Fitts Law

A total of 53 subjects (33 females; 20 males) participated in the study. All participants were Kinesiology students at NS University with a mean age of 20.9 (females = 20.5; males = 21.4) with standard deviation of 0.60 for females and 1.8 for males.
A total of 6 tapping boards were used each equipped with a stylus and 2 metal targets. The targets on each tapping board were of different size and separation so that the targets progressively became more difficult for the subject to hit. Attached was a hit counter that counted each tap made by the stylus on the metal targets. A digital stopwatch was used for the purpose of keeping timeof each trial. Lastly a laptop computer was used for the recording of data.
Task & Procedure
FIGURE 1. Subject??™s movement time, index of difficulty and line of best fit.
TABLE 1. Mean index of difficulty (ID) and movement time (MT) for all 6 experimental conditions.
The results indicate that as the index of difficulty increased movement time consequently decreased.
For the exception of 1 of the 3 related studies the literature appearsto agree with the findings of the present study. That is, as the index of difficulty increases,movement time speed decreases. Therefore, it can also be said that the independent variable (MT) does reliably affect the dependent variable (ID).
In Belkinand Eliot??™s study the mean age of subjects was 8.75 years, ranging from ages 6 to 11. The age of the subject??™s in the present study differed significantly with a mean of 20.9 years, ranging from ages 20 to 27. The amount of subject??™s used in the study also differed greatly with Belkin and Eliot only using 16 compared to 53 in the present study. The two studies did however have some similarity in terms of participants, that is both males and females were used with a larger female population amongst the subjects. The tasks differed greatly between the two studies. Belkin and Eliot had subjects attempt to hit a target 25 feet away using a hockey stick and ball. The present study had subjects hit two metal targets on a board as quickly and as accurately as possible using a pen shaped stylus. The procedure also differed in that Belkinand Eliot??™s study divided they??™re subjects into two groups, one concentrating on speed and the other on accuracy. The present study divided subjects into groups but all groups were instructed to focus on the same task. Furthermore, the related study was done over a 3-day period and had subjects do a set amount of trials before they were complete. Whereas, the current study was done in one day and trials were timed so that after 20 seconds participants completed the attempt.
Subjects in the study conducted by Duarte and Latash had a mean age of 32 years, which is significantly higher than the mean age of 20.9 in the present experiment. The study also used a significantly smaller sample sizeof just 10 subjects. The tasks of two studies were similar in that subjects were asked to hit a target as quickly and as accurately as possible. However, the tasks differed as the present study asked subjects to hit the targets with a stylus while in Duarte and Latash??™sstudy subjects were instructed to use their right big toe. The procedure of the two experiments differed in a number of ways. Firstly, each trial in the related study only involved one tap of the target compared to as many taps as possible within 20 seconds in the study conducted at NS University. Participants in the literature also had to complete 5 trials on each of the 6 different target distances. Trials were only accepted in thisif the error percentage was 7% or less compared to 5% in the current study. Lastly, subjects in Duarte??™s study were given practice trials before attempting the real trials, while NS students were not given the opportunity for practice trials.
After a review of the results from the present study as well as the literature itseems clear that the aforementioned hypothesis is correct. That is, as the index of difficulty increases the speed of movement times will decrease or as target size increases movement time speed decreases.
Belkin, D. S., & Eliot, J. F. (1997). Motor skill acquisition and the speed-accuracy trade-off in a field based task. Journal of sport behavior, 20(1), 16-28.
Duarte, M., and Latash, M.L. (2007). Effects of postural task requirements on the speed-accuracy trade-off. Experimental Brain Research, 180(10), 457-467.
Smits-Engelsman, B., Sugden, D., and Duysens, J. (2006). Developmental trends in speed accuracy trade-off in 6-10-year-old children performing rapid reciprocal and discrete aiming movements. Human Movement Science, 25(12), 37-49.