I’m not an expert in human-computer interaction (hereby referered to as HCI). I can’t rhyme off every best-practice interaction design principle, nor do I have all the best UX patterns memorized. I am still an amateur trying to break into the field. However, I do have a knack for noticing annoying things in websites and apps, and it’s always nice to find a design principle that explains why a certain behaviour can annoy a user.

Today’s example of intuition-to-principle comes to us from Instapaper. I got on the Instapaper bandwagon a bit later than most people – as in I started using it last week. So as I’m playing around with it today, I wanted to delete one of the articles I had saved and subsequently finished reading. Now, to their credit, what happens next  isn’t entirely a bad thing. When you delete an article instead of archiving it, a little message window pops up asking you if you want to ‘permanently remove this item from your account’. This is a good thing, but what sucks is the placement of the pop up.

Because Instapaper is using what seems to be a simple javascript alert to accomplish this, the alert appears in the middle of your browser window. This accomplishes the task of letting the user decide to cancel deletion, but in a disruptive manner. Why is it disruptive? Not only does the alert prevent you from continuing until you deal with it, but you have to move your cursor from the item you were deleting, to the prompt. It may not seem like the biggest deal, but when you’re deleting lots of items, the time it takes to mouse back and forth gets annoying quick.

The fun part of all this, is I’m not the first person to discover the fact that the time it takes to move your mouse around the screen can degrade a user’s experience. Fitts’s law, according to wikipedia, ‘is a model of human movement in human–computer interaction and ergonomics that predicts that the time required to rapidly move to a target area is a function of the distance to and the size of the target’.

Designers have been keeping Fitts’s law in mind for a while now, because a reduction in time taken to perform a task causes an increase in perceived efficiency and ease-of-use.  So as it turns out, you don’t need to know every design principle in order to enhance the user experience of a product, but know a few here and there can help you explain why there is a need to change in the first place.