Fitzpatrick Law also has a time when it doesn't apply.

Fitzpatrick law refers to the time that a user uses a pointing device to reach a target with the following two factors, distance and target size.

(1) The distance between the current position and the target location of the device (D). The longer the distance, the longer the time spent; 2. The size of the target (S). The larger the target, the shorter the time spent. The law can be expressed in the following formula: T = a + b log2 (d/s + 1)

The nearer the distance, the larger the target and the shorter the time required for the click. This seems to be a good understanding and easy to use in design. But when you use the Fitzpatrick law to measure all the designs, you'll find some problems with the interaction experience.

One of the Fitzpatrick laws: larger clickable regions

The main theory of Fitzpatrick's law is that the larger the click Area, the less time it takes to hit the target.

Advantage: The larger the clickable area is, the easier it is to operate, because the user's mouse can touch easily.

For example: Some Web button clickable areas are ridiculously small. The result is that the user needs to move the cursor exactly to the link to produce a response. Fitzpatrick Law suggests that designers try to increase the clickable area of the button as much as possible, giving the user a better experience.

The left clickable area is small, the right clickable area is large, and the right cursor can be clicked more quickly to the button. (The case on the left is Firefox, and the right case is Apple).

It is a good idea to increase the clickable area of the button and to guide the user to perform certain actions, which is one of the methods commonly used by designers.

For example, when designing the main button of the interface, the button is often made very large, Fitzpatrick law provides a strong theoretical basis for this.

Disadvantage: Click the area is the bigger the better? The larger the click Area, the more screen space will be used to disrupt the balance of the interface. When the interface space is not very crowded, it is feasible to enlarge the clickable region. However, when the click Area is enlarged to a certain extent, it has nothing to do with usability.

A small button to enlarge it by 10%, and its usability will be significantly improved, but if you add a button that is already very large to 10%, it is not proportional to usability.

Fitzpatrick Law bis: Reducing the movement of the cursor

The nearer the distance, the shorter the time required to click on the target, which is the second largest theory of Fitzpatrick law.

Advantages: The user commonly used functions placed in a region, compared to those placed separately, users can reduce the movement of the cursor, faster to complete the operation.

For example: The Ubuntu Unity interface, the top of the screen is the search box, the lower end is the file type filter. Two filter areas are very far apart, and users need to operate in two different areas when browsing information.

(Fitzpatrick law does not agree with this practice, because they should be adjacent to each other.) Case: Ubuntu Unity, screen capture: webupd8.org)

Disadvantages: If strictly according to Fitzpatrick Law to design, may be in conflict with other design theory, such as: according to different content and function to organize information, so that the interface information neat and reasonable, users can easily find the content needed.

Here's a picture of different types of operations arranged in a very small interface, the left is a desktop tool, the right side is the file insertion tool.

This sort of left-right approach makes the interface neat and organized. (For example: Numbers)

Users will have a familiar mental model of organized classification. After using once, you can clearly remember the function of the left and right sides of the functional area. Conversely, if the interface design uses only the button usage rate to arrange the interface layout, then the layout way will be completely different.

Another principle that conflicts with the Fitzpatrick law is that the interface does not look messy. The Pull-down menu is an effective form of consolidating the content of the site. Although some designers will disagree, the benefits of the Pull-down menu are undeniable.

The Pull-down menu makes your interface look clean and not messy.

The Fitzpatrick law does not recommend using a Drop-down menu because the cursor needs to move a long distance to reach the user's option. First, the user needs to click or hover over the drop down menu, and then move the cursor until the option he wants is not too fast, but the flaw is less than the multiple advantages of the Pull-down menu.

The third important principle of conflict with the Fitzpatrick law is to design an interface that allows users to make mistakes, helping users reduce the cost of error. Fitzpatrick Law suggests that designers put together some common functions to reduce the movement of the cursor while also saving some of the interface space. But the cost of saving the interface space is the mistake operation of the user. When the edge of the button is not easy to identify, users are prone to misoperation.

The way the interface element is placed directly determines whether the error will occur. (For example: blurb.com)

Note that if you share or edit this type of functionality, the cost of misoperation will be high and users will hate you.

When the user accidentally turns on the wrong link, he can click the return button to resume his previous operation without causing any serious consequences to the user. So, at this point, the link can be placed in a relatively random position.

And in some cases, the problem is annoying. When the user plays a video screen or audio file, inadvertently point to stop, exit, the next or clear playlist, he can no longer easily restore the previous operation.

When it comes to editing or sharing functions, the problem is more lethal. Mistakenly click to send print delete download upload burn shut down link disconnect receive or reject, user behavior may cause some irreparable consequences.

Therefore, when designing buttons for special functions such as editing and sharing, designers must try to find ways to avoid the misuse of the user.

1 provides the user with an action to undo the execution. (such as a temporary cancel button)

2 Leave a little space between the two interface elements.

3 makes the edge of the button easy to identify.

4 prominent emphasis.

5 Group the buttons by function.

Finally, for instance,

If you want to "receive mail", but accidentally delayed to "create a new message", this will not cause any serious consequences, but do not put the reply and delete button too close.

Two-step input method can effectively prevent the occurrence of errors, it is contrary to usability, but effectively prevent users from misoperation. Because the user will mistakenly operate to any one of these actions, but it is not possible to simultaneously mistake them successfully. such as sliding delete.

Slide first, then delete. Every mistake that is very easy to make, combined can be an effective mechanism for preventing errors.

