In our tribute to Professor Michael Turvey, we have two parallel goals: 1) to highlight the scientific scope of Turvey’s impact on motor development; and, 2) to expose readers to papers that they may not have read but that might cast new light on age-old questions they confront in their current research on motor development. The paper is divided into two equal time periods. In Part 1, from 1975 to 1999, we trace the emergence and growth of Dynamic Systems/Ecological Realism (perception-action) paradigms. We explain how the existing paradigms in motor development research, the descriptive and information processing paradigms were, in part, replaced by new paradigms whose existence owes much to Michael Turvey and his colleagues. We suggest that this time period was one where Turvey had the most conceptual influence on the field. In Part 2, from 2000 to 2024, we describe how factors, including the emergence of two new paradigms in motor development research may have reduced Turvey’s direct influence. But we also note that there is still much research undertaken that builds off the bases of Dynamic Systems and Perception-Action Coupling approaches including research by Turvey and his students/colleagues. We end with the suggestion that the present generation of motor development researchers may have something to gain by re-/reading research from these perspectives regardless of whether it is directly from Professor Turvey’s pen or from those whom he influenced (or influenced him).

As part of the National Children's Study (NCS) comprehensive and longitudinal assessment of the health status of the whole child, scientific teams were convened to recommend assessment measures for the NCS. This manuscript documents the work of three scientific teams who focused on the motor, sensory, or the physical health aspects of this assessment. Each domain team offered a value proposition for the importance of their domain to the health outcomes of the developing infant and child. Constructs within each domain were identified and measures of these constructs proposed. Where available extant assessments were identified. Those constructs that were in need of revised or new assessment instruments were identified and described. Recommendations also were made for the age when the assessments should take place.

In 1981, George Brooks provided a review of the academic discipline of physical education and its emerging subdisciplines. Forty years later, the authors review how the field has changed from the perspective of one subdiscipline, motor development. Brooks’s text sets the scene with four chapters on motor development from leaders in the field, including G. Lawrence Rarick, to whom the book is dedicated. From this beginning, the paper describes the evolving scientific perspectives that have emerged since 1981. Clearly, from its past to the present, motor development as a scientific field has itself developed into a robust and important scientific area of study. The paper ends with a discussion of the grand challenges for kinesiology and motor development in the next 40 years.

Current methods to understand implicit motor sequence learning inadequately assess motor skill acquisition in daily life. Using fixed sequences in the serial reaction time task is not ideal as participants may become aware of the sequence, thereby changing the learning from implicit to explicit. Probabilistic sequences, in which stimuli are linked by statistical, rather than deterministic, associations can ensure that learning remains implicit Additionally, the processes underlying the learning of motor sequences may differ based on sequence structure. Here, the authors compared the learning of fixed and probabilistic sequences to randomly ordered stimuli using a modified serial reaction time task. Both the fixed and probabilistic sequence groups exhibited learning as indicated by decreased response time and variability. In the initial stage of learning, fixed sequences exhibited both online and offline gains in response time; however, only the offline gain was observed during the learning of probabilistic sequences. These results indicated that probabilistic structures may be learned differently from fixed structures and have important implications for our current understanding of motor learning. Probabilistic sequences more accurately reflect motor skill acquisition in daily life, offer ecological validity to the serial reaction time framework, and advance our understanding of motor learning.

The past is prologue, writes Shakespeare inThe Tempest. And there seems no better expression to capture the theme of my essay on searching the future of kinesiology in its recent past through my lens as a motor development scholar. Using the developmental metaphor of climbing a mountain amidst a range of mountains, the progressing stages of my development and that of kinesiology are recounted. Over the five-plus decades of my growth as an academic and that of kinesiology, I look for the antecedents and the constraints that shape our change and may shape the future of the field of motor development and kinesiology.

In 1989, Clark and Whitall asked the question, “What is motor development?” They were referring to the study of motor development as an academic research enterprise and answered their question primarily by describing four relatively distinct time periods characterized by changes in focus, theories or concepts, and methodology. Their last period was named the process-oriented period (1970–1989). In hindsight, it seems clear that their last period could be divided into two separate historical time periods: the information-processing period (1970–1982) and the dynamical systems period (1982–2000). In the present paper, we briefly revisit the first three periods defined by Clark and Whitall, and expand and elaborate on the two periods from 1970 to the turn of the century. Each period is delineated by key papers and the major changes in focus, theories or concepts, and methodology. Major findings about motor development are also described from some papers as a means of showing the progression of knowledge.

