The principle requires us to recognize and to take into consideration that to be human is to be fallible. When applied by designers, the forgiveness principle can be expressed in two complementary ways. The first is that design should have good affordances to help users avoid making errors. The second is to help users minimize unintended consequences or better yet fully recover from errors when they occur.
An illustrative example of this comes from Bruce Tognazzini, editor of the first eight Apple Human Interface Guidelines. When designing new and exploratory interfaces, he argues strongly for incorporating forgiveness and highlights three of his own principles. These include providing users reversible actions, an escape hatch out of the current path, and a sufficient amount of guidance while remaining out of the way.1 His guidelines have been shown to withstand the test of time. The iPhone for examples demonstrates these qualities despite launching nearly three decades after Bruce’s departure from Apple. In the iPhone interface, even the most complex settings are simplified down to a toggle or menu selection that users can dynamically change anytime. One can always return to the home screen with a single button press or in the latest models a single swipe. And knowing it’s easy to “go home” fostered a willingness to explore and learn the new design which included the new smartphone gesture of pinch-to-zoom.
Example of the principle cited by one of my sources: Bruce highlights a funny story in retrospect about Xerox Star, a desktop GUI in the early 1980s. At the time dragging a document icon onto the printer would initiate printing out the document. However, once printed this single action also permanently erased the file from the computer. Engineers rationalized this by claiming the document was now in physical form and hence the electronic file no longer served a useful purpose. Designers ultimately advocated different and won the argument and today these two intents, printing and file deletion, have been separated into two distinct actions.2
Example of the principle not cited by one of my sources: In a Medium article Anton Nikolov provides us with an example of the forgiveness principle applied to physical goods. He highlights NikeiD, an online shopping experience that lets you customize colors and graphics on shoes for preview before placing a direct order with Nike.3 While there are no returns on customized shoes and thus no ability to recover from an error, the online experience allows previewing to help minimize potential errors in the first place.
Example of the principle not cited by one of my sources and not located online. I found that my building’s telephone entry system incorporated the forgiveness principle in multiple ways. Known more commonly as a call box, it allows visitors to call residents who can remotely unlock the main building door. Upon approaching the box, visitors are immediately greeted with instructions to scroll and locate the intended callee. While it doesn’t explicitly mention the up and down arrows, there aren’t many other keypad buttons that suggest a scrolling action. Once scrolling is initiated, building residents are listed in alphabetical order by last name and first initial. This aids in identifying the correct individual. The “CLR” button can be used to immediately terminate a call should the wrong resident be dialed. Lastly, though not apparent residents can use the call box to let themselves in if set to ring their mobile number. The first two items, a welcome instruction message and listing residents by last name, serve as good affordances to help visitors perform a desired action: calling the right resident. The later two, a CLR button and dialing oneself, provide a safety net to help mitigate unintended consequences.
Footnotes
1. Tognazzini, Bruce. “First Principles of Interaction Design (Revised & Expanded).” asktog. Last modified Mar 5, 2014.
2. Tognazzini, Bruce. “First Principles of Interaction Design (Revised & Expanded).” asktog. Last modified Mar 5, 2014.
3. Nikolov, Anton. “Design principle: Error & Forgiveness.” medium. Last modified May 27, 2017.