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CopyofKine4100Group4.pptxCH:4 Theoretical Perspective
By: Precious Salazar, Fabian Zamora, and Jaslie Gomez Martinez
Questions to focus on
What is a scientific theory, and why are theories important in the study of motor skills?
What are the relative strengths and weaknesses of each of the major
theories underlying the study of motor skills?
How can differing theories be useful in explaining motor skill behavior, even when they are based on seemingly contradictory theoretical assumptions?
Theory
Theory: a coherent statement or set of statements relating a large number of observations into a logical and testable framework; a theory must be open to empirical verification and prediction of future observations within its conceptual area of phenomena
Provides a perspective, allows us to see how individual facts are connected to form a single, meaningful picture of human movement
How to know if its a good theory?
it accounts for a significantly large class of observations on the basis of only a few simple, though powerful, propositions. Second, it makes definite predictions about the results of future observations—it is testable.
Two major theories
Closed control system: A system in which the mechanisms of control are internal and closed to influences outside of the system itself.( Focuses on the working of the central nervous system)
Open control system: A system that interacts with the environment outside of itself and responds to external influences in its mechanisms of control.
More than one theory can be correct
cognitive-based and dynamical systems perspectives both meet criteria to be good scientific theories
both explain in fairly parsimonious yet elegant terms a large and diverse set of observations concerning human movement.
Both also have proved successful in predicting new observations,
Cognitive Based theory
The oldest and probably most intuitive approach to understanding how movement skills are acquired and controlled is to consider them as products of mental activity, or in more psychological terms as products of cognitive processes.
motor program: A procedural memory comprised of the rules commanding muscular activity for producing specific skills.
The idea of a motor program, taking a good deal of license with the concept, is so immediately intuitive that it goes back at least 25 centuries, to the time of the ancient Greeks and the philosopher Plato. Plato believed that before a movement could be performed, a person first had to form an idea, a mental picture, of the movement.
Information Processing Model
information processing model: A model of cognitive processes occurring in the central nervous system underlying the production of motor skills; three stages are identified, including the perceptual,decision-making, and programming stages.
perceptual stage:The first stage of information processing in which sensory information is detected and identified.
Decision Making Stage: the individual uses information transmitted from the perceptual stage to decide upon a course of action. In this stage, information from the perceptual stage is compared to past information to determine an appropriate action
Programming Stage: preparing the appropriate motor program to carry out the action decided upon in the decision-making stage.
Closed-Loop Systems
This is also referred to as a Servo-Mechanism. This is an error detection device that constantly monitors the system for discrepancies between desired and actual conditions and automatically makes adjustments to correct detected errors. In a closed loop control corrections are made on the basis of feedback.
Closed-loop systems are believed to underlie the control of movements that are relatively slow and deliberate. (ex. Driving a car, threading a needle, running to catch a fly ball, maintaining one’s balance while standing still)
Closed-Loop system (cont.)
Closed-loop control does not depend upon detailed movement instructions.It depends on a more general set of controlling guidelines, coupled with task- specific goals, initiate action, and feedback is then used to adjust muscular commands in compliance with task goals.
Closed-loop control is a hierarchical system with one important distinction. control centers responsible for initiating, monitoring, correcting, and commanding lower levels of the musculature entail central processes within the brain, information necessary to these central processes is derived through sensory feedback.
Advantages & Disadvantages of Closed-Loop Control
Advantages
especially appropriate when performing unpracticed skills
obvious advantage of allowing movements to be corrected once they have begun, rather than having movement errors continue until action is completed
constant error detection and correction processes, can result in precise and accurate movement
Disadvantages
they are attention demanding so, because of the requirement to monitor feedback and generate new movement commands in response, individuals must use much of their conscious and attentional resources in maintaining the quality of their movements.
time required to prepare and execute successive corrections to an ongoing action. This means too little time to allow for the preparation of corrective actions
Open-Loop Systems
There is no mechanism for monitoring sensory feedback and correcting ongoing movements, as in a closed-loop system. Perceptual sensing mechanisms detect information in the environment and act to determine whether a response is required.
