It is a well-known fact of cognitive science that human short-term memory (SM), when compared to other attributes of our memory systems, is exceedingly limited. This fact has been the focus of thousands of studies over the last 50 years. Scientists have poked and prodded this aspect of human cognition to determine exactly how SM operates and what impacts SM effectiveness. As we go about our daily lives, short-term memory makes it possible for you to engage with all manner of technology and the environment in general.
SM is a temporary memory that allows us to remember a very limited number of discrete items, behaviors, or patterns for a short period of time. SM makes it possible for you to operate without constant referral to long-term memory, a much more complex and time-consuming process. This is critical because SM is fast and easily configured, which allows one to adapt instantly to situations that might otherwise be fatal if one were required to access long-term memory. In computer-speak, human short-term memory is also highly volatile. This means it can be erased instantly, or more importantly, it can be overwritten by other information coming into the human perceptual system.
Where things get interesting is the point where poor user interface design impacts the demand placed on SM. For example, a user interface design solution that requires the user to view information on one screen, store it in short-term memory, and then reenter that same information in a data field on another screen seems like a trivial task. Research shows that it is difficult to do accurately, especially if some other form of stimulus flows between the memorization of the data from the first screen and before the user enters the data in the second.
This disruptive data flow can be in almost any form, but as a general rule, anything that is engaging, such as conversation, noise, motion, or worst of all, a combination of all three, is likely to totally erase SM. When you encounter this type of data flow before you complete transfer of data using short-term memory, chances are very good that when you go back to retrieve important information from short-term memory, it is gone!
One would logically assume that any aspect of user interface design that taxes short-term memory is a really bad idea. As was the case with response time, a more refined view leads to surprising insights into how one can use the degradation of short-term memory to actually improve game play engagement. Angry Birds is a surprisingly smart manager of the player’s short-term memory.
By simple manipulation of the user interface, Angry Birds designers created significant short-term memory loss, which in turn increases game play complexity but in a way that is not perceived by the player as negative and adds to the addictive nature of the game itself. The subtle, yet powerful concept employed in Angry Birds is to bend short-term memory but not to actually break it. If you do break SM, make sure you give the user a very simple, fast way to accurately reload.