Human motor control
Introduction
Turing test: method of judging intelligence. It is a test for understanding
verbally expressed intelligence.
There are three different levels of analysis that characterize the study of
human motor control:
- Computational level: description, often expressed mathematically, of
one or more functions that a system is supposed to achieve.
- Procedural level: concerns events that occur in real time.
- Implementation level: physical stuff that permits procedures to be
physically achieved.
Physics helps determine the factors that limit performance and can indicate the
factors that enable performance.
Engineers work on issues related to motor control such as robotics/prostheses.
The control theory is an approach to the analysis of feedback.
The study of variability as well as other features of data is the focus of statistics.
Behavioural scientist study overt physical activity to predict and control
behaviour. Cognitive scientist are interested in the procedural level, but
especially in the internal processes that allow behaviour to unfold, the software.
Human factors specialists are interested in the applications of behavioural and
cognitive science to practical problems.
Core problems
Ways to organize the body of knowledge comprising the field of human motor
control:
- Discipline: taking what has been learned in the various approaches to the
fields
- Method: considering the techniques used to analyse the human motor
control system
- Activity: focusing on things people
- Core problems: degrees of freedom, sequencing and timing, perceptual-
motor integration and learning problem.
Degrees of freedom problem: most physical tasks can be performed in an
infinite number of ways. It gives you the option of performing the task in a way
that makes sense at the moment, it is an opportunity to adapt to changing
environmental conditions. The problem is: how are particular actions chosen
when many are possible. It applies for instance to kinematics (positions in time)
and kinetics (forces in time). There are different ways to address the problem:
- Synergies: interactions, they can reduce the number of degrees of
freedom that must be independently controlled. It is a so-called soft
constraint, it can help reduce the problem to be independently managed
but is not absolutely mandatory.
- Physical mechanics: physical properties of the body can eliminate the
need to control each feature of neuro-motor control.
- Efficiency: movements we make are usually more efficient than the
movements we don’t make. Ending in a comfortable way is an efficiency
constraint. Another is the tendency to move smoothly when going from
one position to another (minimize the mean squared rate of change of
acceleration over movement time).
, Sequencing and timing problem: how do we control the sequencing and
timing of our behaviours? The elements of the behaviours must be ordered
correctly in time.
An example of a spoonerism are speech errors involving the exchange of two
speech sounds in analogous word positions. Consonants only exchange with
other consonants, this is the same for vowels, nouns and verbs.
Action slip: the specifics of the task situation are momentarily misidentified.
Anticipatory lip rounding illustrates a general tendency that any theory of
sequencing must account for, namely the tendency of effectors to coarticulate
(simultaneous motions that occur in sequential tasks). It is an effective mean for
increasing response speed.
Generation movements in the right order is important, but generating
movements with the right timing can be even more so.
Perceptual-motor integration problem: how are perception and motor control
combined? Virtually all aiming proceed in two stages: a rapid ballistic phase
(movements cannot be altered once they are initiated, they are typically fast and
cover most of the distance to the target, when the target isn’t reached feedback
is used to correct the error) and a slower corrective phase. Corrective errors
based on feedback is possible with a negative feedback loop (a
servomechanism), which has several components. One is a reference signal,
which provides input to the loop about the target, another is the plant, which is
responsible for converting control signals into output and the last is the
comparator, which measures the discrepancy between the sensed position of
the effector and the reference signal. The comparator is used to negate error.
Positive feedback loop: a loop in which feedback leads to larger errors, not
smaller ones.
Closed-loop control: occurs when feedback returns to the comparator.
Open-loop control: occurs when feedback is unavailable. The feedback loop is
opened up and no information can get through about the success or failure of
performance.
When you hit the target based on prediction you use feedforward control. Gross
features of some movements can be performed under feedforward control, when
these are performed with feedback, they are usually performed more precisely
and gracefully. It helps distinguishing perceptual changes due to motion arising in
the external environment form perceptual changes arising from one’s own
motion. Everyday movements reflect the combined use of feedforward and
feedback.
Saccadic suppression could help reduce the damage to visual perception
caused by retinal smearing.
Reafference: the perceptual consequence of one’s own action.
Exafference: perceptual input arising from outside influences.
Perception (or at least visual) is embodied (the way the environment is
perceived is mediated by what we see we can do in the environment).
Functional magnetic resonance imagery (fMRI) makes it possible to determine
which parts of the brain become active when different tasks are performed.
Mirror neurons fire both when people perform actions and when they see
others perform the same actions.
Learning problem or the skill acquisition problem:
- Learning by doing: the only way to learn what perceptual changes
accompany the movements we make is to explore them via active
exploration. You form correlations between movements and perceptions.
