Bias is an outcome of human thought and often based on rules of thumb. Cognitive biases are instances of evolved mental behavior. Some are presumably adaptive, for example, because they lead to more effective actions in given contexts or enable faster decisions when faster decisions are of greater value. Others presumably result from a lack of appropriate mental mechanisms, or from the misapplication of a mechanism that is adaptive under different circumstances.

Though cognitive bias falls under the realm of Psychology, cognitive bias plays a vital role in user research. Understanding the various forms of cognitive biases will help a usability analyst when performing contextual inquiries and user interviews.

Wikipedia lists all the cognitive biases that makes for an interesting read. The list of biases allows a researcher understand the context behind user’s approach to tasks. For example, understanding the Hawthorne Effect – which is about the tendency to perform or perceive differently when one knows they are being observed – will help during a contextual inquiry. An understanding of the Planning Fallacy effect is useful in calculating the task completion times.

Initially I went about my tasks understanding AS/400 screens and ensuring they were recreated in the web application. Everything was fine on paper and screen. Nothing struck me as untoward. Only when I went back to the AS/400 documentation, I realised that working with the command-line interface was easier than the graphical interface. It was then I recalled a term called “device switching”.

Device Switching happens when a user switches between using two input devices. mostly a mouse and a keyboard. Marlin C. Brown in his book, Human-Computer Interface Design Guidelines, talks about this mouse-keyboard switching.

8.10 Mouse-Keyboard Switching

Avoid frequent mouse-keyboard switches.

Avoid requiring users to make frequent changes form keyboard to mouse. In keyboard-intensive tasks, such as word processing, provide the necessary functions on the keyboard (for example, cursor control keys) to permit the user to perform the task from the keyboard. Frequent changes from keyboard to mouse and back interfere with the flow, and thus the efficiency, of keyboard tasks. The users must reorient their hands to the keyboard after each mouse use.

Mouse & Keyboard, via Flickr user: stopthegears

The AS/400 application has been in use for more than two decades and that users have become proficient in using the keyboard. The AS/400 application, being a data entry intensive application and by virtue of its longevity, had ensured that users have a mental model of screens built into their minds and they have memorised the key sequences to use and navigate through the system.

As a result, I went back to the application and ensured that that tabbing order was in the same sequence as that of the green screen. This took care of the issue of frequent device switching associated with graphical interfaces.

The lesson I learnt from this was to test screens and forms for device switching issues. The lower the number of switches that occur, the better the usability of that screen or form would be.