Location overloading

Raskin defines an interface as modal for a gesture when the current state is not the user’s locus of attention and the interface gives one of several responses depending on that state (Raskin 2000, ch. 3). A sidebar item whose target depends on an out-of-view scope filter fits that definition. Tesler spent his career removing modes from text editing (Tesler 2012). Norman’s taxonomy of action slips puts mode errors under errors in forming the intention: the user’s action is right for one state and the system is in another (Norman 1981).

Expert users stop reading labels and go by place. Scarr, Cockburn, Gutwin and Bunt showed that a flat, spatially stable command layout (CommandMaps) beats menus and the Ribbon for experienced users (Scarr et al. 2012). Scarr, Cockburn, Gutwin and Malacria found spatial-memory gains survive translation and scaling of a layout but are hurt when it reflows (Scarr et al. 2013). Robertson et al.'s Data Mountain showed people retrieve documents better when they place them in space themselves (Robertson et al. 1998). Cockburn, Gutwin and Greenberg model the shift from visual search to decision by location as users learn a stable menu (Cockburn et al. 2007). Overloading keeps the place stable but changes the meaning, so the memory still fires and lands on the wrong thing.

Findlater and McGrenere found a static split menu significantly faster than an adaptive one, and most users preferred the adaptable (user-controlled) version (Findlater & McGrenere 2004). Gajos et al. map when adaptation helps and when it hurts; predictability is a large part of the answer (Gajos et al. 2006).

Nielsen’s heuristics #4 (Consistency and standards: users should not wonder whether different situations or actions mean the same thing) and #6 (Recognition rather than recall: users should not have to remember information from one part of the interface to another) both apply (Nielsen 1994/2024). Norman separates affordances (what you can do) from signifiers (what tells you how and where) (Norman 2013). An overloaded slot has one signifier for two affordances.

Cognitive load theory holds that working memory is limited and that load spent on things other than the task gets in the way of learning (Sweller 1988). Tracking a hidden scope is that kind of load.

Fitts’s law ties pointing time to target distance and size (Fitts 1954). Practiced users aim before they look; a stable target keeps that aim valid, an overloaded one makes the aim land on a different function.