs selected in the
action possibility judgements task
became increasingly congruent with actual execution MTs as age
increased, whereas imagined
MTs did not exhibit a similar developmental change. These
results are discussed over the
following sections as they relate to neural simulation in action
imagination and perception.
Fitts’ law in imagination and perception
Overall, the presence of Fitts’ law in action perception and
imagination across all age
groups demonstrates that action simulation processes are intact
and at least partially developed
by the age of seven. This result is in line with the findings of
previous motor imagery research,
where the consensus is that the ability to effectively engage in
motor imagery is present by
approximately seven years of age (Gabbard, 2009). This finding
is also consistent with previous
action observation and imitation research in infancy which has
implicated a motor simulation
mechanism for imitation and observational learning (Paulus et
al., 2013, 2011a, 2011b). It is
-
Imagination and Perception Development 18
also consistent with the work of Marshall et al. (2010)and Saby
et al. (2011) who demonstrated
that children’s movement trajectories change when observing the
incongruent movement
trajectory of another person (i.e., a motor contagion effect).
In sum, the result that both imagined
and perceived MTs followed Fitts’ speed-accuracy trade-off is
additional evidence for motor
system activation in the imagination and perception of movement
in children.
The relationship between age and action imagination
In contrast to past work, the current experiment found no
age-related differences in the
congruency between imagined and executed MTs. Specifically,
although action imagination
times were longest in the youngest children, the difference
between real and imagined MTs did
not change as a function of age. Instead, imagined MTs were
consistently greater than actual
execution MTs. Although it is not entirely clear why this
difference emerges, it should be noted
that the overestimation of imagined MTs is very common for this
type of aiming task (see Wong
et al., 2013; Young et al., 2009; Yoxon et al., 2015).
Additionally, because the younger
children’s actual execution MTs were numerically (but not
significantly) longer than those of the
other groups, the small decrease in imagined MT from the younger
to the older group does not
represent a developmental change in the temporal congruency of
action imagination. Moreover,
the correlational analysis presented here demonstrates that
there is not a consistent change in the
way imagined MTs approached actual MTs as a function of age.
Therefore, the ability to imagine
the temporal aspect of movements (i.e., the congruency between
real and imagined movements)
does not seem to change from later childhood into
adolescence.
This result may be related to the nature of developmental
changes in motor imagery in
late childhood. Previous studies (Caeyenberghs, Wilson, et al.,
2009; Smits-Engelsman &
-
Imagination and Perception Development 19
Wilson, 2013) included a large number of children in early
childhood. It is this early age range
(five to eight years) that seem to have the largest
discrepancies between real and imagined MT
(Caeyenberghs, Wilson, et al., 2009; Molina, Tijus, & Jouen,
2008; Skoura, Vinter, &
Papaxanthis, 2009; Smits-Engelsman & Wilson, 2013). It is
possible, therefore, that these
differences in younger children under the age of seven (where it
is thought that motor imagery
processes are largely developed, see Gabbard, 2009; Molina et
al., 2008) contributed to the age-
related differences seen in previous studies. Relatedly, a
recent study that evaluated age-related
imagery ability using a self-report questionnaire developed for
use with children found no age-
related differences in self-reported ease of imagery in children
aged seven to twelve years
(Martini, Carter, Yoxon, Cumming, & Ste-Marie, 2016).
Therefore, it is likely that age-related
changes in the temporal congruency of motor imagery did not
emerge in the current experiment
because developmental differences in action imagination are more
subtle at the age range used in
the current study.
Recent task experience may have also played an important role in
the consistency of
motor imagery ability. In the current study, all children
executed the pointing task before
imagination and perception tasks. This experience, however, was
not provided in past studies.
For example, the study of Caeyenberghs, Tsoupas and colleagues
(2009) included many tasks
that were counterbalanced across participants, meaning that
execution experience may have
occurred at various times relative to the imagination task.