Perceptual-motor sequences can be learned quickly under distraction, often demonstrated by the mean reaction time (RT) change in a serial reaction time (SRT) task. However, any arbitrary mean RT can arise from one of many distinct trial-by-trial RT patterns. It is surprising that previous sequence learning studies have hinged only on the mean RT metrics while little is known about the distraction effect on its trial-by-trial processes. In an SRT task with or without distraction, we found that initially learning a fixed repeating sequence without distraction was expressed by a micro-online learning process where reaction time (RT) progressively improved within learning blocks as adults continuously performed the SRT task. Such online RT improvements, however, vanished when the SRT task was performed under distraction. Despite the detrimental effect of distraction on micro-online RT improvements, we observed offline enhancements in RT following rest intervals of 3 min that emerged to secure sequence learning under distraction. We reasoned that distraction may exert influence on the micro-online and offline learning by mediating the engagement of explicit and implicit memory. Given the offline RT change under distraction, a short rest between learning blocks may be a key player in early perceptual-motor sequence learning under distraction. We thus suggest that future studies investigating the distraction effect on sequence learning need to control the length of rest between learning blocks, while previous research with equivocal interpretations of the distraction effect failed to do so.

In Part I of this series I, we looked back at the 20 th century and re-examined the history of Motor Development research described in Clark & Whitall’s 1989 paper “What is Motor Development? The Lessons of History”. We now move to the 21 st century, where the trajectories of developmental research have evolved in focus, branched in scope, and diverged into three new areas. These have progressed to be independent research areas, co-existing in time. We posit that the research focus on Dynamical Systems at the end of the 20 th century has evolved into a Developmental Systems approach in the 21 st century. Additionally, the focus on brain imaging and the neural basis of movement have resulted in a new approach, which we entitled Developmental Motor Neuroscience. Finally, as the world-wide obesity epidemic identified in the 1990s threatened to become a public health crisis, researchers in the field responded by examining the role of motor development in physical activity and health-related outcomes; we refer to this research area as the Developmental Health approach. The glue that holds these research areas together is their focus on movement behavior as it changes across the lifespan.

Motor development research has had a rich history over the 20th century with a wide array of scientists contributing to a broad and deep body of literature. Just like the process of development, progress within the field has been non-linear, with rapid periods of growth occurring after the publication of key research articles that changed how we conceptualized and explored motor development. These publications provided new ways to consider developmental issues and, as a result, ignited change in our theoretical and empirical approaches within the field of motor development and the broader field of developmental psychology. In this paper, we outline and discuss six pioneering studies that we consider significant in their impact and in the field’s evolution, in order of publication: Halverson, 1931; Wild, 1938; Gibson & Walk, 1960; Connolly, Brown, & Bassett, 1968; Thelen & Fisher, 1982; Thelen & Ulrich, 1991. We have limited this review to empirical papers only. Together, they offer insight into what motor development research is, where it came from, why it matters, and what it has achieved.

This protocol describes a modified serial reaction time (SRT) task used to study implicit motor sequence learning. Unlike the classic SRT task that involves finger-pressing movements while sitting, the modified SRT task requires participants to step with both feet while maintaining a standing posture. This stepping task necessitates whole body actions that impose postural challenges. The foot-stepping task complements the classic SRT task in several ways. The foot-stepping SRT task is a better proxy for the daily activities that require ongoing postural control, and thus may help us better understand sequence learning in real-life situations. In addition, response time serves as an indicator of sequence learning in the classic SRT task, but it is unclear whether response time, reaction time (RT) representing mental process, or movement time (MT) reflecting the movement itself, is a key player in motor sequence learning. The foot-stepping SRT task allows researchers to disentangle response time into RT and MT, which may clarify how motor planning and movement execution are involved in sequence learning. Lastly, postural control and cognition are interactively related, but little is known about how postural control interacts with learning motor sequences. With a motion capture system, the movement of the whole body (e.g., the center of mass (COM)) can be recorded. Such measures allow us to reveal the dynamic processes underlying discrete responses measured by RT and MT, and may aid in elucidating the relationship between postural control and the explicit and implicit processes involved in sequence learning. Details of the experimental set-up, procedure, and data processing are described. The representative data are adopted from one of our previous studies. Results are related to response time, RT, and MT, as well as the relationship between the anticipatory postural response and the explicit processes involved in implicit motor sequence learning.

In this chapter, we ask two questions. First, can the study of the perception-action system across time offer a useful model for understanding motor development? Second, can the study of the perception-action system in children with developmental coordination disorder (DCD) inform our understanding of atypical as well as typical motor development? We begin by describing the dynamical systems perspective and a control-theoretic approach that together provide the conceptual framework for our paradigms, methodology, and interpretation of our experiments. Our experimental strategy has been to perturb one or more sensory systems and observe the effect on the motor system. The majority of the chapter explains how we employed two principal perturbation strategies: (1) removing or adding a static source of sensory information believed to be salient to the task at hand and (2) enhancing a dynamic source of sensory information either implicitly or explicitly. These strategies were employed in three different action systems: posture; rhythmic interlimb coordination, and goal-directed reaching and drawing. After synthesizing our findings, we conclude by addressing the original questions and offering future directions. In brief, we consider that perception-action coupling is an underlying mechanism/foundation/constraint of motor development in the sense that the ongoing processing of sensations and the planning and execution of movements are how the brain produces goal-directed movements. Therefore, a better understanding of how this coupling changes or adapts over time has much to offer as to how motor behavior develops across the lifespan, both typically and atypically.

