In 1954, a chap called Paul Fitts came up with an equation to express the ease of pointing to or touching an object. In essence, he stated that this metric was a function of the distance to the target and the width of the target.
This is another example where work done more than half a century ago has direct relevance to many of the things we do today - especially in the area of user experience.
The best mobile apps have killer user interfaces where user journeys are beautifully predicted / calculated, and the activators for common functions are right where the user expects them to be.
Steve Jobs was famously against having an iPhone with screen larger than 4 inches or an iPad with a screen smaller than 10 inches. He believed the 3.5 inch iPhone screen was the optimal size for sitting in the hand of the user - and he may well have been right. However, there is now much more to a smartphone than it's ability to sit comfortably in our hand.
Our phones have got smarter and the range of applications we use them for has grown fantastically. The least used feature on most modern smartphones is the ability to make a simple phone call. One could argue that "personal computer" is a much more appropriate term for the smartphone - after all, it's something that we keep on our person, and has all the power of our laptop. That big beige thing that sat on our desks in decades gone by was only really 'personal' in that you might have one of your own. It later became know as a 'home computer' as it was often anchored at home, while the laptop had become more popular.
People now use their phones for reading documents, books, magazines and newspapers, writing e-mails, browsing social media, taking and editing photos and videos.
All of these things are much more pleasant on a nice chunk of 5+ inch screen. They may not fit quite as comfortably in your hand, but they offer enough screen real estate to support the applications you need to get the job done.
The point is, there is a compromise at play here. We sacrificed the smaller, comfortable, hand size for the extra capability offered by the less comfortable, large devices.
Mobile app design became a real thing - firstly to deal with the small size of the smart phone screen, and then again, to deal with the annual increase of the size of the smart phone screen. Paul Fitts' work sits at the heart of mobile design. The constraints of the smartphone screen size (and in the early days, resolution) and the size of the average human finger, help us to decide just how big our buttons should be, where they should be placed on the screen throughout our user journeys, and even whether the feature is actually worth the screen real estate required to activate it.
A little while ago I was working on a feature in one of our mobile phone apps. There were 2 screens that work together as part of the 'normal journey', and in designing the screens in a popular mock-up application, I had a button that moved the user from one screen to the next and back to the first. Visually, it looked pretty good, and in the mock-up, it also looked like it would function perfectly well.
I implemented the feature and ... it felt clunky. How could a single button click 'feel' so wrong? I thought. If as a user I was working forwards through a series of screens in a wizard style interface, that really needed a positive confirmation in order to move onto the next screen, then the buttons approach would have felt just fine. However, in this particular case flipping back and forth between the two screens was a common use case, so I changed the implementation to a swipe and it immediately felt better.
I'm not sure if there is a term for how one might describe this feeling of clunky-ness or effort required to perform the transition. It's still an application of Fitts's Law as the target area for the swipe is often the whole (or large part) of the screen. I often see (and use) the term 'cognitive load' applied to the act of understanding a user interface - i.e. making it obvious to the user what they need to do to achieve their goal. In this case, the best way I could describe the difference in feel between the button click and the swipe was "muscle load".
The swipe has a low muscle load - the hand is already holding the phone and a minimal thumb motion triggers the action. For the button tap, depending on the location of the button and the size of the phone screen, the free arm may have to be moved into position to tap the button - requiring a more significant motion or muscle load.
Whilst in general, for the benefit of your users, you should be aiming for the easiest possible user experience, there are times when you can reduce accidental activations by deliberately using a trigger that requires higher muscle load.
No comments:
Post a Comment