Principles of Speed, Accuracy and Timing - Chap. 6 Flashcards
what is the idea behind fitts law
movement time is constant whenever the ratio of the movement amplitude to target width remains constant (long movements to wide targets = short mvoemetns to narrow targets)
-MT increased as ratio of amplitude to width increased
what does fitts law predict
how much time you require to move to a target when speed and accuracy matter
what is the fitts law equation
MT = a + b [log2(2A/W)]
A = amplitude (distance between 2 targets)
W = target width
log2(2A/W) = index of difficulty
how does speed-accuracy trade-off relate to open and closed loop control
faster = open loop commands are more variable
what are 3 things that fitts law tells
-movement time increases as distance icnreases
-mt increases as target widht decreases
-mt is different for a given index of difficulty
what are 2 cases in which the speed-accuracy trade-off does not hold
-extremely rapid and forceful actions are involded
-accuracy in timing is the actions critical feature
how do extremely rapid and forcelful actions not hole to the speed-accuracy trade off
-increasing speed by reducing MT can decrease spatial and timing error
-greater msucualr force requirment actually increases accuracy in this range, adding an inertial load can decrease error (up to a point)
-
how is effective target width a violation of fitts law
how scattered are movement endpoints within a given target
-effective target width = actual target width
-BUT if only honing into one area on the target, for example the middle, fitts law wont hold because behaving as if target is narrow rather than bid so effective target does not equal actual target
what is schmidts law
describes relationship between movement force and mvoement variability
effective target width increases as what increases
velocity
moving faster results in what
a linear increase in an endpoint variability
what is a question regarding sources of error in rapid movements
where does the noise come from
when motor program is sent down spinal cord fast, there is more opportunity for what
noise/mistakes
-dont take time to take in feedback and compare to wanted outcome and modify actions
-gives less time to corrrect any possible mistakes
what are 3 exceptions to speed accuracy trade off
-extremely rapid and forceful movements
-visual illusions
-movement timing
when it comes to speed, what movements have hte most spatial accuracy and hte least
MOST
-very rapid and very slow
LEAST
-moderate-speed
**goes against the speed-accuracy trade off (faster moements are always less spatially accurate)
what is one way to help train someone to perform better
ex golf: practice putting into a hole that is percieved smaller than what it really is and this will transfer postitvely into the actual size hoel allowing to be more accurate
skills with purely temporal goals seem to follow somewhat different principles than what
those having purely spatial goals
why does a task that takes longer produce more errors than one thats shorter
becuase hte longer durations allow for more noise/variability and they acculumate as the duration of the even to be timed increases
in what context is movement time not accurate to the speed accuracy trade off
when tasks are timed
-the longer the duration of the task, the more possibility for errors
when performing a rapid movement what is critical
timing
when to initiate a rapid movement is based on knowing the what
the duration of the movement
what is a coincidence anticipation task
predict the arrival of a moving object at a point in space
-swinging at a baseball
what is the process of executing a rapid movement
decision making (stimulus identification)
implementing decision (reponse programming)
executing movements (movement time/actually performing respponse)
from a visual processing standpoint why do basbelal players swing near maximmum
shortening MT, delyas the beinning of the swing
-provides additional time for viewing the balls trajectory and for determining time to contact
-more accruately predict where ball will be at impact
from a swing-initiation timing accuracy standpoint, why does a baseball player swing near maximum
if swing of bat is sped up, decision about when to intiate hte movement is made later and more temporally accurate
-shortening MT stabilized the initiation time of movement allowing for greater mt accuracy
**decision made closer to ball contact - less time for error
from a mvoement time accuracy standpoint, why do baseball players swing enar maximum
player has to estimate their own movement time to be able to hit ball in the middle of the movement
-if actual mt is different then the estimated = timing errors
**reduced MT increases movement timing consistency
from a movement spatial accuracy, why does a baseball player swing near maximum
when movments are very fast and forcefyl, reducing the MT tends to increase the accuracy rather than decreasing it
-improving spatial accuracy
from a ball impact standpoint, why do baseball players swing near maximum
faster swing gives more impact to ball
who will msot likely win, person initiating or respondng to stimulus
person responding
what is prehension
the act of taking hold, seizing or grasping
prehension and fitts law works for objects in eveyday life as well primarily due to what
increased duration deceleration phase
fitts law and walking with typical populaiton compared to parkinsons disease
TYPICLA
-scale walking to door widths
-slower, shorter steps
PARK
-larger reponse - even slower
-sensitive to visual info
desrcibe the speed-accuracy trade off reconsidered
accuracy does not continue to diminish with increasing speed, instead, the coordination pattern changes so that stability can be reestablished
when increases in speed result in decreased accuracy, the motor system is faced with what 3 alternatives
-reduce the speed and maintain accuracy
-decrease inaccuracy and maintain speed
-main the speed and change the movement pattern in order to reestablish stability
