1. Chapter 8 Action Preparation
Concept: Performing voluntary, coordinated movement requires preparation of the motor control system

2. The Question of Interest in this Chapter
What does the motor control system do when we “get ready” to perform an action in a specific situation?
Action Action Action
Intention Initiation Termination
Preparation

3. Action Preparation Requires Time
Donders (1868), Dutch physician, began the research that demonstrated the need for time for the motor control system to prepare to produce an intended action
RT (reaction time) is the commonly used index of the preparation time required to produce action
Based on findings showing that RT is influenced by many performance situation and performer characteristics

4. Task and Situation Characteristics Influencing Preparation
Number of response choices
Hick’s Law:
RT increases logarithmically as the number of stimulus-response choices increases [See Fig. 8.1]
2. Predictability of the correct response choice
RT decreases as the predictability of the correct response choice increases

5. Task and Situation Characteristics Influencing Preparation, cont’d
3. Influence of the probability of precue correctness
Precue = an advance indication that a specific upcoming event will require a response
Faster RT if probability of precue correctness is higher than if probabilities of possible choices are equally possible
e.g. 2 choices = Right = 80% Left = 20% [compare with 50% – 50%]
Cost – benefit trade-off for biasing anticipated required response to the higher probability (if < 100%) – [See Fig. 8.2]

6. Task and Situation Characteristics Influencing Preparation, cont’d
Stimulus-response compatibility
RT decreases as the spatial relationship between a stimulus and its response increases
Stroop effect
Spatial arrangement of stimuli and their associated response mechanisms
e.g., Stove top example – see A Closer Look
Foreperiod length regularity
RT increases/decreases as a function of the length and the regularity of the length of the RT foreperiod
[i.e., interval between warning and go signals]

7. Task and Situation Characteristics Influencing Preparation, cont’d
Movement complexity
RT increases as amount of complexity of the action increases
First demonstrated by classic experiment by Henry and Rogers (1960) – See A Closer Look
Movement accuracy
RT increases as movement accuracy demands of the action increase
First demonstrated by evaluating RT results for Fitts’ tapping tasks with different Indexes of Difficulty (i.e. as MT increased, RT also increased)

8. Task and Situation Characteristics Influencing Preparation, cont’d
8. Repetition of a movement
9. Time between different responses to different signals
Delay of response to 2nd stimulus (signal)is called the psychological refractory period (PRP) – [See Figure 8.3]
Relate to a situation in sports involving a “fake” movement followed by the intended movement as the 2 stimuli and the other player’s responses as the 2 responses

9. Two Performer Characteristics Influencing Preparation
Alertness of the performer
Warning signal effect
Foreperiod length effect [See Fig. 8.4]
Vigilance effects
Attention focused on the signal vs. the movement
RT benefits more from focusing on the signal (e.g. sprint start in swimming)

10. Motor Control Events That Occur During Preparation
Postural preparation
Organization of movements needed for postural support
Anticipatory characteristic of movement activity involved in postural preparation
Flexible synergistic organization characteristic of postural movement preparation

11. Motor Control Events That Occur During Preparation, cont’d
Limb performance characteristics
e.g. Movement
Direction
Trajectory
End-point accuracy (i.e. for a ballistic movement)
Object control characteristics
Force control
End-state comfort position (i.e. hand’s final spatial position as initial position)

12. Motor Control Events That Occur During Preparation, cont’d
Sequences of movements
See research on piano playing as evidence
Spatial coding
Evidence from S-R compatibility research
Rhythmicity preparation
Preperformance rituals
See examples in Table 8.1
Research shows they appear to prepare relative timing of upcoming movements