FeedForward: Rather than using sensory information as feedback during the performance of a skill, open-loop systems use environmental information in order to prepare the motor system
Open-loop control appears to underlie many skills that individuals perform everyday. Skills that are performed quickly (with insufficient time available for attending to feedback) and automatically (with little or no conscious attention paid to them) are excellent candidates for open-loop control
Advantages and Disadvantages for Open-Loop System
Advantages
It is capable of producing quick movements because the commands for action are prestructured and, once initiated, carried out without the need for further major modification.
Because movement commands are prestructured, attentional resources can be directed toward other tasks rather than being diverted to the conscious control of ongoing movement.
Disadvantages
it is not effective for skills which are unpracticed or not well learned. The motor programs for such skills would be either insufficiently developed or absent altogether. It should be remembered that motor programs are a type of memory, and until such memories are sufficiently developed through repetition and practice, sufficient motor commands for effective skill production are unavailable
because motor programs anticipate particular environmental conditions, open-loop control is not effective in changing environments.
Open-/Closed-Loop Control Continuum
Closed-loop theory proposed by Jack Adams at the University of Illinois.
A major difference in these two theories was the role accorded sensory feedback in the production of motor skills.
Those favoring closed-loop models tended to conduct research investigations utilizing relative slow, self-paced skills such as tracking tasks to demonstrate the explanatory efficacy of closed-loop models.
Open-loop theory proposed by Richard Schmidt at the University of Southern California.
Supporters of open-loop systems, on the other hand, typically designed their investigations around rapid, discrete tasks, which generally favored open-loop explanations of control.
These two types of control can be viewed as describing different ways in which the central and peripheral nervous systems initiate and control actions.
Open-/Closed Loop Continuum
An example of the symbiotic cooperation between closed-loop and open-loop control processes is observed when considering how individuals balance between speed and accuracy when performing rapid tasks.
Examples: Pitching fastball, parry in fencing, speed typing
Fast and accurate to be successful. However if done too fast you will have more errors and do poorly
Speed–accuracy trade-off: The observation that in the performance of many skills an increase in the speed with which the skill is performed is accompanied by a decrease in performance accuracy, and vice versa.
Fitts Law
The trade-off between speed and accuracy is described by Fitts’ law, one of the oldest and most important laws of motor control.
Fitts’ law: Law expressing the mathematical relationship between speed of movement and accuracy for discrete aiming tasks.
Although its original application was to continuous aiming tasks, the predictions of Fitts’ law have been shown to hold for discrete as well as continuous skills, for individuals of all ages, for skills using different effectors (fingers, hands, arms, legs), and for skills performed underwater as well as on land.
Fitts Law
Attempts to reconcile the implications of Fitts’ law with the notions of open and closed-loop control mechanisms eventually led to the conclusion that both control systems play essential roles when both speed and accuracy are important in achieving task goals.
Three phases of control have been proposed.
1st phase (movement preparations): individual evaluates the environmental conditions present, determines that the appropriate action requires a rapid response, selects the appropriate motor program from memory, and programs the needed motor commands.
2nd phase (initial flight/ first movement phase): phase, the preprogrammed motor program is initiated through open-loop control, purpose of this phase is to move the requisite body part toward a target or final location quickly.
3rd phase (termination phase/ happens at end of the movement): under closed-loop control, the individual uses feedback (primarily visual) to assess the accuracy of the initial flight phase and makes any needed final corrections necessary for completing the task successfully.
Adams closed loop theory
He believed that learning involved the forming and strengthening of neural traces in the brain’s cortex.
His conception, a motor program consisting of two separate traces was responsible for the learning and control of all voluntary motor skills.
If sensory feedback from the ongoing action does not match the perceptual trace, then new muscular commands are generated to bring sensory feedback into alignment with desired action goals.
Adam’s closed loop theory cont.
Memory trace: role of the memory trace, according to Adams’ theory, is to select and initiate the desired action. Once initiated, the primary responsibility for the ongoing control of a movement is assigned to a second cortical trace called the perceptual trace.
Perceptual trace: evaluates the correctness of the action executed by the memory trace. It continually monitors and compares response-produced feedback from ongoing movement with a reference of correctness representing the feedback qualities expected in a correct response.
