Messaging Contrast in Interface Design
The man pushing the button to open the elevator door and cursing that the doors didn’t close shrugged it off to being Monday morning. The truth is, that I have done the same thing in the same elevator. The icons under the buttons are the little triangles pointing in for close and out for open.
When you’re in a rush, or not thinking about it, the icons look essentially the same. There isn’t enough contrast in the design and position of the buttons. If, besides the icons, the elevator company had place the words “open” and “close” under the buttons - the problem might be solved.
Yesterday I was going into a store when I was stopped in my tracks. On the glass doors were two red circles with the words “enter” on them. Sorry, I’m used to red circles meaning “do not enter”. If the circles had been green (or any other color than red), it would not have had that effect on me.
In building user interfaces for financial services, I know that red always means loss or warning. It’s one of the few tried and true rules. If you list a customer’s balances in red - they are going to be very uncomfortable.
When we speak of contrast in design, we are normally speaking about something like the difference between the levels of luminance in the figure and ground. Here I am talking about what I have termed messaging contrast.
Messaging contrast is the difference in presentation between messages that signify different instructions. Differences can include placement, size, color, luminosity, animation, etc.
This becomes especially important when talking about controls. The eject lever in fighter aircraft is placed apart from other controls, and marked in bright yellow and black stripes. Imagine if it was hidden amongst other controls and looked similar. The safety button on escalators is the only visible control and it’s usually in bright red under a plastic-hinged panel.
Messaging contrast reduces the amount of time a user needs to find and use a control, and makes it cognitively more efficient. A good rule of thumb is - the more a user has to think about using your “stuff” the less usable it is.
