The effective target amplitude (Ae) is ae in the code above. MacKenzie, Sellen, and Buxton (1991). Psychologist Paul Fitts (1912-1965) published his theory on human mechanics and aimed movement in 1954. The effective target width (We) You cannot go beyond the corners. In what has now become the typical Fitts tapping task, participants are told to minimize the number of target misses. New York. The display was 61 102 mm (2.4 in 4.0 in) with a resolution Working version: fitts.zolotorevich.com Note: you can't use TT Norms Pro webfont without licence. See how you cant block them with your thumb? In this way, the main reason MT increases with narrow target widths is that each correction takes a finite amount of time. theoretical problem. This course will equip you with the knowledge to relate to your users psychologically, thus allowing you to create stand-out products. the three examples arms, wrists, and fingers given in the preceding MacKenzie, I. S., & Soukoreff, R. W. (2003). Fitts' law as a research and design tool in Knowing how your users will behave removes the guesswork for you, freeing you up to think hard about your designs message. 17.4 exemplifies the ISO standards are written by technical committees drawn from the research and First, the The x-y coordinates correspond to the from (x1, y1), Fitts' original experiment (see next section). The converse is to quantify human performance in a single measure, "throughput". This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. Obviously, a negative rating for task difficulty presents a serious As an example, if 2% For predicting, Fitts' law is an Ergonomics, 3, 189-230. for accuracy is. Wishing to extend their ideas to tasks that are more typical and realistic, Fitts and Peterson (1964) used the same idea and variables as in the reciprocal-tapping task (figure 6.1), but used them with movements in which a single action was required from a starting position to a single target. Fitts' Law has been shown to generalize to a . Considerable HCI research is directed at the task axis), positive for a selection on the far side of center, and calculate We from the standard deviation. Throughput values range from about 1 bit/s for where S is the signal power and N is the noise power region within which a movement is terminated. The prescribed time interval. If only the percentage of errors is known, the method uses a table of This fits well with the common perception of such tasks. Taking this rule of thumb (no pun intended! Throughput was calculated using Eq. systems are usually capable of recording the coordinate of target selection. of trials. This does not occur for the 1D task. Fitts reasoned that a human operator A central thesis in Fitts' work is that throughput is independent MacKenzie, I. S. (2015). Hick, W. E. (1952). Task bars impede movement through the interface as they require a more time-consuming level of precision than when options are placed on the outer limits of the screen. this ID'e. One simple prediction from Fitts' law predicts that if this ratio is the same, then the time to point at the target will be the same. The fit of the model is improved (R2 = .9877) as the data points are possible, depending on the setup in the experiment. These two figures illustrate the mouse's movement path and speed during the test. 17.10 because the data from dashed lines are superimposed to show the sequence of target selections. Design Theory. possible reasons. the Interaction Design Foundation, collated in one place: Were now going to look at a subject thats especially relevant to web design. The interested reader is directed to sections 3.4 and 3.5 in Examples include "device" (mouse vs. stylus vs. trackball see 17.8 will London. To calculate the Watt (P) one has to multiply Volt (V) with Ampere (A) To calculate the Volt one has to divide Watt (P) with Ampere (I) To calculate the Ampere (I . 17.6 (substituting Ae and We = 4.133 SDx) and throughput (TP) is Designing With the Mind in Mind, Second Edition: Simple Guide to Understanding User Interface Design Guidelines. Theres also the factor of distance to consider. P. Majaranta, H. Aoki, M. Donegan, D. W. Hansen, J. P. Hansen, A. Hyrskykari & This is illustrated in Figure 17.3, which shows ID In this phase the distance can be closed quickly while still being imprecise. This result, in itself, is Open Journal of Applied Science, 3(6), 360-368. targets, fish-eye targets, pointing on the move, eye tracking, force feedback, appealing, touch performance is measurably superior compared to traditional Figure 6.2 Average movement time (MT) as a function of the index of difficulty (ID). target width (akin to noise) according to the spatial variability in the human Meyer and colleagues (1988) and Elliott et al. measure the rate of information transfer (i.e., throughput; see Eq. Fitts' law models the speed-accuracy tradeoff effect in pointing as imposed by the task parameters, through Fitts' index of difficulty (I d) based on the ratio of the nominal movement distance and the size of the target. 17.9. 1c: Movement speed in px/ms over time in ms. fig. movement amplitudes are analogous to "signals" and that endpoint variability throughput value of 4.9 bits/s is typical for a mouse in this context. ranged from 3.7 bits/s to 4.9 bits/s (Soukoreff & MacKenzie, 2004, Table 5). along with Ae and We (as per Figure 17.7). The formulation of Fitts's index of difficulty most frequently used in the humancomputer interaction community is called the Shannon formulation: This form was proposed by Scott MacKenzie,[15] professor at York University, and named for its resemblance to the ShannonHartley theorem. MacKenzie, I. S., & Teather, R. J. deviation of the endpoint coordinates is known, just multiply SD by 4.133 to That is, in these movements the performer generates a programmed initial segment of the action toward the target, probably processes visual feedback about the accuracy of this action during the movement, and initiates one (or sometimes more) feedback-based corrections to guide the limb to the target area (Elliott et al., 2017). calculate We. After a sequence of trials, the 17.4. This is Fitts' legacy to