Conceptual memory is a continuum between perceptions and abstractions. How does the brain remember objects such as a hammer and concepts such as "tool"? Well, it first learns basic features of encountered stimuli, such as the wood grains and metal curves of a hammer, and then organizes those features into progressively higher levels of abstraction.
Developers are expected to maintain expertise in their craft throughout their careers. Unfortunately, the path to becoming an expert is not easily walked: For a novice, evidence suggests this can be a 10-year journey. Furthermore, for experts trying to become experts in new domains, like the desktop developer becoming a web developer, there are many concepts that must be put aside and new ones learned.
Studies examining the difference between an expert and novice find that performance differences arise from differences in brain activity. Not only do experts require less brain activity than novices, they also use different parts of their brains: Experts use conceptual memory whereas novices use attentive memory. That is, experts are able to exploit abstractions in conceptual memory, whereas novices must hold primitive representations in attentive memory.
Sketchlet (alpha) is a software tool designed to help a programmer form and prime concepts by supporting abstraction and reviewing concepts that need to be refreshed. You can try it for yourself at sketchlet.sourceforge.net.
By expanding the programming environment to tablets, sketchlets on a "Code Pad" can provide extra mental space to build and remember concepts about code.
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A diary study of task switching and interruptions (Czerwinski)
Resumption strategies for interrupted programming tasks (Parnin, Rugaber)