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Timing and accuracy of visually directed movements in children: control of direction and amplitude components
Insights
Children
Area of Science:
- Developmental psychology
- Motor control
- Human movement science
Background:
- Understanding the development of motor control in children is crucial for identifying developmental milestones and potential issues.
- Hand movement control involves complex coordination of direction and amplitude, which mature over childhood.
Purpose of the Study:
- To investigate the developmental trajectories of reaction time (RT), movement time (MT), and accuracy in children aged 6, 8, and 10 years.
- To differentiate the development of directional and amplitude control components in hand movements.
- To examine the role of visual feedback in motor control development.
Main Methods:
- Children aged 6, 8, and 10 performed hand movement tasks requiring distinct directional and amplitude control.
- Tasks were conducted with and without visual feedback of limb movement.
- Reaction times, movement times, and accuracy were measured.
Main Results:
- Reaction times decreased with age and were faster for directional than amplitude tasks.
- Movement times showed a non-linear pattern, peaking at age 8.
- Directional accuracy was consistent across ages, while amplitude accuracy varied, especially without visual feedback, with a dip at age 8.
- Visual feedback consistently improved accuracy.
Conclusions:
- Directional control develops earlier, primarily in the preparatory response stage.
- Amplitude control is more reliant on ongoing feedback and undergoes a longer developmental period, with age 8 being a critical phase for feedback-dependent control.
- With age, amplitude control increasingly utilizes feedforward processes.
Abstract:
The reaction times (RTs), movement times (MTs), and final accuracy of hand movements directed towards visual goals were measured in 6-, 8-, and 10-year-old children, using tasks in which direction and amplitude components of movement were distinctly required. The tasks were performed with and without visual feedback of the limb. RTs decreased with age, and were shorter in directional than in amplitude task, in all ages. MTs were the longest at age 8 in both tasks, equally short at ages 6 and 10 in the directional task, the shortest at age 10, and intermediate at age 6, when amplitude had to be regulated. In the amplitude task, the target distance generally affected MTs under both visual conditions, but to a lower degree at age 10 than in the two younger groups. Movement accuracy, which was in all cases higher with visual feedback, showed different developmental trends among the two spatial components: directional accuracy was not different among the three groups of age, whereas amplitude accuracy showed a nonmonotonic development in the nonvisual condition, with an increase between age 6 and age 10, and the lowest level at age 8. In the visual condition, amplitude accuracy did not change with age. The specification of direction seems therefore to predominantly load the preparatory stage of the response. Amplitude specification seems to be more dependent on on-going regulations and to undergo a longer and more complex development, with a critical period around age 8 when a greater propensity for a feedback-based control appears on the two components. With increasing age, amplitude tends to be specific to a greater extent by a feedforward process.