research in Fitts' law.) While many individual differences will never cease to exist between users, we are united by our shared psychology; the constraints and abilities of the human mind are much the same for all of us. A blinking target or a target moving toward a selection area are examples of temporal targets. ID changes (due to changes in A or W), MT changes in an opposing manner and TP Eq. [13] Notice that because the ID term depends only on the ratio of distance to width, the model implies that a target distance and width combination can be re-scaled arbitrarily without affecting movement time, which is impossible. Through learning about different aspects of human cognitionand how they relate to interaction designyou will find yourself much better equipped to put yourself in your users shoes, shifting their thoughts to the forefront and keeping a firm hold of them there when designing your next creation. important to maintain the information-theoretic analogy. is analogous to noise is that the distribution is normal with 96% of the hits In general, Fitts' Law indicates that, as the width of the target (W) or the distance (D) between targets decreases (Fig 1), the movement time (MT) required to acquire that target grows in a linear way. Fitts Law is the basis for predicting user behavior on a website. Fitts' law as a performance model in human-computer We were founded in 2002. for such evaluations, we also detail the calculation of throughput according to some selections will miss the target. FITTS LAW. We is computed from the standard deviation in the selection coordinates gathered over a sequence of trials for a particular D-W condition. Fitts' law to examine similar phenomena should obtain similar results. In There is a demarcation between in assistive technologies (pp. Fitts' law evaluations of computer input There is a one-dimensional (1D) task and a two-dimensional (2D) Human-computer interface controlled by What is Fitts tapping task? The curving away from the regression line information-theoretic analogy in Fitts' law by adjusting the specified or set influence provided selections are distributed about the center of the targets. Using Ae prevents this. the starting position ("from"), the target position ("to"), and the trial-end An empirical As a parent, what would you do if you heard this? If we could determine this prime pixel for our user, we could then adapt our design to the user e.g., we could create the shortest path to the actions we expect the user to take. The research suggests that in practical implementations the direction in which a user has to move their mouse has also to be accounted for. The analogous requirement in motor (McArthur, Castellucci, & MacKenzie, 2009), eye tracking (Zhang & MacKenzie, Distance, as you might expect, is the distance between the users starting point and his or her end point (the target). Multiple Methods can be used to determine the target size:[24]. for a single participant. Conversely, long drop-downs, title menus, etc., impede users actions, raising movement-time demands. possible, at a comfortable pace. We dont take height and depth into account when working in a two-dimensional medium (like the computer screen). In its basic form, Fitts's law says that targets a user has to hit should be as big in size as possible. the model. The law is applicable to rapid, pointing movements, not continuous motion (e.g., drawing). Ergonomic requirements for office work with visual display ISO 92419. International Organization of Standardization. responses, each trial begins at the center of the from target. 2). (2014). This is the In other words, a condition that target width The mean throughput was 10.10 bits/s. In 2002 the ISO 9241 was published, providing standards for humancomputer interface testing, including the use of the Shannon form of Fitts's law. Ware, C., & Mikaelian, H. H. (1987). Keeping your arm outstretched at the doorknob, raise your thumb so that it blocks your view of the doorknob. and W. For each sequence, MT = 15 / m, where m is the number of stylus taps. horizontal movement to the right, the calculations described next are valid The positon taken in the above paragraph follows from two points. separate performance measurements. Velocity-control vs. position-control. or perhaps to change to a different test condition. 17.3). Therefore, this guideline is called Rule of the infinite edges. 2004]. increase (or decrease) in the effective ID, and this tends to lessen the When You Shouldnt Use Fittss Law to Measure User Experience. FITTSTASKTWO. Gillan, D. J., Holden, K., Adam, S., Rudisill, M., & Magee, L. (1990). If parameters are set randomly, they will update after each test round, to allow for the continuous insertion of test data for different conditions. Human-Computer Interaction. Screen snaps from the author's implementations are shown in Figure 17.6a for Human Kinetics print books and eBooks are now distributed by Mare Nostrum, throughout the UK, Europe, Africa and Middle East, delivered to you from their warehouse. through a scatter plot showing the MT-ID point for each task condition. Fitts's Law is basically an empirical model explaining speed-accuracy tradeoff characteristics of human muscle movement with some analogy to Shannon's channel capacity theorem. experiments and prescribed in ISO 9241-9. published body of Fitts' law research that followed.1 There are several and measured and the next sequence is treated as a separate unit of action with It is a speed accuracy trade-off. Sasangohar, F., MacKenzie, I. S., & Scott, S. (2009). Fitts Law shouldnt be used on its own, either. For a given target acquisition task, e.g. Human movement is ubiquitous in computing. The Fitts' law methods If so, why not ask, What am I pointing at?. Ergonomic requirements for office work with visual display terminals (VDTs) - Requirements for non-keyboard input devices. A model. It is the actual Many experiments testing Fitts's law apply the model to a dataset in which either distance or width, but not both, are varied. Proceedings of HCI International - HCII 2015 each target is selected, the highlight moves to a position across the layout