Feast or famine: Fixed expressions in the spontaneous speech of left hemisphere- and right hemisphere-damaged subjects

The preservation of swearing, serial speech, and speech formulas is well-attested in clinical descriptions of aphasia. Survey studies have not only confirmed these observations; they have also documented the selective preservation of proper nouns in the residual speech of left hemisphere (LH) damaged subjects (Blanken, Wallesch, & Papagno, 1990; Code, 1982). It had not been resolved whether these preserved utterances are produced by the undamaged right hemisphere (RH), or by intact areas of the LH. Further insights have come from functional brain imaging and behavioral studies, which have suggested that unlike novel expressions (which are lateralized to the left hemisphere), serial speech (i.e., counting), fixed expressions (i.e., idioms), and proper nouns (names of known persons) may be represented in the both hemispheres (Kempler, Van Lancker, Marchman, & Bates, 1999; Ohnesorge & Van Lancker, 2001; Van Lancker, McIntosh, & Grafton, 2003). Relatively little is known about incidence of non-novel expressions in the spontaneous speech of normal or brain damaged subjects. Interest in this property of normal speech has recently arisen (e.g., Wray & Perkins, 2000). Counts derived from studies of conversation using a screenplay, compared to published accounts derived from natural speech corpora, suggest that between 15 and 40% of utterances are fixed expressions (Van Lancker-Sidtis & Rallon, 2004). The importance of fixed expressions in language use, combined with converging evidence of a role of the RH in processing non-novel language, led to this study. Our goal was to examine hypotheses about hemispheric processing of fixed expressions in the spontaneous speech of persons with unilateral brain damage, in comparison with age and education matched normal–control subjects.