The lecture on design principles made me think of my experiences working in retail and the issues with user interfaces. I have witnessed countless customers struggle with eftpos devices. Some of the issues seem related to organization, with users struggling to find the right button to press while others relate to affordances, with users making the wrong assumption about what button they need to press. There is also feedback, often after a user pushes a button they are unable to distinguish the sound for a mistake from the sound for a correct entry and they will continue to enter information at the wrong time. Another feedback issue is response times, the loading between screens throws off customers and they begin to enter their information before the screen is ready.
I think Gestalt principles could also be applied to eftpos devices for a better screen layout. Buttons with different functions are too uniform and need to be grouped separately and with a different appearances. Perhaps a structure like the example with the coffee machine in the lecture could be beneficial, with buttons arranged in a way that mirrors the steps of the entry process.
In The Essential Guide to User Interface Design Galitz enforces the need for systems to respond in time with the user: “System responsiveness should match the speed and flow of human thought processes” also advising that “constant delays are preferable to variable delays” which highlights the timing issue of the eftpos device, the loading between screens varied, sometimes they were instantly responsive and other times they stopped to load. Customers who expected a quick transition pressed buttons before they realised the system was loading. Perhaps a forced delay would create a more consistent and less error-prone means of use from the customer.
The eftpos device also fails in “Visibility of system status” under Jakob Neilsen’s Usabilty Heuristics, with text and instructions far too small to read for many users with poor eyesight who sometimes try to guess what information they need to enter.
Galitz, Wilbert O. The Essential Guide to User Interface Design: An Introduction to GUI Design Principles and Techniques John Wiley & Sons 2007