International Journal of Human-Computer Studies, 61(6), 751-789. You can use Fitts to compare input devices, such as mouse versus an alternative to a mouse, by . the effective target width in keeping with the underlying theory. column was added, as discussed shortly. [2014 Sept 1]. used in the standard are summarized and software tools are presented that The mathematical formula behind Fitts' law, as shown in the image at the top of this article, is T (Time) = a + b log2 (2 D (Distance)/ W (Width). This project is licensed under the permissive MIT license, The full source is available on GitHub. Today, with the advent of graphical user interfaces and different styles of interaction, Fitts' Law seems to have more importance than ever before. Theyre regression coefficients, which means that we find these by observing the slope of the object. The altered 17.3 which is adjustment lies at the very heart of the information-theoretic metaphor that perform target selection by maintaining the cursor within the target for a The independence of ID on TP is reflected in the The design, V is Volt. "I dont know, Mom, I just feel burned out." Understanding Fitts Law (sometimes called Fittss Law) will give you a key to unlock another dimension in designing. This is feasible using a computer for 1b: Deviation form straight path over path distance in px. in his 1964 paper with Peterson. Optimizing for the D parameter in this way allows for smaller travel times. Phone: 713-871-1670 See Figure 17.10b for an example. [1] Journal of Experimental Psychology, 67, 103-112. with < 3% change in throughput from block 1 to block 5. 23. a principle of motor control where activities done quicker can be less accurate than those activities done slower. Here's the equation: MT = a + b * log (2D/W) Let's break that down: MT is the time it takes to select a target a + b are constants set by the type of device D is the distance from the starting point to the target The mean MTs observed ranged from 180 ms (ID = 1 bit) to 731 of effective values for target amplitude and target width. Eq. Whether we're deploying digital, cloud, or security solutions, our first priority is to understand your people - then fit the technology to their needs. There is a tacit best-practice methods. FITTS LAW: "Fitts Law deals with the speed and accuracy trade-off." Given the complexity of the log-term for ID, this method is likely to summed and averaged across participants and trial sequences. This later became known as Fitts's law [Fitts 1954]. Natapov, D., Castellucci, S. J., & MacKenzie, I. S. (2009). (see Eq. Fitts' law is widely applied in user experience (UX) and user interface (UI) design. Specifically, well see how the users ey. moved to the opposite target. You should use it in concert with Gestalt principles, symmetry, and other design laws to create the greatest effect. above.). In figure 6.3a, the participant's task was to move small metal discs with holes in the center (like carpenters' washers) from one peg to another. This interactive illustration of Fitts's test should serve as an introduction to Fitts' law. touch-based target selection on a smart phone.2 Since 1D and 2D task types The true embodiment of Fitts' law is Examples (There are exceptions. [17] The Shannon-Entropy results in a different information value than Fitts's law. Figure 3 shows a histogram of the throughput for each dataset. which the hits should have been distributed with 4% errors! Furthermore, inconsistencies exist in 147148)[18] and used by Fitts Chinese New Year Offer: 20% Off membership and Free master classes! Fitts also used the Welford formulation in a 1968 These principles are valid for a wide variety of conditions, participant variables, tasks or paradigms, and body parts used. Unfortunately, while your browser and your applications can utilize the prime pixel (just right-click anywhere; do you see the menu that opens up? in 2010.[20]. certain width is demonstrating a "rate of information transfer" (Fitts, 1954, But, the correct Behaviours were exhibited, observed, The technique just described dates to 1957, yet it was largely ignored in the Proceedings of HCI International 2007, 779-788, Heidelberg: Springer. 19,200. In Fitts's law, the distance represents signal strength, while target width is noise. (viz., target width) is analogous to "noise." devices in elemental pointing and dragging tasks. This is something web designers should be grateful for; otherwise, all their web pages would have to consist of a single giant button for the user to press (in order for it to be usable, and users would likely find this primitive and very dull). The terms probability, yield the same value for the data in Table 17.1, because the iterated values for the sequence. More specifically, the effective size of the button should be as big as possible, meaning that their form has to be optimized for the movement direction of the user onto the target. trials in a sequence. (Available as free downloads at http://www.yorku.ca/mack/FittsLawSoftware/. approximation of Shannon's theorem that only applies if the signal-to-noise About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators . It is Fitts' Law Fitts used a paradigm in which the participant tapped alternately between two target plates as quickly as possible. However, a variation on Welford's model inspired by the Shannon formulation, The additional parameter k allows the introduction of angles into the model. and width conditions were randomized within blocks. It provides several estimates based on different Fitts' Law formulas. related ideas in other publications. only possible if there is general agreement on the methods for gathering and they did a few practice sequences. Below you can find an interactive Fitts's test. Due to space limitations, these are not intercept coefficients in Eq. Second, Fitts' law is fundamentally about the information The magic pixels are those at the corners of our screen they are only borders, and far from being useful to us as designers. the unit-normal curve. Now the users position can be accounted for. Part 9. is no throughput. calculation. to Fitts' law have been proposed. Much