Smits-Engelsman and Wilson (2013)
only used imagination and execution tasks but these were also
counterbalanced so that half the
participants began with imagined movements. Recent work has
demonstrated the effect of task
experience on the accuracy of imagination and perception of
continuous aiming movements
(Chandrasekharan et al., 2012; Wong et al., 2013; Yoxon et al.,
2015) suggesting that task
-
Imagination and Perception Development 20
experience may lead to more accurate imagined and perceived MTs.
Essentially, it is thought that
experience with a given task can generate a more accurate
representation of an action and its
associated perceptual effects – leading to more accurate
imagination and perception of
movement. Therefore, it is also possible that the very recent
task experience in the current study
may have led to more accurate perception-action representations,
particularly in the younger
children who may lack in general motor experience compared to
older children and adolescents.
However, if this were the case, similar effects would be
expected in action perception, because
this process would also be affected by experience (as in
Chandrasekharan et al., 2012).
Therefore, although the lack of age-related changes in action
imagination (in comparison to the
results of other studies) may be related to recent task
experience, it is more likely that this effect
is due to more subtle developmental differences in this task,
from late childhood to adolescence.
The relationship between age and action perception
In contrast to the results of action imagination, the difference
between actual MTs and
MTs selected as possible in the perception task decreased as a
function of age. Specifically,
younger children were shown to have a larger disparity between
actual execution MTs and
perceived MTs than adolescents, indicating that the younger
participants overestimated their
abilities (shorter estimated MTs mean more efficient
performance). These action possibility
judgements were more congruent with actual MTs in the
adolescents, indicating that the
discrepancy and overestimation of their abilities relative to
their actual abilities decreased as a
function of age. Developmental research of risk taking and
injury proneness in children would
suggest that this overestimation of abilities in younger
children is not uncommon (Sandseter &
Kennair, 2011). It is known, for instance, that children
regularly engage in “risky play” or
situations that provide a thrilling experience (such as jumping
from heights and moving at high
-
Imagination and Perception Development 21
speeds) as part of normal cognitive and motor development. These
behaviours are likely related
to the abilities of younger children to estimate their abilities
and the consequences of their
actions (Sandseter & Kennair, 2011). Specifically, children
are more likely to overestimate their
abilities in tasks beyond their abilities than adults (Plumert,
1995).
Although these abilities may also be influenced by social and
individual factors, there is
also an evident developmental component as older children and
adolescents seem to be able to
more accurately characterize their abilities than younger
children (Plumert & Schwebel, 1997). It
should be noted here that the body of literature on children’s
ability to estimate what they are
capable of performing goes beyond what is very briefly discussed
here. For example, authors
have examined the individual and developmental differences that
impact a child’s risk perception
for a given task (e.g.,Schwebel & Bounds, 2003; Schwebel
& Plumert, 1999, see Sandseter &
Kennair, 2011 for review). Critically, however, whereas the body
of literature on children’s
assessment of ability focuses mainly on how children perceive
their own abilities when they are
presented with a given task, the current study asks children to
make a judgement on a movement
that they are actively observing. To the authors’ knowledge,
this is the first time that action
perception and possibility judgements have been studied in this
way. For this reason, although
developmental differences in ability estimation and risk taking
are likely related to the results of
the current study, these initial conclusions should be
considered preliminary and with some
caution. Future more dedicated and expansive work is needed to
assess the interpretation of the
results and conclusion.
The current study’s results could also be accounted for by
typical perceptual-motor
development. From late childhood to adolescence (the age range
used in the current study),
children begin to engage in more complex activities that present
new challenges (e.g. engaging in
-
Imagination and Perception Development 22
more open motor skills). These new challenges, coupled with
neurophysiological development,
are thought to preclude improvements in perception-action
coupling (Sugden & Wade, 2013).
Essentially, more experience and a larger motor repertoire
afford older children and adolescents
stronger associations between actions and their effects,
allowing them to better predict the
outcomes of their actions. This effect is evidenced by
experimental work demonstrating the
increased ability of older children to intercept objects
(Chohan, Verheul, Van Kampen, Wind, &
Savelsbergh, 2008) and to plan safe movement trajectories
(Chihak et al., 2010; Plumert &
Schwebel, 1997). In the context of the current experiment,
weaker perception-action coupling in
younger children could have led to less accurate action
possibility judgements in that an inability
to link the perceptual effects of an action (observed by the
participants) with a specific motor
pattern could hinder a child’s ability to make effective
predictions about the action’s possibility.
