I use the term “sociocognitive complexity” to describe patterns of embedment of mental states within mental states in fiction. Any given work of fiction can be viewed as a succession of scenes of varying sociocognitive complexity, including scenes in which the same character reflects upon her own mental states. (This is to say that sociocognitive complexity requires multiply embedded mental states but not necessarily multiple characters.)
Writers make some characters more “cognitively complex” than others, that is, capable of embedding more mental states. For instance, Fanny Price from Austen’s Mansfield Park is often preoccupied by what other people might be thinking about other people’s feelings, while Lady Bertram seems to be incapable of such complex mind-reading attributions. Approaching fiction in terms of its sociocognitive complexity is thus ultimately an historicist inquiry. We may ask what factors influence the writer’s decision about which characters will carry on complex mind-reading reflections and which will have to settle for simpler ones. Such decisions are often shaped by historically contingent genre conventions, by contemporary ideological preoccupations of the society, as well as by the personal history of the author.