Mobile usability testing: Fat finger syndrome and touchscreen UIs
Fat finger syndrome – Inadvertently triggering a secondary action when navigating a touchscreen UI
When it comes to mobile usability testing, fat finger syndrome continues to cause problems. Although some might be tempted to lay blame at the door of the user, whether for being clumsy or inattentive, the truth of the matter is that fault lies squarely with the UI. After all, isn’t the job of a good design to eliminate all the factors that might confuse or frustrate the user, ergo offering a compelling user experience?
On several occasions in the recent past, I have come across a layout during mobile usability testing, where the designer has seen fit to use a hamburger to represent the menu, placing it alongside the logout icon. It doesn’t need me to spell out where this is headed, suffice to say, having to log back in is a sure-fire way of testing a user’s patience.
Where this issue arises, a lack of consideration regarding target zones, the spacing of elements and how this all renders on the smaller screen, appears to be at fault.
So, without further ado, here’s a few points to remember if you don’t want fat fingers getting in the way of your design:
- Keep touch targets large – Within reason, of course, but the greater the area, the less chance of user touch error
- Recognise input methods – Users employ their finger pads, fingertips and thumbs when interacting with a mobile touchscreen. Remember this when designing icons, sizing touch zones and incorporating whitespace
- Target screen position may dictate which digit is used – An element’s position on the screen can influence whether the user adopts a single or two-handed approach, with the thumb being used to make a selection in the former. It is easier for a user to stretch their thumb to the far side of a screen, than to contract it to the near-side, which compromises the balance of the device
- The average user’s finger width in pixels – 45-57 px
- The average user’s thumb width in pixels – 72px
- Thumbs remain the most popular input method – 49% of users manage their device single-handedly, with 67% of these using their right hand. Of the 33% that cradle their device in one hand and interact with the other, 72% use their thumb
Mobile usability testing and avoidance of fat finger syndrome is an essential part of website and app development, so always validate your designs before releasing them into the wild.