Consequently, children may be choosing faster or “riskier”
perceived MTs, as they often do in
more ecologically valid situations, because they cannot
adequately predict the true consequences
of the observed action. Although the presence of Fitts' law in
their perception (as well as
imagination) MTs suggests that action simulation occurs and is
intact, underdeveloped
perception-action coupling may have interfered with the
transformation of perception-to-action.
This underdevelopment may have also interfered with the ability
to relate the motor simulation to
an accurate choice of possible MT.
Another related important consideration is that action
possibility judgements, in
comparison to action execution and imagination, rely on the
comparison between what is
observed and what is simulated as well as a determination of a
threshold for possibility. The
factor associated with determining the threshold of what is
possible or not has been addressed to
a certain degree earlier in the discussion of risk-taking. That
is, it is possible that there is a
-
Imagination and Perception Development 23
greater distinction between actual and perceived MTs because the
younger children have a
relatively low threshold for that they think is possible for
them to perform - there is an
overestimation of their capabilities because of a low
threshold/cut-off for what is possible. The
factor that might have led to challenges for the youngest group
was the comparison between the
observed movements on the screen and the simulation. That is,
the presentation of a young adult
arm in the perception task may have led to challenges in
self-other matching in younger children.
Past research has demonstrated that children may more readily
represent the actions and hands of
younger (i.e. age matched) children (Liuzza, Setti, &
Borghi, 2012; Marshall et al., 2010).
Therefore, it is possible that the participants in the current
study were unable to fully represent
the adult hand, or were unable to match this representation of
"other" on the screen with
representation of the “self” in the simulation. Younger
children, therefore, may have been unable
to produce a possibility judgement that is congruent with their
own capabilities, but is more
congruent with the assumed abilities of the observed hand. The
results of Welsh et al. (2013)
suggest that adults can successfully make judgements for people
with different capabilities
(notably between child and adult performers) and are not driven
to make the judgements for the
person they are observing (child vs. adult model). In this
context, it might be instructive to note
that perceived MTs for each group were consistent with each
other (i.e., perceived MTs for the
youngest group were not different from those of the adolescents
and the adults). Because the
present work was the first to target this question of action
perception and possibility judgements
using this approach, it was not possible to anticipate this
distinction for the youngest group and
so a child vs. adult model comparison was not included in the
design. Overall, it is not clear if
the differences between perception and execution MTs for the
youngest group were due to an
inappropriately low threshold for distinguishing between what is
possible and impossible, a
-
Imagination and Perception Development 24
relatively poor ability to distinguish and compare between
“self” and “other”, or some other
mechanism. Future research that more specifically addresses
these issues (perhaps as in
Chandrasekharan et al., 2012, and Welsh et al., 2013) is
needed.
Conclusions
The critical finding of the current study was that the
developmental trajectories of
imagination and perception from late childhood to adolescence
are different. Between the ages of
seven and sixteen years, the temporal congruency between real
and imagined MTs remained
relatively stable, whereas the congruency between MTs selected
in the action possibility
judgement task and real MTs increased as age increased. This
result stands in contrast to the
prediction that the temporal congruence in these two tasks
should increase in a similar way due
to their shared mechanisms. Therefore, it is likely that there
are differences in the underlying
cognitive and neural mechanisms of action imagination and
perception. Results compliant with
Fitts’ law in both tasks and the stability of action imagination
suggest that neural motor
simulation is developed by late childhood. Further, results
compliant with Fitts’ law in the action
possibility judgement task indicate that, at some level, an
action simulation process is intact.
However, the underestimation of MTs in the action possibility
judgements may be due to
differences in an additional self-other, perception-action
matching processes, or threshold
setting; all of which are necessary to form accurate judgements.
