kin251 exam 2

What are the key characteristics of skilled performance?

• Achieves goals with high accuracy (certainty)

• Uses minimal energy (mental + physical)

• Uses minimal time

• Involves: perception, decision-making, motor control

How do open and closed skills differ?

• Open skills: performed in changing, unpredictable environments (e.g., soccer)

• Closed skills: performed in stable, predictable environments (e.g., archery)

What distinguishes discrete, serial, and continuous skills?

• Discrete: clear start and end (e.g., dart throw)

• Serial: sequence of discrete actions (e.g., gymnastics routine)

• Continuous: ongoing, no clear start/end (e.g., swimming)

What do CE (Constant Error), AE (Absolute Error), VE (Variable Error), and RMSE (Root Mean Square Error) measure in motor performance? What contexts are they used?

• CE: directional bias (over/under target)

• AE: overall accuracy (magnitude of error)

• VE: consistency (spread of performance)

• RMSE: combined error (bias + variability), used in continuous tasks like tracking

Can you estimate CE, AE, VE if provided a distribution of points from an experiment?

• Yes:

  • CE = average signed error

  • AE = average absolute distance from target

  • VE = variability around the mean error

What are the stages in the information processing model for human performance?

1. Stimulus identification

2. Response selection

3. Movement programming

What is the difference between reaction time (RT), movement time (MT), and response time?

• RT: stimulus → start of movement

• MT: movement execution

• Response time: RT + MT

How does each processing stage influence overall reaction time?

• Slower stimulus recognition → longer RT

• More choices → longer RT

• More complex movement → longer RT

What does Hick’s Law tell us about reaction time and decision-making? What is the shape of the curve in Hick’s law?

• More choices → longer reaction time

• Relationship is logarithmic (curved, not linear)

How does stimulus-response compatibility affect reaction time? How can we deal with S-R incompatibility?

• High compatibility → faster RT

• Low compatibility → slower RT

• Practice improves S-R compatibility

How can anticipation reduce reaction time?

• Allows movement to begin early or immediately

• Can reduce RT close to 0 ms

• Risk: incorrect anticipation worsens performance

What is the speed-accuracy tradeoff, and how is it explained by Fitts’ Law?

• Faster movement → less accurate

• Higher accuracy → slower movement

• Fitts’ Law: MT = a + b * log₂(2A/W)

  • MT increases with: larger distance (A) or smaller target (W)

What are the “independent” and “dependent” variables involved in Fitts’ law? What do the slope and intercept represent?

• Independent variables: A (distance), W (target size)

• Dependent variable: MT

• Intercept (a): baseline speed

• Slope (b): information processing capacity

Why does increasing speed typically reduce accuracy in spatial tasks?

• More force variability (signal-dependent noise)

• Less time for corrections

How is Fitts’ Law applied in computer interface design?

Make buttons larger and closer → faster user interaction

What is the speed-accuracy relation in temporal (or timing) tasks?

Opposite pattern: faster movement → better timing accuracy

Why are tasks like hitting a baseball that involve both spatial and temporal constraints challenging? How do athletes deal with such constraints?

• Require: high spatial accuracy (slow) + high temporal accuracy (fast) → conflicting demands

• Athletes: keep movement timing consistent (downswing) and adjust setup timing (backswing/start)

What are the defining characteristics of closed-loop control?

• Uses feedback during movement

• Allows real-time corrections

• Best for slower movements

What components make up a closed-loop control system?

1. Executive

2. Effector

3. Comparator (reference)

4. Error signal

What types of sensory feedback do humans use in movement control?

Vision, Audition, Touch, Proprioception, Vestibular

What are the two visual streams, and how do they contribute to movement?

• Ventral: “what” → object identification

• Dorsal: “where/how” → movement control

What is optic flow?

Visual info about motion (expansion = approaching, contraction = moving away)

How does proprioception contribute to reflexive control?

• Provides body position info

• Enables fast reflex corrections (30–80 ms)

What are the advantages and disadvantages of closed-loop control?

• Advantages: flexible, adaptive

• Disadvantages: slow, feedback delays

What are the characteristics of open-loop control?

• Pre-programmed movement

• No feedback during execution

• Used for fast actions

What are the pros and cons of using open-loop control?

• Pros: fast, efficient

• Cons: cannot adjust mid-movement

What is a motor program, and what evidence supports its existence?

• Pre-structured movement plan

• Evidence:

  • RT increases with complexity

  • Startle responses trigger prepared movement

  • Movement possible without feedback

How does learning occur in open-loop control systems?

Feedback after movement → corrections for next trial

What is a Generalized Motor Program (GMP), and what evidence supports it?

• Template for movement

• Can adjust speed, force, limbs

• Solves storage + novelty problems

How can predictions act as a form of fast feedback?

Brain predicts outcomes before feedback arrives → acts like immediate correction

How can open- and closed-loop control systems be combined?

• Open-loop: fast execution

• Closed-loop: corrections

• Both used together

What does “degrees of freedom” mean in movement control?

Number of ways a body can move

What is the “degrees of freedom problem”?

Too many movement possibilities to control individually

What is context-conditioned variability, and how do anatomical, mechanical, and physiological factors contribute?

Movement changes depending on anatomical, mechanical, physiological factors

What are strategies to simplify the degrees of freedom problem?

• Freeze degrees of freedom

• Create synergies (link movements)

How do motor plans, motor commands, and feedback contribute to postural, locomotor, and hand-eye coordination?

• Motor plan: sets goal

• Motor command: executes movement

• Feedback: monitors and corrects

How does the dynamical systems view of coordination differ from the motor program view?

• Motor program → top-down control

• Dynamical systems → self-organizing patterns

What did Kelso’s “finger wiggling” experiment reveal about motor control?

• In-phase = most stable

• Anti-phase unstable at high speeds

What rules seem to underlie temporal coordination in bimanual tasks?

• Same muscles easier

• 1:1 rhythms easiest

• Simple ratios easier than complex

What rules seem to underlie spatial coordination in bimanual tasks?

• Same direction easier

• Different amplitudes interfere (assimilation)

How does Fitts’ Law apply to bimanual movements? How is it different from the unimanual case?

• Both hands act as one system

• Harder task slows both hands

How can task conceptualization help overcome temporal and spatial constraints?

• Turns task into single unified action

• Reduces planning difficulty

What are the differences between learning “part” versus “whole” in bimanual coordination?

• Whole practice (both hands together) better

• Part practice less effective