S-R Alternative

RT = a + b * Log2(N)

RT = reaction time a = y-intercept (simple RT) (best fit across the y-axis) b = slope (rate which RT increases) Log2 = "bits" of information N = number of stimulus response alternatives

Hick-Hyman Law

RT increases proportionally every time the number of alternative is doubled - increase in RT is related to the amount of information RT = a + b * Log2(N)

Feedback Control

Sensory feedback --> Motor Command --> Sensorimotor System --> Motor Output

Manipulating Target Width (W)

Smaller W increases mvmnt difficulty, thus mvmnt time increases

Fitt's Task

- Subject tap back & forth (reciprocally) between two targets - Movement Amplitude (A) and Target Width (W) manipulated - Number of taps in 20 seconds recorded - Average movement time = # of taps / 20 seconds

Effects of Response Complexity on RT

- complexity - defined as number of mvmnt components - manipulate complexity level - observe effects on RT

Effects of Response Complexity on RT for Henry & Rogers

- increase in mvmnt complexity lead to increase in RT - longer RT is related to extra time required to organize the response

Efferent Copy

An internal copy created with a motor command of its predicted movement and its resulting sensations

Feedforward Control

CNS PREDICTS the sensory consequences of the action Sensory feedback --> Motor Command --> Efferent copy (up arrow) and Sensorimotor System (horizontal arrow) --> Predictor --> Predicted Sensory Consequence meets with Discrepancy

The Fitts Tapping Task (Fitt's Law)

Examined the speed/accuracy trade-off in simple aiming mvmnts - Fitt's Law

Movement Complexity & Preparation

How does the complexity of the mvmnt influence the time for preparation?

How long does sensory feedback take to influence the movement?... in other words, is accuracy affected as speed increases with visual feedback and w/o visual feedback?

If you speed up mvmnt, there is less time for sensory feedback control so accuracy should not be affected by presence or absence of visual feedback

Manipulating Mvmnt Amplitude (A)

Larger A increases mvmnt difficulty, thus mvmnt time increases

Henry & Rogers study (1960) --> Task

Stimulus & response alternative for the mvmnt were held constant Task: 1. Lift finger from key following stimulus 2. Lift finger from key and move 33 cm to grasp a tennis ball 3. Lift finger from key and move 33 cm to grasp a tennis ball then move in the opposite direction to grasp a second tennis ball

Woodworth's two-phased reaching mvmnt:

1. Initial adjustment - propel the limb twd the target (planning phase) 2. Current-control - 'homing-in' on the target

In Fitts Equation, the slope is dependant upon:

1. Practice: slope decreases as a function of skill level (more practice = decreased slope) 2. Effector: slope dependent on the 'body part' 3. Age: slope increases as a function of age

Feedback Theory (Crossman & Goodeve)

- Rapid alterations b/t open & closed-loop processing Open-Loop: initiation of mvmnt twd the target (no sensory feedback) Closed-Loop: feedback phase (e.g. vision) correcting errors in the initial mvmnt trajectory --> this helps with accuracy

How long does it take for visual feedback to influence ongoing movement? ..... in other words, does duration of the mvmnt affect accuracy with lights on/off?

- Short mvmnts, accuracy is equivalent regardless of lights are on or off - Longer mvmnts, accuracy gets better when lights are on compared to off

Response Planning

- organize motor system for mvmnt - prepare "motor plan" - set of muscle commands

S-R Alternatives

As a number of S-R alternatives increases, RT increases

Speedy/Accuracy Demands

As mvmnt accuracy increases, the mvmnt time increases

Manipulating Target W & Mvmnt A

Larger A w/ larger W have similar mvmnt difficulty demands to smaller A & smaller W

Fitts Equation

MT = a + b (log2(2A/W)) Equation can be used to predict MT a = represents movement time when ID = 0 (two targets touching eachother) b = slope, represents the change in MT associate with a one unit change in ID log2(2A/W) = Index of Difficulty (ID) - an increase in ID leads to an increase in MT - ID relates to the processing demands of a task

Fitt's Results

MT increased linearly as W decreased or A increased - MT is approximately constant when the ratio of two times A (2A) to target width (W) is constant Equation: 2A/W Long mvmnts to large targets require the same MT as very short mvmnts to narrow targets

Feedback control

Mechanism for gathering information about performance deficiencies after they occur

Feedforward control

Monitor performance inputs that prevent or minimize performance deficiencies before they occur.