The theoretical implications of Adams’ closed-loop model supported several conclusions concerning the practice of skills, placing especially considerable emphasis on the roles of practice repetitions and augmented feedback.
Problems of novelty and storage
Problems of novelty and storage came to be by the one’s involved in the study of motor skills
Novelty Problem: was one of the first problems, it is a deficiency of simple motor program theory based on the notion that individuals should be unable to effectively produce unpracticed variations of learned movements because they have not developed specific motor programs for them.
Since a memory trace is a result of practice, an unpracticed skill cannot be performed correctly for the first time
So, Adam’s theory, the memory trace is nonexistent because it has not been developed through previous practice
Novelty Problem Storage Problem
This problem can be immediately recognized in everyday situations.
Ex: people will have many years of driving experience but suddenly they come across a new situation or road conditions that they have never experienced but they can still easily adapt their driving.
Slight differences in how a skill was practiced would require a separate and specific memory or motor program
It’s hard to explain how the vast number of individual memory structures are needed because there are so many skills and different types of skill that people are able to perform
Schmidt’s Schema Theory
A theory of motor programs first proposed by Schmidt in 1975 that assumes that motor programs are made up of an abstract set of rules that can be generalized to control an entire class of actions.
Schmidt recognized that there was a problem with contemporary theories, such as that proposed by Adams, thus the problems of novelty and storage.
Schmidt’s solution: every unique expression of a skill does not require a separate motor program, but that the motor program is more general in nature and adaptable to a wide variety of different ways in which a specific skill might be performed
provided a new and useful framework for studying motor skills
It advanced our understanding of how skills are learned and controlled
Invariant feature of the GMP (generalized motor program)
Ex: Writing a certain phrase in different ways may change the features of your writing
those features that did not change from one writing method to another are called invariant features
There are 3 sources of invariance in human motor skills:
the sequencing of actions or components: writing the phrase in the same order
relative timing: the proportion of time used each time to write a letter was always constant
relative force: the force used for each phrase was also constant in each scenario
GMPs form rules for a “movement class.”
Schmidt termed all the different ways a skill might be performed while relying on the same rules of sequence, relative timing, and relative force, as a movement class.
All of the possible movements controlled by a single generalized motor program, typically sharing common coordination patterns.
Ex: Throwing softballs at various distances can be considered as a movement class
This is because regardless of the distance thrown, even to an unpracticed distance, the throwing action is still accomplished by the same rules and so can be effectively accomplished by the GMP.
Variant Features of the GMP
Variant feature: The aspects of a motor program that change from one performance attempt to another, including bodily states, environmental factors, and task goals.
Parameters: Features of a skill that must be added to the invariant features of a generalized motor program to meet the specific demands of a situation. They include overall duration, overall force, and muscle selection.
They can be easily modified from one performance to another to improve motor response variations
Example:
throwing the ball to the third base from different areas of the field
Walking up and down stairs from different heights
3 Parameters in Schema Theory
1. The overall duration: can be increased or decreased as a unit according to changes in the overall duration parameter
2. The overall force: the overall force and amplitude (size of the movement) can be modified.
3. The muscle selection: the various effectors that can be used to perform the same movement (hand, foot, mouth in writing) can be modified
All of these correspond to the 3 rules of invariance
Specifying Parameter Values—The Schema
Schema: A set of rules relating the various outcomes of an individual’s actions to the parameter values the individual chooses in order to produce those outcomes
Ex: short distance of throw would be the individuals actions
Produced outcomes would be the small amount of force
Schema theory is based on adapting to previous experiences.
Each movement attempt provides the learner with information about the movement that is translated into a relationship which will then be used to guide future attempts.
MODERN DYNAMICAL SYSTEMS THEORY
Dynamical systems are systems in motion,or systems that change over time.
Dynamical systems that act in nonlinear ways share an important characteristic that they are complex.
Ex: Neither a rock nor an airplane is a dynamical system, but the geological evolution of rocks and the flight of airplanes are dynamical.