Specifically, action possibility
judgements involve the comparing or relating of observed action
effects to one’s own
representation of the task. Therefore, although children may be
able to neurally simulate actions,
their ability to effectively use these simulations to predict
movement outcomes likely continues
to develop into adolescence.
-
Imagination and Perception Development 25
Acknowledgements
This research was supported by grants from the Natural Sciences
and Engineering Research
Council and the Ontario Ministry of Research and Innovation to
T.N.W.
-
Imagination and Perception Development 26
References
Caeyenberghs, K., Tsoupas, J., Wilson, P. H., &
Smits-Engelsman, B. C. M. (2009). Motor
imagery development in primary school children. Developmental
Neuropsychology, 34(1),
103–21. doi:10.1080/87565640802499183
Caeyenberghs, K., Wilson, P. H., van Roon, D., Swinnen, S. P.,
& Smits-Engelsman, B. C. M.
(2009). Increasing convergence between imagined and executed
movement across
development: evidence for the emergence of movement
representations. Developmental
Science, 12(3), 474–83. doi:10.1111/j.1467-7687.2008.00803.x
Chandrasekharan, S., Binsted, G., Ayres, F., Higgins, L., &
Welsh, T. N. (2012). Factors that
affect action possibility judgements: recent experience with the
action and the current body
state. Quarterly Journal of Experimental Psychology, 65(5),
976–93.
doi:10.1080/17470218.2011.638720
Chihak, B. J., Plumert, J. M., Ziemer, C. J., Babu, S.,
Grechkin, T., Cremer, J. F., & Kearney, J.
K. (2010). Synchronizing self and object movement: how child and
adult cyclists intercept
moving gaps in a virtual environment. Journal of Experimental
Psychology. Human
Perception and Performance, 36(6), 1535–1552.
doi:10.1037/a0020560
Chohan, A., Verheul, M. H. G., Van Kampen, P. M., Wind, M.,
& Savelsbergh, G. J. P. (2008).
Children’s use of the bearing angle in interceptive actions.
Journal of Motor Behavior,
40(1), 18–28. doi:10.3200/JMBR.40.1.18-28
Choudhury, S., Charman, T., Bird, V., & Blakemore, S.-J.
(2007a). Adolescent development of
motor imagery in a visually guided pointing task. Consciousness
and Cognition, 16(4),
886–96. doi:10.1016/j.concog.2006.11.001
Choudhury, S., Charman, T., Bird, V., & Blakemore, S.-J.
(2007b). Development of action
representation during adolescence. Neuropsychologia, 45(2),
255–62.
doi:10.1016/j.neuropsychologia.2006.07.010
-
Imagination and Perception Development 27
Clark, S., Tremblay, F., & Ste-Marie, D. (2004).
Differential modulation of corticospinal
excitability during observation, mental imagery and imitation of
hand actions.
Neuropsychologia, 42(1), 105–112.
doi:10.1016/S0028-3932(03)00144-1
Decety, J., & Jeannerod, M. (1995). Mentally simulated
movements in virtual reality: does
Fitts’s law hold in motor imagery? Behavioural Brain Research,
72(1-2), 127.
Eskenazi, T., Rotshtein, P., Grosjean, M., & Knoblich, G.
(2012). The neural correlates of Fitts’s
law in action observation: An fMRI study. Social Neuroscience,
7(1), 30–41.
doi:10.1080/17470919.2011.576871
Fitts, P. M. (1954). The information capacity of the human motor
system in controlling the
amplitude of movement. Journal of Experimental Psychology,
47(6), 381–391.
Gabbard, C. (2009). Studying action representation in children
via motor imagery. Brain and
Cognition, 71(3), 234–9. doi:10.1016/j.bandc.2009.08.011
Grèzes, J., & Decety, J. (2001). Functional anatomy of
execution, mental simulation,
observation, and verb generation of actions: a meta-analysis.
Human Brain Mapping, 12(1),
1–19.
Grosjean, M., Shiffrar, M., & Knoblich, G. (2007). Fitts’s
Law Holds for Action Perception.
Psychological Science, 18(2), 95–99.
