Chapter 8Chapter 8

Action PreparationAction PreparationConcept: Performing voluntary, coordinated movement requires preparation of the motor control system

The Question of Interest The Question of Interest in this Chapterin this Chapter

What does the motor control system do What does the motor control system do when we “get ready” to perform an action when we “get ready” to perform an action in a specific situation?in a specific situation?

ActionAction ActionAction ActionAction

IntentionIntention InitiationInitiation TerminationTermination

Preparation

Action Preparation Requires TimeAction Preparation Requires Time

Donders (1868), Dutch physician, began the Donders (1868), Dutch physician, began the research that demonstrated the need for time research that demonstrated the need for time for the motor control system to prepare to for the motor control system to prepare to produce an intended actionproduce an intended action

RT (reaction time) is the commonly used index RT (reaction time) is the commonly used index of the preparation time required to produce of the preparation time required to produce actionaction

–Based on findings showing that RT is influenced by Based on findings showing that RT is influenced by many performance situation and performer many performance situation and performer characteristics characteristics

Task and Situation Characteristics Task and Situation Characteristics Influencing PreparationInfluencing Preparation1.1. Number of Number of

response choicesresponse choices–Hick’s Law:Hick’s Law:

RT increases RT increases logarithmically as the logarithmically as the number of stimulus-number of stimulus-response choices response choices increases increases [[See Fig. 8.1See Fig. 8.1]]

2.2. Predictability of the Predictability of the correct response correct response choicechoice

•RT decreases as the RT decreases as the predictability of the predictability of the correct response choice correct response choice increasesincreases

Task and Situation Characteristics Task and Situation Characteristics Influencing Preparation, cont’dInfluencing Preparation, cont’d3.3. Influence of the probability of precue Influence of the probability of precue

correctnesscorrectness•PrecuePrecue = an advance indication that a specific = an advance indication that a specific

upcoming event will require a responseupcoming event will require a response•Faster RT if probability of precue correctness is Faster RT if probability of precue correctness is

higher than if probabilities of possible choices are higher than if probabilities of possible choices are equally possibleequally possible

•e.ge.g. 2 choices = Right = 80% Left = 20% . 2 choices = Right = 80% Left = 20% [compare with [compare with 50% – 50%]50% – 50%]

•Cost – benefit trade-off for biasing anticipated Cost – benefit trade-off for biasing anticipated required response to the higher probability (if < 100%) – required response to the higher probability (if < 100%) – [[See Fig. 8.2See Fig. 8.2]]

Task and Situation Characteristics Task and Situation Characteristics Influencing Preparation, cont’dInfluencing Preparation, cont’d4.4. Stimulus-response compatibilityStimulus-response compatibility

• RT decreases as the spatial relationship between a RT decreases as the spatial relationship between a stimulus and its response increasesstimulus and its response increases

• Stroop effectStroop effect• Spatial arrangement of stimuli and their associated Spatial arrangement of stimuli and their associated

response mechanismsresponse mechanisms e.ge.g., Stove top example – see A Closer Look ., Stove top example – see A Closer Look

5.5. Foreperiod length regularityForeperiod length regularity–RT increases/decreases as a function of the length RT increases/decreases as a function of the length

and the regularity of the length of the RT foreperiodand the regularity of the length of the RT foreperiod

[[i.ei.e., interval between warning and go signals]., interval between warning and go signals]

Task and Situation Characteristics Task and Situation Characteristics Influencing Preparation, cont’dInfluencing Preparation, cont’d

6.6. Movement complexityMovement complexity•RT increases as amount of complexity of the action RT increases as amount of complexity of the action

increasesincreases First demonstrated by classic experiment by Henry and First demonstrated by classic experiment by Henry and

Rogers (1960) – Rogers (1960) – See A Closer LookSee A Closer Look

7.7. Movement accuracyMovement accuracy•RT increases as movement accuracy demands of the RT increases as movement accuracy demands of the

action increaseaction increase First demonstrated by evaluating RT results for Fitts’ tapping First demonstrated by evaluating RT results for Fitts’ tapping

tasks with different Indexes of Difficulty (tasks with different Indexes of Difficulty (i.ei.e. as MT increased, . as MT increased, RT also increased)RT also increased)

Task and Situation Characteristics Task and Situation Characteristics Influencing Preparation, cont’dInfluencing Preparation, cont’d

8.8. Repetition of a movementRepetition of a movement

9.9. Time between different responses to different Time between different responses to different signalssignals–Delay of response to 2Delay of response to 2ndnd stimulus (signal)is called stimulus (signal)is called

the psychological refractory period (PRP) – the psychological refractory period (PRP) – [[See Figure See Figure 8.38.3]]

–Relate to a situation in sports involving a “fake” Relate to a situation in sports involving a “fake” movement followed by the intended movement as the 2 movement followed by the intended movement as the 2 stimuli and the other player’s responses as the 2 stimuli and the other player’s responses as the 2 responsesresponses

Two Performer Characteristics Two Performer Characteristics Influencing PreparationInfluencing Preparation

Alertness of the performerAlertness of the performer–Warning signal effectWarning signal effect–Foreperiod length effect Foreperiod length effect [[See Fig. 8.4See Fig. 8.4]]–Vigilance effectsVigilance effects

Attention focused on the signal vs. the Attention focused on the signal vs. the movementmovement

–RT benefits more from focusing on the RT benefits more from focusing on the signal (e.g. signal (e.g. sprint start in swimming)sprint start in swimming)

Motor Control Events That OccurMotor Control Events That OccurDuring PreparationDuring Preparation

Postural preparationPostural preparation–Organization of movements needed for Organization of movements needed for

postural supportpostural supportAnticipatory characteristic of movement activity Anticipatory characteristic of movement activity

involved in postural preparationinvolved in postural preparation

Flexible synergistic organization characteristic of Flexible synergistic organization characteristic of postural movement preparationpostural movement preparation

Motor Control Events That OccurMotor Control Events That OccurDuring Preparation, cont’dDuring Preparation, cont’d

Limb performance Limb performance characteristicscharacteristics

e.ge.g. . MovementMovement

–DirectionDirection–TrajectoryTrajectory–End-point accuracy End-point accuracy

(i.e. for a ballistic (i.e. for a ballistic movement)movement)

Object control Object control characteristicscharacteristics

–Force controlForce control–End-state comfort End-state comfort

position (i.e. hand’s final position (i.e. hand’s final spatial position as initial spatial position as initial position)position)

Motor Control Events That OccurMotor Control Events That OccurDuring Preparation, cont’dDuring Preparation, cont’d

Sequences of Sequences of movementsmovements

–See research on See research on piano playing as piano playing as evidenceevidence

Spatial codingSpatial coding–Evidence from S-R Evidence from S-R

compatibility researchcompatibility research

Rhythmicity preparationRhythmicity preparation–Preperformance rituals Preperformance rituals

See examples in Table See examples in Table 8.18.1

Research shows they Research shows they appear to prepare relative appear to prepare relative timing of upcoming timing of upcoming movementsmovements