Age-related decline in sentence processing: Deriving corpus-linguistic hypotheses from psycholinguistic data

Abstract

Healthy aging is associated with language changes. We here advocate the position that a strong determinant of such changes may be alterations in the underlying processing systems. Age-related processing differences of language information such as syntactic structure or semantic content might entail changes observed in corpus research. That is specifically because information on, for example, syntactic structure and semantic content can facilitate language processing (Bonhage et al. 2014) and thereby determine language use as observed in corpora. It has previously been suggested that older adults’ syntactic but not semantic information processing may be compromised (Radvansky & Dijkstra 2007). Therefore, our research has examined whether the abilities to process syntactic structure and semantic content undergo differential changes during healthy aging. We expected a decreased benefit of information on syntactic structure but an enhanced benefit of semantic content on language processing in older compared to younger adults. To this end, in an experimental setting, we manipulated the availability of syntactic structure and semantic content (Table 1). That is, syntactic information was only available in sentences but not in word lists whereas semantic content was only available in real word sentences or real word lists but not in pseudoword sentences or pseudoword lists. Participants had to remember sentences or lists for a subsequent comprehension task. In total, 53 healthy, younger (mean age: 26 years; SD: 3 years) and 53 healthy, older adults (mean age: 65 years; SD: 3 years) participated in this study. No participant suffered from any neurological disorders according to self-report. The age groups were matched upon their level of education (i.e., minimum of 13 years). We assessed whether the availability of syntactic structure or semantic content would differentially facilitate younger compared to older adults’ language comprehension. The results showed that the availability of syntactic structure was less beneficial for older than younger adults. In contrast, the benefit of semantic content was comparable across age groups. In sum, this means that healthy aging compromises the processing of syntactic structure, but spares the processing of semantic content. Our findings may thus suggest that semantic information processing may become relatively more important for successful language processing with advancing adult age, possibly inducing a syntactic-to-semantic-processing strategy shift. These clear-cut psycholinguistic changes in language processing generate strong hypotheses for corpus- linguistic research: Older adults’ disadvantage in the processing of syntactic information may decrease the complexity of their sentence production, while semantic processing and production remain unchanged. We propose to test these hypotheses by an interdisciplinary approach combining methodology from natural language processing and psycholinguistics