As of iOS8, there are exactly 7 interactions with the iOS screen that actually yield a result. (I am referring to touch gestures. This list excludes interactions with hardware buttons.)
- Perhaps the most common, you can single tap any app to launch it.
- Touch and hold any app to enter the edit mode which allows you to rearrange and delete apps.
- Swipe to the left to move to your next page of apps.
- Swipe down from the top of the screen to pull down the notification centre.
- Swipe up from the bottom of the screen to pull up the control centre.
- Swipe down from anywhere else on the home screen to open Spotlight Search.
All of these have their place in everyday use. However, it is the last interaction programmed into this screen which I find the most interesting.
7. Swipe to the right and this happens:
This interaction serves essentially no functional purpose. In fact, the other day I spent probably 10 minutes just doing it over and over again, wracking my brain to try and determine why a programmer would waste time implementing this. There is nothing else to the left of the first page of apps so why be able to start a swipe in this direction at all?
But then it hit me. For users with many pages of apps, this small nuance in UX Design is essential. When swiping from page to page you may lose context of where you are and attempt to swipe to the next page when none exists. In this instance, there is a gap between the user’s mental model of state and the actual model of state. By providing feedback specifically designed to correct this gap, the user is less likely to make the same mistake twice.
Let me break that down a little further by explaining the difference in user actions between 2 designs.
In Design 1 we will be lazy developers and not implement the elastic snapping. Instead, the apps will simply not move when the user tries to swipe to a page that doesn’t exist. Design 2 will represent the actual implementation of iOS 8, with elastic snapping.
Here’s our scenario: The user is confused and doesn’t realize they are on the last page of apps. The user’s mental model is that they are on the first page of apps. Their goal is to use an app which is on the second page of apps. Thus, the logical sequence of actions the user should take is to swipe to the next page and click on the app.
Design 1. Upon taking the first action (swiping to the next page) nothing occurs. The device appears frozen. The most logical action is to simply try again. This creates a loop of retries until the user realizes what they did wrong.
Design 2. Upon taking the first action (swiping to the next page) the screen moves with the swipe gesture just far enough to reveal that there are no more apps. This feedback shows the user where they are in actuality and corrects their mental model.
As you can see, Design 2 saves one or potentially a long loop of unnecessary actions. It also represents a quick, clean, and polite way to tell the user they did something wrong without resorting to an error message like “There are no more pages to be displayed!”