The purpose of current study was tocompare the narrative and persuasive discourses of four groups of healthyadults in order to test the age-related changes of macrostrutural (cohesion)and macrolinguistic level (coherence) measuresusing a narrative discourse and persuasive discourse task. The analysis of dataindicated that aging had an impact on the reduction of the macrolinguisticlevel in both type of examined discourse but dose selective effect onmacrostructural level according to type of discourse.The measure ofcohesion deal with how a participant connect his/her utterances and ideas, bymeans of different kinds of cohesive ties in the surface structure ofdiscourse, for a listener to follow. In this study, participants with agingpresents narrative discourses with significantly fewer cohesive ties per C-unitcompared to other age groups.
This result may suggest that the group with aginghad difficulties to – conceptually and linguistically- link their utterances innarrative discourse but this is not the case in persuasive discourse. The typeof discourse task has been cited among the factors that hasan influence on the individual’s performance (Ghayoumi,Yadegari et al. 2015) and this result is likely due to the fact that,contrary to persuasive discourse task, narrative discourse using picturesequences facilitate the organization of the story structure by visuallyproviding the temporal and logical sequence of events that make theestablishment of cohesion easier in stories from picture sequences (Marini, Boewe et al.
2005, Cannizzaro and Coelho2013). But aging people cannot exploit these structuring aids thatfacilitate formation of discourse as much as other participant group.In Glosser andDesser’s study, no difference was found in the use of cohesive ties in thenarrative discourses (Glosser and Deser 1992).Notable point is that the narrations was elicited by an informal interview intheir study but in current study, a sequential picture elicit the narrativediscourse. Coherence isdefined as relationships between the meanings underlying the surface structureof a discourse. It refers to a cognitive representation that reflects theinteraction between linguistic/discourse characteristics and world knowledge (Van Dijk 2011).
On the other hand, Impairmentsin a number of cognitive tasks (working and long-term memory) are seen as partof the normal ageing process in humans (Connor2001). It has been proposed that executive functions may be an importantcontributor to discourse generation (Douglas2010). Accordingly, it is expected that this supra-sentential level ofdiscourse is affected by aging. The findings ofpresent study based on the decreased discourse ability average cohesion andcoherence during aging are in line with (Northet al. 1986, Glosser and Deser 1992, Schneider et al.
2000, Capilouto, Wrightet al. 2005, Juncos-Rabadán et al. 2005, Marini, Boewe et al. 2005)indicating declined discourse performance with age.AlthoughMackenzie showed that the educational level does not affect the narrativediscourse of individuals with primary and higher education (Mackenzie 1999), because of the heterogeneityin the educational level of different age groups in this study, the resultsshould be interpreted with caution. Additionally, as sample size of the studyis low, the generalization of findings should be made with more caution.