In this paper I propose an analysis of two changes in case assignment occurring in quirky (oblique) subjects in Icelandic. The first change substitutes dative case for accusative (Dative Sickness), while the second involves the tendency for “impersonal” constructions to become personal, whereby oblique NPs occurring with the finite verb in 3rd person become nominative agreeing with the verb (Nominative Sickness). I argue that these two changes are conditioned by different factors.
Dative Sickness is motivated by semantics (thematic roles), while Nominative Sickness is motivated by syntax (structure). I suggest that both changes can be accounted for in terms of a cue-base approach to language acquisition.