February 22, 2007

Usability Thoughts To Go...

Shown below is the front of a coffee dispenser I saw on a recent trip (with the critical part enlarged).

(click on picture to enlarge)

The label manually attached to the device tells users to “please pay attention to the display”. As it seems, it was not enough simply having the display there, which provides instructions on which steps to take. Some of these steps are essential in respect to the goal of getting the desired beverage (e.g., when the user is asked to decide whether extra sugar shall be added).

Even though the display is illuminated, people seemingly did not pay proper attention to it, which resulted in interaction problems.
Areas Competing for Users' Attention
This may be in part due to the fact that it is hard for a small display to “compete” for users’ attention with a large area (with all the buttons) in which they perform the interaction. Put in other words: users provide their input in an area different from the one where the system provides (a lot of) it’s output and very far away from the place where the final output (beverage) is provided.

Users' Top-To-Bottom Taskflow Model
Users may even approach the machine with a top-to-bottom taskflow model in mind:

  • Top: Read display first
  • Middle: Push button(s)
  • Bottom: Get cup with beverage
The fact that a look at the display in-between contradicts this strict top-to-bottom flow may also contribute to the necessity of putting a label on the device to remind users of the importance of the display.
A Potential Improvement
It would be interesting to see how users interact with the same device if the display was not constantly illuminated but only when a new message is shown, long enough to read it (a problem of its own) and the fade to dark or less illuminated. Light changes tend to provoke automatic “orientation reactions” and maybe this could be a way to improve interaction without having to attach additional labels on the device. Increasing the size of the display would not hurt, either.

Or one completely overhauls the device and equips it with a touchscreen, where users provide their input in the same place in which the system provides its messages. But the interaction concept for such an "iCoffee" would go beyond the brief thoughts I tried to sketch here…


Duncan Drennan said...

I actually quite like your idea about the top-to-bottom flow of control. Having a look at the picture I'm guessing all the buttons down the side are different beverages. How about this....

Remove the display. Shift all the buttons that are there upwards. Add another set of buttons say two for sugar and two for milk, maybe with a little counter display next to them (a 7-segment type). All of the buttons are the same illuminated type as used for the beverage choice.

Before the beverage has been selected only the beverage buttons are illuminated, once selected, the next section of lights (say sugars) is illuminated and the beverage button lights are turned off. The user selects the number of sugars (up counter, with a continue button), once done the next set of lights illuminates (say milk quantity) and the sugar lights go out. Milk works the same way as sugars. After that the beverage is dispensed. The button of the original beverage selected can flash while it is being dispensed.

How many more functions does one really need on a coffee machine? You mention that the display shows a LOT of info - is it possible that there are just too many options?

khailee said...

dude your blog really rocks. i mean it. i do user-experience design for web apps and im in love w this kind of analysis. learning a lot from your posts, do keep it up.

Mark said...

The idea of the “guiding light” is a nice one. This takes the idea I’m describing (illuminate the display when an important message appears) one step further. (I aimed for an intervention requiring limited changes to existing hardware…)
I can imagine that the overall user experience with your interface would be a pleasant one because the device “takes you by the hand” and clearly shows you which parts of the panel to focus on next. A “coffee wizard”, so to speak…
Since the overall process is not overly complex and long, the wizard approach would probably also be OK for “power users”, who are often critical towards wizards because they like flexible access (“I want to determine in which order I select the ingredients for my beverage”…).

A modification of your idea would consist in omitting the “Continue” button for individual selections, combine sugar and milk in one section and provide a single “Order Beverage” button that triggers the machine to provide output (beverage) based on the current choice. The sequence would then be
- beverage area illuminated
- select beverage
- sugar / milk area illuminated
- select quantities of sugar / milk
- press “Order Beverage” button
This would save one “Continue” button, which may not be much of a difference in terms of time / buttons needed but may result in a “smoother” interaction. (One still would have to decide on how to cancel / restart the process, either by having an explicit “Cancel” button or by restarting the process if users click a beverage button when they already have made choices for sugar / milk and cancelling it when no input is made for a certain time.)

In any case, I would keep the display to be able to present additional messages (“Product not available, please select other beverage”, “No milk today”, …)

I think our thoughts demonstrate that even seemingly “simple” and “straightforward” devices benefit from investing some effort in user interface design.

Mark said...

Thank you very much. It is motivating to receive feedback and to learn that people are getting something from my writings here.