Timing Is Almost Everything: How Children Perceive and Act on Dynamic Affordances

Developmental changes in how pedestrians cross streets in single- vs. dual-lane traffic conditions

OBJECTIVE

Pedestrian injury is a leading contributor to childhood deaths. This study compared the crossing behaviors of children with adults when crossing in virtual single-lane vs. two-lane traffic conditions.

METHOD

Using a fully immersive virtual reality system, children 7-10 years and adults crossed streets with traffic in one lane (near lane) or in two lanes (near and far lane) with 0 offset so cars from opposing directions arrived at the child's crossing line at the same time. On each trial, pedestrians made a decision on when to cross and then completed the crossing, with measures of attention and crossing behaviors automatically recorded by the system as they did so.

RESULTS

In comparison to crossing a single lane of traffic, crossing two-lane roads increased injury risk for all pedestrians, though children experienced significantly greater risk than adults. Children predominantly crossed by stopping before entering the far lane, whereas adults showed greater synchronization of self-movement to traffic flow and more often crossed both lanes without stopping.

CONCLUSIONS

Children experience more high-risk outcomes than adults when crossing single-lane roads. Crossing two-lane roads elevates risk for pedestrians of both ages, though this risk is significantly greater for child than adult pedestrians. The predominant strategy used to cross two lanes of traffic shows significant developmental changes. Implications for injury prevention are discussed.

The Role of Walking Experience in the Emergence of Gait Harmony in Typically Developing Toddlers

The ability to walk without support usually develops in the first year of a typically developing toddler’s life and matures further in the following years. Mature walking is characterized by the correct timing of the different gait phases that make up a full gait cycle formed by stance, swing, and double support phases. The harmony of mature walking is given by a specific self-similar structure of the ratios between the durations of these phases (stride/stance, stance/swing, swing/double support), that in adults all converge to the golden ratio (phi, about 1.618). The aim of this longitudinal, prospective, experimental study was to investigate the evolution of this gait harmonic structure in the transition from supported to independent walking. In total, 27 children were recruited and recorded at various stages of locomotor development, ranging from neonatal stepping up to an independent walking experience of about six months. Differently from walking speed that progressively increased with age, the gait phase ratios started to converge to golden value only after the first independent steps, suggesting a relation to the maturation of the walking experience. The independent walking experience seems to represent a trigger for the evolution of a locomotor harmonic pattern in toddlers learning to walk.

Developmental differences across the lifespan in the use of perceptual information to guide action-based decisions

Perceptual information about unfolding events is important for guiding decisions about when and how to move in real-world action situations. As an exemplary case, road-crossing is a perceptual-motor task where age has been shown to be a strong predictor of risk due to errors in action-based decisions. The present study investigated age differences between three age groups (Children: 10-12 years old; Adults: 19-39 years old; Older Adults: 65 + year olds) in the use of perceptual information for selection, timing, and control of action when crossing a two-way street in an immersive, interactive virtual reality environment. Adults and children selected gaps to cross that were consistent with the use of a time-based information variable (tau), whereas older adults tuned less into the time-based variable (tau) to guide road-crossing decisions. For action initiation and control, children and adults also showed a strong ability to precisely time their entry with respect to the lead vehicle maximising the available time to cross and coordinating walking movements with the tail vehicle to ensure they were not on a collision course. In contrast, older adults delayed action initiation and showed difficulty coordinating self-movement with the approaching vehicle. This study and its results tie together age-based differences in the three components of action decision-making (selection, timing and control) within a unified framework based on perceptual information. The implications of these age-related differences in action decisions and crossing behaviours are discussed in the context of road safety.

Let's Cross the Next One: Parental Scaffolding of Prospective Control Over Movement

This investigation examined parental scaffolding of children's prospective control over decisions and actions during a joint perception-action task. Parents and their 6-, 8-, 10-, and 12-year-old children (N = 128) repeatedly crossed a virtual roadway together. Guidance and control shifted from the parent to the child with increases in child age. Parents more often chose the gap that was crossed and prospectively communicated the gap choice with younger than older children. Greater use of an anticipatory gap selection strategy by parents predicted more precise timing of entry into the gap by children. This work suggests that social interaction may serve as an important experiential mechanism for the development of prospective control over decisions and actions in the perception-action domain.

Motor Development Research: II. The First Two Decades of the 21st Century Shaping Our Future

In Part I of this series I, we looked back at the 20th 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 21st 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 20th century has evolved into a Developmental Systems approach in the 21st 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.