Chapter 2 - ML
Performance categories
- Performance outcome measures
- Define: measures that indicate the outcome or result of performing a motor skill
- Examples: distance someone walks; points per game for a basketball player; reaction time
- Limitation: RT, MT, and outcome measures do not reveal information about the musculoskeletal or neuromuscular system
- Performance production measures
- Define: measures that tell us how the neuromuscular and musculoskeletal system function during the performance of a motor skill
- Examples: EEG, EMG, kinematics
Performance outcome measures: Reaction Time (RT), Movement Time (MT), and Response Time
- Reaction Time (RT)
- Definition: the interval between the onset of a signal (stimulus) and the initiation of a response
- Formula (conceptual): RT = t{init} - t{stim}
- Classic diagram: Fig. 2.1 shows the sequence: Warning signal → foreperiod → Go signal → initiation of response → termination of response
- Foreperiod: the interval between the warning signal and the Go signal
- Go signal: cue to begin the response
- Movement Time (MT)
- Definition: the interval between the initiation of a movement and its completion
- Formula: MT = t{end} - t{init}
- Response Time
- Definition: total time interval involving both RT and MT
- Relationship: RT and MT are independent of each other (conceptual independence)
- Formula: RT_{total} = RT + MT
- Figure references
- Fig. 2.1: illustrates RT and MT events and time intervals
Types of RT situations (Fig. 2.2)
- Simple RT
- Example: sprinter hearing the signal to start running
- Choice RT
- Example: driving when a traffic signal changes (need to choose action)
- Discrimination RT
- Example: batter swinging at pitches in the strike zone (respond only to certain stimuli)
Error measures in motor performance
- Definition: the amount of error a person makes in performing a skill
- Types (overview): Absolute Error, Constant Error, and Variable Error
One-dimensional movement goals (1D)
- Absolute error (AE)
- Definition: the absolute difference between the actual performance on each repetition and the goal
- Formula (for a single trial): AE = |xi - x^| where xi is the observed value and x^ is the target value
- Constant error (CE)
- Definition: the signed deviation from the target; indicates amount and direction of error (bias)
- Purpose: measures systematic bias such as overshooting or undershooting
- Formula (mean across trials): $$CE = rac{1}{N} \