chapter 6 principles of speed, accuracy, and coordination
DESCRIPTION
Chapter 6 Principles of Speed, Accuracy, and Coordination. C H A P T E R. 6. Principles of Speed, Accuracy, and Coordination. Objectives. This chapter will help you to understand the following: Speed–accuracy trade-off in simple aiming movements - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/1.jpg)
Chapter 6 Principles of Speed, Accuracy, and Coordination
6
Principles of Speed, Principles of Speed, Accuracy, and Accuracy, and CoordinationCoordination
C H A P T E R
![Page 2: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/2.jpg)
Objectives
• This chapter will help you to understand the following:
– Speed–accuracy trade-off in simple aiming movements
– Logarithmic and linear relationships between speed and accuracy
– Relationship between timing accuracy and movement time
– Principles of bimanual timing and role of self-organizing principles
![Page 3: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/3.jpg)
Figure 6.1
![Page 4: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/4.jpg)
Fitts’ Law
• Fitts’ Law states that MT is constant whenever the ratio of the movement amplitude (A) to target width (W) remains constant.
• In addition, Fitts found that the MT increased as the ratio of A to W increased by either making A larger, making W smaller, or both.
(continued)
![Page 5: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/5.jpg)
Fitts’ Law (Continued)
• MT = a + b [Log2(2A/W)]
• where a and b are constants (the y-intercept and slope, respectively) and A and W are defined as before.
• The term Log2(2A/W) is referred to as the index of difficulty (ID).
• Fitts' Law says that MT is linearly related to the index of difficulty.
![Page 6: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/6.jpg)
Figure 6.2
![Page 7: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/7.jpg)
Linear Speed–Accuracy Trade-Off
• The linear speed–accuracy trade-off suggests that for various combinations of movement amplitude and MT that have a constant ratio (a constant average velocity), the aiming errors are about the same.
• Increases in movement distance and decreases in MT can be traded off with each other to maintain movement accuracy in rapid tasks.
![Page 8: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/8.jpg)
Figure 6.4
![Page 9: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/9.jpg)
Figure 6.5
![Page 10: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/10.jpg)
Sources of Error in Rapid Movements
• In summary, this is why increasing the speed of a rapid movement contributes to its inaccuracy:
– The relative contraction forces of the various participating muscles are a major factor in determining the ultimate trajectory of the limb.
– The inconsistency in these forces increases with increased force.
(continued)
![Page 11: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/11.jpg)
Sources of Error in Rapid Movements (continued)
– When MT decreases, more force is required.
– When amplitude increases, more force is required.
– More force generates more variability, which causes the movement to deviate from the intended trajectory, resulting in errors.
![Page 12: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/12.jpg)
Figure 6.7
![Page 13: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/13.jpg)
Very Forceful Movements
• Here's what results when a movement requires very high levels of muscular contractions (greater than about 70% of the subject's capabilities):
– Increasing speed by reducing MT can decrease spatial and timing error.
– Because a greater muscular force requirement increases accuracy, adding inertial load to the movement can decrease error, up to a point.
(continued)
![Page 14: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/14.jpg)
Very Forceful Movements (continued)
– An inverted-U relationship exists between spatial accuracy and force requirements, with least accuracy at moderate levels of force.
![Page 15: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/15.jpg)
Movement Timing
• Skills with purely temporal goals seem to follow somewhat different principles than those having purely spatial goals.
• Decreasing the MT has the effect of decreasing the timing error for skills with temporal goals, making the movement more accurate in time, not less.
![Page 16: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/16.jpg)
Figure 6.9
![Page 17: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/17.jpg)
Bimanual Aiming Tasks
• Bimanual Fitts’ task
• Both limbs could be assigned identical tasks with either low or high IDs, or the limbs could also be assigned to different (incongruent) tasks
• The explanatory power of Fitts’ Law is reduced when separate and incongruent task demands are required of two limbs
(continued)
![Page 18: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/18.jpg)
Bimanual Aiming Tasks (continued)
• This finding could be a result of an attempt by the executive to deal with an overloaded attentional demand by issuing a single motor program that controls both limbs
• Conclusion is supported by other bimanual research, and these findings support a view on which the MT and kinematics for both limbs are not determined independently but rather by a joint command
![Page 19: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/19.jpg)
Continuous Bimanual Timing
• When controlling the continuous movement of two limbs, each with its own spatial or temporal goal (or both), because the movements are ongoing, the executive can do the following:
– Use a common movement command to control the movements of both limbs
– Switch attention rapidly between the executions of the two tasks
![Page 20: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/20.jpg)
Coordination as a Self-Organization Process
• The notion of the motor program is not without its critics.
• Investigators from the self-organization perspective hold that the regularities of movement patterns are not represented in programs but rather emerge naturally out of the complex interactions among many degrees of freedom.
![Page 21: Chapter 6 Principles of Speed, Accuracy, and Coordination](https://reader034.vdocuments.site/reader034/viewer/2022050700/568134aa550346895d9bb9eb/html5/thumbnails/21.jpg)
Speed–Accuracy Trade-Off Reconsidered
• The increased complexity of coordinating two movements also provides more flexibility, such that increases in speed result in changes to the coordination pattern in order to maintain stability.