Users will inadvertently slide to and from the left, will not be careful to remove the button, but they will accidentally slide after not carefully click to delete the button? The odds are very small.

The two-step input method is widely used in mobile devices, because mobile devices use the scene more complex and often have misoperation.

At design time, you can first hide the second part of the user action, and then the second step occurs when the user finishes the first step.

So, when sliding and sliding, sliding and clicking the combination of both, the user to operate more than directly press a big button trouble, but this is necessary.

Fitzpatrick's Law III: avoiding muscle tension

The purpose of the Fitzpatrick Law Performance index is to determine the information capacity of the human motion system. In other words: It determines the way the operation is done by determining the amount of physical energy the user needs to operate.

Benefits: When we operate a complex device, the benefits of simple input are obvious. The most prominent example is the vertical touch screen.

Using the Fitzpatrick Law theory, you can make the vertical touch screen interactive experience better. (For example: perceptive Pixel)

When the touch screen is operated, the vertical direction of the arm will cause the deltoid muscle to become fatigued quickly. This can result in input errors or force the user to abort the operation. Therefore, avoid the complex input method can prolong the user's operation time.

Disadvantages: Complex input methods can prevent errors. For example: Mobile devices are often placed in pockets, often causing unexpected operations. In this case, the High-precision input method is very useful. At the same time, these high-precision input methods also remind users of the severity of these commands. For example, the iphone is closed.

If this operation will have serious consequences, choose to slide the operation, instead, select the button.

Shutdown or restart the device is relatively serious consequences, once triggered, you can not undo. Therefore, it uses a sliding that requires high-precision operation. On the contrary, the cancellation is relatively no serious consequence, so it is designed as a button.

Sliding controls and other gestures that require high precision are very safe and cumbersome to enter. Therefore, in order to balance the relationship between security and usability, they are often executed with some serious but infrequently manipulated commands. such as: Screen unlock, shutdown, set up the system, perform administrative tasks or wake-up alarm equipment. When the consequences of some of the commands will be frequently manipulated by the user, such as editing delete or transfer files, there are interval icons and two-step input method is very effective.

The second reason is that gestures can save some space in the interface. However, according to the Fitzpatrick law, it involves a certain degree of drag that makes the muscles in a tense state, which is why the Fitzpatrick Law recommends clicking and pointing. It is also good to drag and drop gestures that are unfavorable to the Fitzpatrick law, and it does not require interface controls.

For example, you manage a Deviantart art collection. Add Items to Favorites, you don't need buttons, instead, you just drag the picture and the box will show you how to drag.

Drag-and-drop operation forms do not need to occupy the space of the interface, because it does not require a button or other UI elements. But there are drawbacks to this type of operation, and it does not provide a clear visual clue to the user. Users are likely to ignore or not know their existence.

Fitzpatrick's Law IV: using the main pixel

The idea of using primary pixels is to have pixels in a particular location on the screen, and it's easier for users to click on them, such as the edge of the screen. However, the quickest way is to directly click the right mouse button, as long as the surrounding specific elements to click on the right to get the appropriate options, do not need to move the cursor a long distance.

Advantage: You can get contextual options by clicking the right button around text-specific pixels, so you don't have to move the cursor over long distances. There are two types of text menus: linear menus and pie-like menus.

The Fitzpatrick law is more inclined to the pie-like menu. Reason: The pie-like menu provides a large clickable area. Second, because the menu is a circle, the cursor arrives at any location in the menu at the same distance. This consistency allows the user to create a memory of the strength of the muscle when it comes to the option. On the contrary, the linear menu has only the first few options cursor is very easy to reach, which is why we want to put the common options at the closest point of the cursor.

(Fitzpatrick Law is more inclined to pie-like menu)

When an item is on the edge of the screen, the user can move the cursor directly to the edge position, and it is easier and faster to hit the target area than to place the option in the middle of the screen.

Disadvantage: The pie menu has a slight advantage over the linear menu in time and error probability. But in the actual design, the pie-like menu is not considered.

Although the Fitzpatrick law is more biased toward a pie-like menu, its drawbacks are enough to obliterate the virtues.

The pie menu causes a lot of options when the area becomes very small. The solution to this problem is to remove the unwanted option, which conforms to the Marschik law.

Second, the submenu is a good way to have a lot of options. The Pie menu may also add submenus, but this can disrupt the screen structure and make it look messy and disorganized. This is the obvious advantage of a linear menu over a pie-like menu, and a linear menu can make it easier to organize the hierarchy with a submenu.

Finally, the pie-like menu takes up more space. Can cause two problems: first, masking options, and second, when the cursor triggers the four edges of the screen, they are more likely to be in the pop-up than the current cursor position.

In short, as a designer should be more inclined to use a linear menu, rather than a pie-like menu.

1 must have a whole lot of options

2 Must use submenu

3 Combination of menu items

4 screen is the most important

Finally, when using the mouse to manipulate the device, there are two potential problems that have to be mentioned. On a large screen, the cursor needs to move a long distance, which can almost offset the advantages of the edge of the screen. Web designers cannot benefit from this rule because their content tends to go beyond the screen, and they have to choose a more compact central layout.

When you use a touchscreen device, placing an interface element on the corners of the screen will not speed up the interaction, but it may even have a negative effect. Clicking on a four-corner area requires frequent use of the arm by the user, which makes the arm feel fatigued quickly. Therefore, it is in accordance with Fitzpatrick's law that the elements are placed in the easiest place where the user's hand can be reached, making them more comfortable to use.