Dynamical Systems and Complexity
To be complex a system must exhibit all four of these qualities:
Diversity (comprised of many elements differing in kind)
Connection (form a linked network)
Interdependence (a change in one element affects all other elements)
Adaptation (capable of change, i.e., of learning)
Systems that exhibit complexity, such as human movement, produce bottom-up, emergent phenomena. This is expressed by two essential and cooperating features of dynamical systems theory… Emergence and Self Organization
Complexity: A characteristic of systems that are comprised of diverse elements that are connected and interdependent, and capable of adaptation.
Examples of complex systems include areas as diverse as weather and climate,economics, biological systems, chemical reactions, bird migration patterns, population growth, highway traffic flow, social fads, and baseball records. Human movement skills also possess the qualities of complexity
Self Organization & Emergence
Emergence: entails the creation of something new that transcends the parts from which it is produced.
Ex: Consciousness does not reside in an individual neuron but when millions of neurons are organized consciousness emerges.
With emergence something new is created (the macro (consciousness) differs from the micro(neurons)
Self-organization: The tendency for elements within a complex system to synergistically adapt so that new states or patterns emerge.
No overall command structure
A process whereby the organization of a system spontaneously increases and becomes more stable because of inherent properties within the system itself.
Ex: the spontaneous formation of crystals, the homeostatic self-maintaining nature of cells, and the formation of galaxies
Self organization
Two Characteristics
Openness: the system is open to its environment, that it actively seeks information from its environment and makes that information widely available to all parts of the system.
Self-reference: deterministic principles inherent within the system itself that guide the organization of the system
When information is received by the system concerning changes in the external environment, the system always adapts in a way that remains consistent with its own inherent guiding principles.
The Emergence of Motor Skills—A Dynamical Systems Analysis
Three premises about the control and learning of all motor skills:
Various constraints impose boundaries on movement possibilities.
Diverse movement system components self-organize into emergent patterns.
Self-organization directs emergence toward preferred, attractor states.
State space: All of the possible patterns or states that a system is capable of assuming.
The state space for water includes all of the temperatures between 32° F and 212° F.
Movement constraints
Constraint: Boundaries that limit the possible values or patterns that a system can assume that are imposed by the organism, physical environment, and task itself
Ex: water is limited to temperatures between 32° F (ice) and 212° F(steam).Water is therefore constrained, or bounded, by temperature.Temperature is a constraint for water
organismic constraint: Characteristics of an individual that act as constraints on movement, including structural characteristics such as height, weight, and body shape, as well as functional characteristics such as intelligence,motivation, and psychological states.
Environmental constraint: Features of the physical environment such as gravity, temperature, and light that act to constrain movement patterns; also includes social features such as cultural norms that constrain movement behavior.
task constraint: Constraints on human movement imposed by the task performed, including task goals, equipment used, and mandated rules and procedures.
Combined effects of constraints
Each category of constraints and each individual constraint within those categories imposes its particular boundaries upon movement options.
the combined effects of all constraints acting upon the moving person are synergistic.
Awareness of the three ways in which movement is constrained and of the interactions among the task, person, and environment is also critical to effective practice and learning
Attractors of Phase Shifts
Phase shift: In a dynamical system, the spontaneous transition from one organizational pattern to another as a result of self-organization.
Ex: sudden breakup of a smooth flowing stream into a rushing turbulence, a kernel of corn popping
Attractor: an organizational arrangement that keeps a system’s component parts working in harmony to fulfill the system’s mission
A system may have a number of attractors, each one being more effective than the others under given environmental conditions.
Relative to human movement systems, attractors are states of spatial-temporal muscular organization that are able to maintain stable movement patterns with the greatest efficiency in specific situations
Keslo & Schoner Experiment
Subjects were told to move their index fingers in beat to the metronome.
Subjects fingers were doing the same movements simultaneously but opposite.This is called antiphase because two fingers are actually out of phase with one another doing opposite things.
The speed of the metronome gradually increased
This caused a new pattern called Inphase to arise. Inphase: both fingers adducted and abducted at the same time.
researchers observed that as the speed of the metronome increased, there was a point at which subjects maintained the antiphase pattern even though it was becoming more and more difficult for them to do so. It was only when a critical speed was finally reached that the new and more effective in-phase pattern spontaneously emerged.