Hétu, S., Grégoire, M., Saimpont, A., Coll, M.-P., Eugène, F.,
Michon, P.-E., & Jackson, P. L.
(2013). The neural network of motor imagery: an ALE
meta-analysis. Neuroscience and
Biobehavioral Reviews, 37(5), 930–49.
doi:10.1016/j.neubiorev.2013.03.017
Jeannerod, M. (2001). Neural Simulation of Action: A Unifying
Mechanism for Motor
Cognition. NeuroImage, 14(1), S103–S109.
doi:10.1006/nimg.2001.0832
Liuzza, M. T., Setti, A., & Borghi, A. M. (2012). Kids
observing other kids’ hands: Visuomotor
priming in children. Consciousness and Cognition, 21(1),
383–392.
doi:10.1016/j.concog.2011.09.015
-
Imagination and Perception Development 28
Marshall, P. J., Bouquet, C. a., Thomas, A. L., & Shipley,
T. F. (2010). Motor contagion in
young children: Exploring social influences on perception-action
coupling. Neural
Networks, 23(8-9), 1017–1025.
doi:10.1016/j.neunet.2010.07.007
Martini, R., Carter, M. J., Yoxon, E., Cumming, J., &
Ste-Marie, D. M. (2016). Development
and validation of the Movement Imagery Questionnaire for
Children (MIQ-C). Psychology
of Sport and Exercise, 22, 190–201.
doi:10.1016/j.psychsport.2015.08.008
Molina, M., Tijus, C., & Jouen, F. (2008). The emergence of
motor imagery in children. Journal
of Experimental Child Psychology, 99(3), 196–209.
doi:10.1016/j.jecp.2007.10.001
Munzert, J., Lorey, B., & Zentgraf, K. (2009). Cognitive
motor processes: the role of motor
imagery in the study of motor representations. Brain Research
Reviews, 60(2), 306–326.
Paulus, M., Hunnius, S., & Bekkering, H. (2013).
Neurocognitive mechanisms underlying social
learning in infancy: Infants’ neural processing of the effects
of others' actions. Social
Cognitive and Affective Neuroscience, 8(7), 774–779.
doi:10.1093/scan/nss065
Paulus, M., Hunnius, S., Vissers, M., & Bekkering, H.
(2011a). Bridging the gap between the
other and me: the functional role of motor resonance and action
effects in infants’ imitation.
Developmental Science, 14(4), 901–910.
doi:10.1111/j.1467-7687.2011.01040.x
Paulus, M., Hunnius, S., Vissers, M., & Bekkering, H.
(2011b). Imitation in infancy: rational or
motor resonance? Child Development, 82(4), 1047–57.
doi:10.1111/j.1467-
8624.2011.01610.x
Plumert, J. M. (1995). Relations between children’s
overestimation of their physical abilities and
accident proneness. Developmental Psychology, 31(5), 866–876.
doi:10.1037/0012-
1649.31.5.866
Plumert, J. M., & Schwebel, D. C. (1997). Social and
temperamental influences on children’s
overestimation of their physical abilities: links to accidental
injuries. Journal of
Experimental Child Psychology, 67(3), 317–37.
doi:10.1006/jecp.1997.2411
-
Imagination and Perception Development 29
Saby, J. N., Marshall, P. J., Smythe, R., Bouquet, C. a., &
Comalli, C. E. (2011). An
investigation of the determinants of motor contagion in
preschool children. Acta
Psychologica, 138(1), 231–236.
doi:10.1016/j.actpsy.2011.06.008
Sandseter, E. B. H., & Kennair, L. E. O. (2011). Children’s
risky play from an evolutionary
perspective: The Anti-phobic effects of thrilling experiences.
Evolutionary Psychology,
9(2), 257–284.
