Stupid Catalogue Tricks

[Updated to fix link to 'principle of least astonishment']

Like most catalogues, our system provides a basic keyword search box, as well as an "advanced keyword" search form that allows the user to set various options and search limits (sort order and date limits are the two obvious ones). The problem with our system (I don't know if this is a general "Innovative" issue, or just limited to the way MPOW has the catalogue configured) is that it doesn't do what the user expects. Consider this scenario:

• The user goes to the "advanced keyword search" screen, types in some search terms, changes the sort order to "relevance", and limits the results to "books"
• After looking at the search results, the user uses the keyword search box on the results screen to adjust the search terms and reruns the search
• The second set of search results is sorted by title (the default), and is no longer limited to just books.

This is a bit surprising to most users, and it's even been known to catch library staff out. If the user had, instead of just typing into the obvious, and very convenient, search box on the result screen, pressed the "Modify Search" button and returned to the advanced search form, then there would have been no problem. But who does that?

Library catalogues seem to regularly violate the principle of least astonishment in ways that would probably be easy to avoid. Why is that?