When we first built Kerika, we deliberately modeled the user interface using the desktop application metaphor: projects were organized in folders, and mouse actions were as follows:

• Select an item on the page with a single mouse click.
• Open (or launch) an item on the page with a double mouse click.

It seemed the most natural thing in the world to us: everyone on the Kerika team liked it, and we assumed that our users would like just as much.

So it came as a very considerable surprise to us when we observed a generation gap among our beta users, in terms of what they considered to be the most natural way to open and launch items.

The breakpoint is roughly at the 35 years-old mark: people older than 35 had a strong preference for the double-click metaphor, and people under 35 had an equally strong preference for the single-click metaphor: where you select an item with one gesture, and then you select the action you wish to take from a menu that pops up.

The preference grew almost exponentially in intensity as you moved away from the 35-year breakpoint: people in their 50s, for example, had a very strong preference for double-clicking, while people in their early 20s were, for the most part, surprised by the notion that a double-click might do anything at all.

Our theory for this phenomenon is simple: roughly 15 years ago, the Netscape browser came into wide use. People who are older than 35 started their careers before the Web, and first learned to use desktop applications before learning to browse the Web. People under 35, on the other hand, probably first learned to use computers by surfing the Web at college.

(You might guess from all this that the Kerika team’s average age is well over 35, because it never occurred to us that the double-click metaphor might be strange or unappealing to anyone.)

At any rate, Kerika now supports the single-click metaphor exclusively – at this time. The initial feedback we got from our beta users was skewed by the younger demographic, and this caused us to reluctantly abandon the double-click in favor of the single-click. However, we are now hearing more from older users, and a future version – very soon! – will support both the single-click and double-click metaphors.

And while the Kerika application doesn’t run completely smoothly on iPads – for one thing, the Google Docs application doesn’t really run on iPads – supporting the single-click metaphor positions us to ensure that Kerika will run, intact, on tablet computers in the near future.