Schwebel, D. C., & Bounds, M. L. (2003). The Role of Parents
and Temperament on Children’s
Estimation of Physical Ability: Links to Unintentional Injury
Prevention. Journal of
Pediatric Psychology, 28(7), 505–516.
doi:10.1093/jpepsy/jsg041
Schwebel, D. C., & Plumert, J. M. (1999). Longitudinal and
Concurrent Relations among
Temperament, Ability Estimation, and Injury Proneness. Child
Development, 70(3), 700–
712. doi:10.1111/1467-8624.00050
Sirigu, A. ., Cohen, L., Duhamel, J. R., Pillon, B., Dubois, B.,
Agid, Y., & Pierrot-Deseilligny,
C. (1995). Congruent unilateral impairments for real and
imagined hand movements.
NeuroReport, 6, 997–1001.
Skoura, X., Vinter, A., & Papaxanthis, C. (2009). Mentally
simulated motor actions in children.
Developmental Neuropsychology, 34(3), 356–367.
doi:10.1080/87565640902801874
Smits-Engelsman, B. C. M., & Wilson, P. H. (2013).
Age-related changes in motor imagery from
early childhood to adulthood: probing the internal
representation of speed-accuracy trade-
offs. Human Movement Science, 32(5), 1151–62.
doi:10.1016/j.humov.2012.06.006
Stippich, C., Ochmann, H., & Sartor, K. (2002). Somatotopic
mapping of the human primary
sensorimotor cortex during motor imagery and motor execution by
functional magnetic
resonance imaging. Neuroscience Letters, 331(1), 50–54.
doi:10.1016/S0304-
3940(02)00826-1
Sugden, D., & Wade, M. G. (2013). Typical and atypical motor
development. London: Mac
Keith Press.
-
Imagination and Perception Development 30
Welsh, T. N., Wong, L., & Chandrasekharan, S. (2013).
Factors that affect action possibility
judgments: The assumed abilities of other people. Acta
Psychologica, 143(2), 235–244.
doi:10.1016/j.actpsy.2013.04.003
Wong, L., Manson, G. A., Tremblay, L., & Welsh, T. N.
(2013). On the relationship between the
execution, perception, and imagination of action. Behavioural
Brain Research, 257, 242–
252.
Yeo, S. S., Jang, S. H., & Son, S. M. (2014). The different
maturation of the corticospinal tract
and corticoreticular pathway in normal brain development:
diffusion tensor imaging study.
Frontiers in Human Neuroscience, 8(August), 1–6.
doi:10.3389/fnhum.2014.00573
Young, S. J., Pratt, J., & Chau, T. (2009). Misperceiving
the speed-accuracy tradeoff: Imagined
movements and perceptual decisions. Experimental Brain Research,
192(1), 121–132.
doi:10.1007/s00221-008-1563-x
Yoxon, E., Tremblay, L., & Welsh, T. N. (2015). Effect of
task-specific execution on accuracy
of imagined aiming movements. Neuroscience Letters, 585,
72–6.
doi:10.1016/j.neulet.2014.11.021
-
Imagination and Perception Development 31
Tables and Figures
Figure 1. An example of the pictures that were displayed in the
perception task. Images 1 (hand
on the right side target) and 2 (hand on the left side target)
were alternated at a range of
stimulus onset asynchronies (SOAs) to create the apparent motion
of the hand.
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Imagination and Perception Development 32
Table 1. Fitts’ law equations and statistical analysis for the
linear regressions calculated between
MT and ID for each of the tasks and groups.
Children Aged 7-11 Equation
𝑴𝑻 = 𝒂 + 𝒃 ∙ 𝑰𝑫 R2 p
Execution MT = 116.1 + 81.13(ID) .98 .0002
Imagination MT = 324.0 + 59.99(ID) .95 .0009
Perception MT = 25.78 + 75.56(ID) .99
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Imagination and Perception Development 33
Figure 2. Linear regressions between index of difficulty (ID)
and movement time for each of the
three tasks, for each of the three experimental groups.
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Imagination and Perception Development 34
Figure 3. Mean imagined MTs for each of the execution,
perception and imagination tasks.
Asterisks indicate significant (Tukey’s HSD, p < .05, CV =
79.9) within group
differences between the tasks.
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Imagination and Perception Development 35
Figure 4. Difference scores between imagination and execution
(A) and perception and
execution (B) as a function of age. Note: This analysis includes
only child participants.
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