Morphology
This study used an experimental approach to explore the morphological structure of so-called 'zero-derived' items in English -- words that can act as members of more than one lexical class without any formal change (e.g. to walk/a walk).
The first set of experiments aimed to discover evidence that, in the minds of native speakers, one item in such pairs is marked as being derived from the other.
The second set of experiments investigated the theory that some of these items are not in fact in a derivational relationship, but are instead two uses of a single root which is underspecified for lexical class.