chapter 6

SPMD 3710: Motor Learning - Action Preparation

New Mexico State University
nmsu.edu

Chapter Overview

The chapter focuses on Action Preparation, highlighting various phases and factors that influence motor responses. This includes the concepts of intention, preparation, initiation, and termination of movements. Several aspects related to preparation time and reaction time (RT) are discussed in detail.

Phases of Action Preparation

Action preparation consists of several key phases:

  • Intention: The cognitive decision to perform a movement.

  • Preparation: The period during which the motor system readies itself for action.

  • Initiation: The moment the action begins, which can be influenced by various factors.

  • Termination: The conclusion of the movement once the action is completed.

Preparation Time and Reaction Time

  • Preparation Time: The motor control system requires time to prepare for the production of an intended action, a concept first elaborated by Donders in 1868.

  • Reaction Time (RT): Defined as the time required to produce a voluntary movement. RT is crucial in understanding how various performance situations and individual characteristics can influence motor responses. Factors that can modify RT include:

    • Performance Situations: Changes in context can affect the necessary RT.

    • Performer Characteristics: Individual differences such as skill level, fatigue, and anxiety can cause variability in RT.

Task and Situational Characteristics Affecting Reaction Time

  1. Number of Response Choices: The RT increases as the number of potential responses increases.

    • Hick’s Law: Expressed as RT = b imes ext{log}_2 (N + 1); where (N) is the number of choices and (b) is a constant that depends on the task. This law was formulated by Hyman in 1953.

  2. Predictability of the Correct Response: RT decreases with increased predictability of the correct answer.

    • Pre-cuing Paradigm: Advanced information is provided about an upcoming event that necessitates a response. Focus and attention are critical components in utilizing this information effectively.

  3. Probability of Pre-cue Correctness: An increased probability of a correct pre-cue leads to decreased RT if the likelihood exceeds 50%. This reflects a cost-benefit trade-off where performers weigh the advantages of correct pre-cues against errors.

  4. Stimulus-Response Compatibility: RT is influenced by how well the spatial relationship between a stimulus and a response aligns, impacting the ease of response.

    • Design Considerations: The arrangement of stimulus and response can be designed to enhance compatibility, exemplified through the Stroop Effect.

The Stroop Effect

  • The Stroop Effect reveals the interference that occurs in reaction time due to conflicting information. For example, naming the color of the ink in which color names are written leads to significantly longer RTs. Different word-color combinations (e.g., the word 'RED' printed in blue ink) illustrate the cognitive delay caused by the competing stimuli.

Fore Period Length Regularity

  • Fore Period Length Regularity: Refers to the interval between a warning and the go-stimulus. Greater regularity in this interval results in shorter RTs due to the predictability of the timing.

Measurement of Reaction Times

  • Table 1: Means and Medians of Winning Reaction Times

    • Sportsman:

    • Mean: Lower Rounds 0.086s; Upper Rounds 0.062s; All Rounds 0.079s.

    • Median: Lower Rounds 0.031s; Upper Rounds 0.047s; All Rounds 0.056s.

    • Pro:

    • Mean: Lower Rounds 0.052s; Upper Rounds 0.046s; All Rounds 0.050s.

    • Median: Lower Rounds 0.037s; Upper Rounds 0.032s; All Rounds 0.035s.

    • Super Pro:

    • Mean: Lower Rounds 0.028s; Upper Rounds 0.028s; All Rounds 0.028s.

    • Median: Lower Rounds 0.019s; Upper Rounds 0.018s; All Rounds 0.019s.

    • All Classes:

    • Mean: Lower Rounds 0.052s; Upper Rounds 0.044s; All Rounds 0.050s.

    • Median: Lower Rounds 0.033s; Upper Rounds 0.028s; All Rounds 0.031s.

Movement Complexity and Reaction Time

  • Movement Complexity: The reaction time tends to increase with the complexity of the movement.

    • A study by Henry & Rogers (1960) highlighted that additional elements in a task require more time to organize movement control.

    • Method: The study required participants to respond to a light using three different movements:

      • Lift finger (150ms).

      • Lift finger and grasp ball (195ms).

      • Lift finger and hit several targets (208ms).

    • This increasing RT illustrates how movement complexity demands greater cognitive and motor resources.

Psychological Refractory Period

  • Repetition of a Movement: This is influenced by the time taken between responses to different signals. The phenomenon of the Psychological Refractory Period indicates a delay of response to the second stimulus following an initial response, which is especially relevant in sports where performers must quickly switch between actions.

Performer Characteristics

  • Alertness: Several factors impact an individual's alertness including:

    • Warning Signal Effect: The efficacy of cueing and signaling.

    • Fore Period Length: The duration of anticipation can affect RT.

    • Vigilance Effect: The need to maintain alertness over time is critical, particularly in roles such as military and law enforcement where responses must be preserved even during periods of infrequent stimuli.

  • Attentional Focus: The participant's focus can vary between sensory and motor aspects. A study by Christina (1973) revealed that when focusing on sensory initiation, movements were executed about 20ms faster than when focusing on motor aspects.

  • Environmental Factors: External conditions such as sleep deprivation, stress, and anxiety can adversely affect reaction times, alongside lifestyle choices such as caffeine intake, which may enhance alertness but could also lead to jitteriness.

Preparation and Motor Control

  • Control Events in Movement Preparation: The control mechanisms involved during the preparation stage include:

    • Fractionating RT: Breaking down response times into components for better analysis.

    • Postural Preparation: Adjustments needed in posture to facilitate movement execution, highlighting the intricate relationship between posture and action.

  • Limb Performance Preparation: This encompasses the preparation needed for limb movements focusing on direction, trajectory, and accuracy.

  • Object Control Preparation: Considerations for preparing to manipulate objects, emphasizing necessary force application and achieving a comfortable end-state, which relates to how comfortable the performer will be at completion of the task.

  • Movement Sequences: Short sequences of movements can be prepared in advance, signifying an important aspect of coordination and planning for effective performance.

  • Rhythmicity Preparation: Involves performance rituals, commonly observed in sports such as basketball, to enhance readiness and focus prior to action.