Semantic complexity and rehabilitation of language deficits

The semantic complexity hypothesis:

Read about our work in the Scientific American.

Our laboratory has been instrumental  in extending the CATE hypothesis developed by Thompson and colleagues to the lexical retrieval and word production domain by showing that training atypical examples within a semantic category results in greater generalization to untrained typical examples than vice versa (Kiran, 2007, 2008; Kiran & Bassetto, 2008; Kiran & Johnson, 2008). In the first study, Kiran and Thompson (2003) sought to determine the effect of typicality of category exemplars within the categories of birds and vegetables on naming in four aphasic patients with anomia. The authors found that patients who were trained on naming of atypical exemplars demonstrated generalization to naming of typical items whereas individuals given therapy with typical exemplars did not show generalization to atypical items. In another study Kiran, (2008), the effect of typicality was examined in the context of two inanimate categories (clothing, furniture). Four of the five participants trained on atypical items demonstrated significant generalization to untrained items in a category and training typical examples did not result in generalization to untrained atypical examples within a category. Three other participants were involved in a typicality treatment study examining well-defined categories Kiran and Johson (2008). Well-defined categories (shapes, odd numbers) have rigid category boundaries and an all or none membership of corresponding category exemplars, but are psychologically processed in part as having a prototypicality structure (Amstrong et al, 1983). Results revealed two of the three participants trained with atypical items improved in naming both trained atypical and untrained typical items in the category whereas training typical examples did not improve naming of atypical examples.

The applicability of complexity (Kiran, 2007) extends into domains other than categories of concrete objects. Similar findings were observed during treatment of lexical retrieval of abstract or concrete words by utilizing abstractness as a marker of complexity (e.g., prayer, solace, candle within the context of church). Three of four patients with aphasia showed improvement on trained abstract words (e.g., prayer, within the context of church) and generalization to untrained concrete words (e.g., candle within the context of church). Two of the four patients showed improvement on trained concrete words, but no generalization was observed to untrained abstract words Kiran, Sandberg & Abbott 2009.