Why reference to the past is difficult for agrammatic speakers

Abstract

Many studies have shown that verb inflections are difficult to produce for agrammatic aphasic speakers: they are frequently omitted and substituted. The present article gives an overview of our search to understanding why this is the case. The hypothesis is that grammatical morphology referring to the past is selectively impaired in agrammatic aphasia. That is, verb inflections for past tense and perfect aspect are hard to produce. Furthermore, verb clusters that refer to the past will be affected as well, even if the auxiliary is in present tense, as in he has been writing a letter. It will be argued that all these verb forms referring to the past require discourse linking [Zagona, K. (2003). Tense and anaphora: Is there a tense-specific theory of coreference. In A. Barrs (Ed.), Anaphora: A reference guide (pp. 140–171). Oxford: Blackwell Publishing] and discourse linking is affected in agrammatic aphasia [Avrutin, S. (2006). Weak syntax. In K. Amunts, & Y. Grodzinsky (Eds.), Broca's region (pp. 49–62). New York: Oxford Press]. This hypothesis has been coined the PAst DIscourse LInking Hypothesis (PADILIH) [Bastiaanse, R., Bamyaci, E., Hsu, C.-J., Lee, J., Yarbay Duman, T., & Thompson, C.K. (2011). Time reference in agrammatic aphasia: A cross-linguistic study. Journal of Neurolinguistics, 24, 652–673]. The PADILIH has been tested in several languages and populations that have hardly been studied before in aphasiology: languages such as Turkish, Swahili and Indonesian were included, as well as monolingual and bilingual populations. In all these populations, the same test has been used: the Test for Assessing Reference of Time [Bastiaanse, R., Jonkers, R., & Thompson, C.K. (2008). Test for assessing reference of time (TART). Groningen: University of Groningen] to enable reliable comparisons between the languages. The results show that the PADILIH predicts the performance of agrammatic speakers very well: discourse-linked grammatical morphemes expressing time reference to the past are hard to produce for agrammatic speakers, whereas non-discourse-linked verb inflections (for present and future) are relatively spared. In languages that use aspectual adverbs (free-standing and optional time reference markers), such as Chinese and Indonesian, time reference to all time frames is impaired, since all aspectual adverbs, regardless of the time frame they refer to, require discourse linking. Remarkably, the problems are not restricted to grammatical morphemes: the production of temporal lexical adverbs is impaired as well.

Keywords:

• agrammatic aphasia
• time reference
• PADILIH
• tense
• aspect

Acknowledgments

I thank all my co-workers in the TART-project. They made the translations and adaptations of the tool, tested all the non-brain-damaged and aphasic individuals and analyzed the results. Also, they wrote the original papers. Without them it would not have been possible to run this project. I am also grateful to Katrina Gaffney and Ron van Zonneveld for their comments on an earlier version of this paper.

Declaration of Interest: The author reports no conflict of interest.

Notes

1 Some non-brain-damaged speakers did score below 90% correct on the Indonesian TART, which was slightly adapted to the idiosyncratic time reference features of the language. However, also in Indonesian, the agrammatic speakers performed significantly worse than the non-brain-damaged speakers.

2 Some languages, such as English, have regular and irregular verb inflections or have several verb declinations. Since we used the same verbs in all languages, it was impossible to match the items on regularity. For these languages, it was analyzed post hoc whether these variables played a role. That was nowhere the case.

3 The difference between the two forms that refer to the past is also significant. Since this is not essential to the current paper, this finding is further ignored.