Introduction
Turing test: method of judging intelligence. It is a test for understanding
verbally expressed intelligence.
There are three different levels of analysis that characterize the study of
human motor control:
- Computational level: description, often expressed mathematically, of
one or more functions that a system is supposed to achieve.
- Procedural level: concerns events that occur in real time.
- Implementation level: physical stuff that permits procedures to be
physically achieved.
Physics helps determine the factors that limit performance and can indicate the
factors that enable performance.
Engineers work on issues related to motor control such as robotics/prostheses.
The control theory is an approach to the analysis of feedback.
The study of variability as well as other features of data is the focus of statistics.
Behavioural scientist study overt physical activity to predict and control
behaviour. Cognitive scientist are interested in the procedural level, but
especially in the internal processes that allow behaviour to unfold, the software.
Human factors specialists are interested in the applications of behavioural and
cognitive science to practical problems.
Core problems
Ways to organize the body of knowledge comprising the field of human motor
control:
- Discipline: taking what has been learned in the various approaches to the
fields
- Method: considering the techniques used to analyse the human motor
control system
- Activity: focusing on things people
- Core problems: degrees of freedom, sequencing and timing, perceptual-
motor integration and learning problem.
Degrees of freedom problem: most physical tasks can be performed in an
infinite number of ways. It gives you the option of performing the task in a way
that makes sense at the moment, it is an opportunity to adapt to changing
environmental conditions. The problem is: how are particular actions chosen
when many are possible. It applies for instance to kinematics (positions in time)
and kinetics (forces in time). There are different ways to address the problem:
- Synergies: interactions, they can reduce the number of degrees of
freedom that must be independently controlled. It is a so-called soft
constraint, it can help reduce the problem to be independently managed
but is not absolutely mandatory.
- Physical mechanics: physical properties of the body can eliminate the
need to control each feature of neuro-motor control.
- Efficiency: movements we make are usually more efficient than the
movements we don’t make. Ending in a comfortable way is an efficiency
constraint. Another is the tendency to move smoothly when going from
one position to another (minimize the mean squared rate of change of
acceleration over movement time).
, Sequencing and timing problem: how do we control the sequencing and
timing of our behaviours? The elements of the behaviours must be ordered
correctly in time.
An example of a spoonerism are speech errors involving the exchange of two
speech sounds in analogous word positions. Consonants only exchange with
other consonants, this is the same for vowels, nouns and verbs.
Action slip: the specifics of the task situation are momentarily misidentified.
Anticipatory lip rounding illustrates a general tendency that any theory of
sequencing must account for, namely the tendency of effectors to coarticulate
(simultaneous motions that occur in sequential tasks). It is an effective mean for
increasing response speed.
Generation movements in the right order is important, but generating
movements with the right timing can be even more so.
Perceptual-motor integration problem: how are perception and motor control
combined? Virtually all aiming proceed in two stages: a rapid ballistic phase
(movements cannot be altered once they are initiated, they are typically fast and
cover most of the distance to the target, when the target isn’t reached feedback
is used to correct the error) and a slower corrective phase. Corrective errors
based on feedback is possible with a negative feedback loop (a
servomechanism), which has several components. One is a reference signal,
which provides input to the loop about the target, another is the plant, which is
responsible for converting control signals into output and the last is the
comparator, which measures the discrepancy between the sensed position of
the effector and the reference signal. The comparator is used to negate error.
Positive feedback loop: a loop in which feedback leads to larger errors, not
smaller ones.
Closed-loop control: occurs when feedback returns to the comparator.
Open-loop control: occurs when feedback is unavailable. The feedback loop is
opened up and no information can get through about the success or failure of
performance.
When you hit the target based on prediction you use feedforward control. Gross
features of some movements can be performed under feedforward control, when
these are performed with feedback, they are usually performed more precisely
and gracefully. It helps distinguishing perceptual changes due to motion arising in
the external environment form perceptual changes arising from one’s own
motion. Everyday movements reflect the combined use of feedforward and
feedback.
Saccadic suppression could help reduce the damage to visual perception
caused by retinal smearing.
Reafference: the perceptual consequence of one’s own action.
Exafference: perceptual input arising from outside influences.
Perception (or at least visual) is embodied (the way the environment is
perceived is mediated by what we see we can do in the environment).
Functional magnetic resonance imagery (fMRI) makes it possible to determine
which parts of the brain become active when different tasks are performed.
Mirror neurons fire both when people perform actions and when they see
others perform the same actions.
Learning problem or the skill acquisition problem:
- Learning by doing: the only way to learn what perceptual changes
accompany the movements we make is to explore them via active
exploration. You form correlations between movements and perceptions.
