Motor Skill, Control, and Classification: Key Concepts and Measurements
jMovement, Intent, and Environment
Movement is intentional and goal-directed; it requires movements of joints or body segments executed through muscular contractions. Movement is our primary means of interacting with the environment, and all interaction is mediated through muscular contractions.
Distinguishing movement from abilities:
Abilities are traits shaped by growth, maturation, and genetics. They are enduring and difficult to improve or change (e.g., reaction time).
Movements are the actual motor actions; abilities influence how easily those movements can be improved, while skill is about how effectively we translate ability into reliable performance.
Abilities like simple reaction time are fairly hardwired; other reaction-time scenarios can be improved with practice, but such improvement relies on underlying motor skill.
Observing and measuring motor skills: a motor skill (e.g., throwing) can be achieved through different movement patterns, all producing the end result.
Guthrie’s definition of skill (1952):
(\text{Skill} = \text{the ability to bring about an end result with maximum certainty and minimum outlay of energy or time and energy}\
Three key elements:
Maximize the certainty of goal achievement (consistency in performance)
Minimize physical and mental effort required to achieve the goal
Ability to anticipate and adapt to what might happen in the environment; reduces unnecessary effort and improves efficiency
Anticipation and gaze behavior:
Experts tend to anticipate events better by extracting cues from the environment; their gaze behavior differs from novices, reflecting more efficient information extraction.
Once environmental information is perceived, you must decide what to do, where to do it, and when to do it to achieve the goal.
This decision-making process links to motor control and motor learning, helping account for and explain performance.
Example application: passing a soccer ball to a teammate requires selecting the correct response from sensory information and executing it at the right time.
Motor Control Concepts: Equivalence, Variability, and Persistence
Motor equivalence: when performing any action, there is an abundance of degrees of freedom (DOF). There are many possible movement patterns to achieve the same end result (e.g., reaching for a cut object: slow, fast, mirror-image, different trajectories).
Motor equivalence implies multiple valid solutions to the same goal; this flexibility underpins robust motor performance.
Motor variability: despite accuracy demands, actual movements vary slightly from trial to trial (e.g., swinging a ping-pong paddle; the motion is never exactly identical).
Principle of motor persistence: despite inherent variability, performers strive for consistent goal achievement over time; this is a major research challenge: how to sustain performance reliability in the face of variability.
Example: baseball check swing—experts can initiate the chain of events to cancel a response when necessary (e.g., when a pitch is off-target or distracting), illustrating how automaticity and inhibition operate under pressure.
Classification of Skills by Environment and Form
One-dimensional classification scale (environmental stability):
Closed skills: performed in a predictable, stable environment (e.g., indoors; weather not changing). You can plan a motor plan in advance before acting.
Open skills: performed in unpredictable environments (e.g., outdoor golf with wind changes); plans must adapt to changing conditions.
Impact: open vs closed affects decision-making, timing, and adaptability during performance.
Skill types by action structure:
Continuous skills: no well-defined beginning or end, often with rhythmic or cyclical elements (e.g., walking; gait cycle).
Serial skills: series of discrete actions linked together (e.g., performing a sequence of movements in order).
Discrete skills: not explicitly described in depth in the transcript, but often contrasted with continuous and serial as distinct start/stop actions.
Limitations of the 1D scale: Sean Teal (2000) argued the crude scale misses important distinctions; expanding the framework yields more precise categorization.
Teal’s expansion to 16 categories (2000):
Introduces two additional categories: object manipulation and body transport.
When considering whether objects or body parts are absent or present within a motor skill, the combination yields up to 16 possible categories when also accounting for environmental context.
Practical implications of expanded taxonomy:
Helps in designing targeted interventions and practice adaptations.
For example, object manipulation (e.g., sign language) can be analyzed with a 2D system to track changes and set new performance goals.
Brain, Measurement, and Performance Metrics
Brain involvement: different brain areas contribute to motor planning, execution, and error processing; understanding which areas are engaged can inform where improvements occur.
Performance measures: two broad categories are discussed:
Accuracy and error measures (e.g., standard errors, number of successful attempts)
Kinematic and production measures (e.g., displacement, velocity, acceleration)
Measurement can be conducted in one dimension (1D) or two dimensions (2D):
1D examples: simple line-tracking tasks, straight-line drawing
2D examples: complex drawing or spatial tasks requiring movement in a plane
Primary time-based measures in motor skill research:
Reaction time (RT): time from stimulus onset to movement initiation
Movement time (MT): time from movement initiation to completion
Response time (often used as a composite or alternative measure): generally considered in the context of the task (RT, MT, or a combination)
Important point: RT and MT are relatively independent; RT does not predict MT, and MT does not predict RT.
Experimental trial structure (typical design):
A warning signal or cue prompts readiness
A foreperiod (the waiting interval before the go signal) occurs
A go signal indicates when to execute the response
Foreperiod characteristics:
Fixed foreperiod: constant duration across trials
Variable foreperiod: duration varies to increase unpredictability and challenge timing preparation
Real-world relevance: timing and anticipation are critical in sports like sprinting (e.g., 100 m sprints) and hurdles, where precise timing and rapid response are essential.
Looking ahead: these timing concepts and measurement approaches are common across upcoming lectures and will be revisited with more depth.
Real-World Examples and Applications
Soccer passing: success depends on anticipating the opponent’s action and executing a pass at the right time to maximize chance of teammate reception.
Golf and weather: in a closed skill setting (predictable environment), you can plan ahead; in outdoor settings (open skill), you must adapt to wind and other changing conditions.
Baseball check swing: experts initiate cancellation of a movement when it becomes inappropriate or distracting, illustrating motor control, inhibition, and automaticity in action.
Sign language and object manipulation: using a 2D framework to track changes and set new goals enables targeted intervention planning and progress monitoring.
Connections to Foundations and Implications
Foundations in motor learning: skill is about reliable end-result achievement with efficient use of energy and time, underpinned by anticipation, planning, and adaptable execution.
Practical implications for training design:
Develop anticipatory skills by exposing learners to varied cues and ecological contexts
Balance variability and consistency to promote motor persistence while accommodating underlying variability
Use expanded classification to tailor practice tasks to specific skill contexts (object manipulation, body transport, environment type)
Ethical and practical considerations: focusing on improving consistency and efficiency has real-world implications for performance, safety, and rehabilitation; design of practice should respect individual differences in abilities and learning rates while leveraging motor skill principles.
Summary of Key Concepts (recap)
Distinction: movements (actions via muscles) vs abilities (innate/long-lasting traits)
Guthrie (1952): Skill = end result with maximum certainty and minimum energy/time
Three elements of skill: certainty, low effort, anticipation/plan for environment
Anticipation and gaze: experts vs novices; environment cues guide safe, timely actions
Motor equivalence: many valid movement solutions for the same end result
Motor variability: trial-to-trial movement differences; necessary to achieve consistent outcomes
Motor persistence: sustaining performance under variability; example in baseball checkswing inhibition
Skill classification by environment and form: closed vs open; continuous vs serial; Teal (2000) 16-category expansion including object manipulation and body transport
Measurement: RT, MT, and response time; 1D vs 2D tasks; standard errors and production measures like displacement, velocity, and acceleration
Foreperiod: fixed vs variable; impact on predictability and timing
Real-world relevance: sports performance, rehabilitation, and skill development depend on these principles