How we understand the emergence and development of motor behavior and skillfulness has itself developed over the last 50 years. In reflecting on the history of motor development, it is important to recognize that these ‘reflections’ are much like the painter’s “pentimento.” That is, the ‘canvas’ we paint today of what our science was decades ago is actually a painting with many layers—each representing where our views have changed along the journey. I do not “repent” with these reflections, as suggested by the term, pentimento, but rather I seek to bring a developmental perspective to our scientific inquiries into motor development with an element of a revisionist’s approach. What were the key discoveries and the seminal papers that influenced our canvas of motor development that we view today? Almost three decades ago, we (Clark & Whitall, 1989) outlined an historical framework for the field of motor development. Today, we can look back at that framework and the ensuing science and consider where we have been and what we have learned and ask: What does the pentimento of our motor development canvas reveal?

Background: Estimates of the prevalence of developmental coordination disorder range from 1.7% to 19%, raising concerns about the discriminative ability of the Movement Assessment Battery for Children (MABC). Aims: We compared MABC performance of children aged 4–12 years from the USA and Brazil. We aimed to examine: a) the prevalence of motor impairment across countries; b) age band and sex differences across countries; c) the test's ability to discriminate and predict motor impairment; and d) to identify the discriminating capacity of each MABC subtest. Methods: Children (n=1055) from Brazil and the USA were included in the present study. MABC cut-off points (typical development: above 15%, at risk: 6–15%; developmental coordination disorder: 0–5%) and discriminant analyses were used. Findings: Prevalence of probable developmental coordination disorder (24.1%) and at risk (16.2%) was higher in the Brazilian sample. Higher prevalence of probable developmental coordination disorder was observed among girls and among children aged 11–12 years old for the Brazilian sample and among boys and among children aged 9–12 years old for the American sample. Differences in scores across countries were only observed for children with typical development in manual dexterity and balance skills. The MABC discriminant functions were able to predict the classification of children into typical development, at risk, and probable developmental coordination disorder. The manual dexterity subtest was the strongest predictor for both samples, whereas the ball skills subtest was the weakest predictor. Conclusions: Differences for prevalence were found across countries. American results were similar with current estimates relative to incidence and gender; for Brazilian children, prevalence was near three times higher and more persistent among girls. Overall, in both countries the motor difficulties demonstrated by children with probable and at risk of developmental coordination disorder were similar for all tasks. The MABC showed predictably and discriminant capacity in the identification of children with probable and at risk developmental coordination disorder in both countries.

AIM To better understand the neural and performance factors that may underlie developmental coordination disorder (DCD), and implications for a multi-component account. METHOD A systematic review of the experimental literature published between June 2011 and September 2016 was conducted using a modified PICOS (population, intervention, comparison, outcomes, and study type) framework. A total of 106 studies were included. RESULTS Behavioural data from 91 studies showed a broad cluster of deficits in the anticipatory control of movement, basic processes of motor learning, and cognitive control. Importantly, however, performance issues in DCD were often shown to be moderated by task type and difficulty. As well, we saw new evidence of compensatory processes and strategies in several studies. Neuroimaging data (15 studies, including electroencephalography) showed reduced cortical thickness in the right medial orbitofrontal cortex and altered brain activation patterns across functional networks involving prefrontal, parietal, and cerebellar regions in children with DCD than those in comparison groups. Data from diffusion-weighted magnetic resonance imaging suggested reduced white matter organization involving sensorimotor structures and altered structural connectivity across the whole brain network. INTERPRETATION Taken together, results support the hypothesis that children with DCD show differences in brain structure and function compared with typically developing children. Behaviourally, these differences may affect anticipatory planning and reduce automatization of movement skill, prompting greater reliance on slower feedback-based control and compensatory strategies. Implications for future research, theory development, and clinical practice are discussed.

Timing control, such as producing movements at a given rate or synchronizing movements to an external event, has been studied through a finger-tapping task where timing is measured at the initial contact between finger and tapping surface or the point when a key is pressed. However, the point of peak force is after the time registered at the tapping surface and thus is a less obvious but still an important event during finger tapping. Here, we compared the time at initial contact with the time at peak force as participants tapped their finger on a force sensor at a given rate after the metronome was turned off (continuation task) or in synchrony with the metronome (sensorimotor synchronization task). We found that, in the continuation task, timing was comparably accurate between initial contact and peak force. These two timing events also exhibited similar trial-by-trial statistical dependence (i.e., lag-one autocorrelation). However, the central clock variability was lower at the peak force than the initial contact. In the synchronization task, timing control at peak force appeared to be less variable and more accurate than that at initial contact. In addition to lower central clock variability, the mean SE magnitude at peak force (SEP) was around zero while SE at initial contact (SEC) was negative. Although SEC and SEP demonstrated the same trial-by-trial statistical dependence, we found that participants adjusted the time of tapping to correct SEP, but not SEC, toward zero. These results suggest that timing at peak force is a meaningful target of timing control, particularly in synchronization tapping. This result may explain the fact that SE at initial contact is typically negative as widely observed in the preexisting literature.