My colleagues in Finland and I have published another paper on morphological processing in Finnish, a language with a highly complex morphological system. In this paper we look at how morphological and lexical processing differs for healthy older adults and people with Mild Cognitive Impairment or Alzheimer’s disease, compared to healthy younger adults. The paper is available here: https://doi.org/10.1016/j.cortex.2018.
Individuals with Alzheimer’s disease often show declines in semantics (a word’s meaning). It is unclear whether this semantic decline affects morphological processing. In order to answer this question, we tested to what degree word recognition in Finnish was influenced by semantic and form-based (spelling) factors and how the reliance on these factors changes with age and with neuropathology. In line with previous research on Alzheimer’s disease, we found decreased reliance on semantic aspects of word recognition for these patients. However, what was particularly interesting in this study was that healthy older adults and individuals with Mild Cognitive Impairment showed similar patterns to what was found for patients with Alzheimer’s. In other words, all three of the older adult groups showed greater reliance on form-based factors for word recognition than younger adults.
Reading a word activates morphologically related words in the mental lexicon. People with Alzheimer’s disease (AD) or Mild Cognitive Impairment (MCI) often have difficulty retrieving words, though the source of this problem is not well understood. To better understand the word recognition process in aging and in neurodegenerative disorders such as MCI and AD, we investigated the nature of the activation of morphologically related family members in 22 Finnish speakers with AD, 24 with MCI, and 17 cognitively healthy elderly. We presented Finnish monomorphemic (base form) nouns in a single-word lexical decision experiment to measure the speed of word recognition and its relation to morphological and lexical variables. Morphological variables included morphological family size (separate for compounds and derived words) and pseudo-morphological family size (including the set of words that have a partially overlapping form but that do not share an actual morpheme, e.g., pet and carpet, or corn and corner). Pseudo-morphological family size was included to examine the influence of words with orthographic (or phonological) overlap that are not semantically related to the target words. Our analyses revealed that younger and elderly controls and individuals with MCI or AD were influenced by true morphological overlap (overlapping forms that also share meaning), as well as by the word’s pseudo-morphological family. However, elderly controls and individuals with MCI or AD seemed to rely more on form overlap than young adults. This demonstrates that an increased reliance on form-based aspects of language processing in Alzheimer’s disease is not necessarily due to a partial loss of access to semantics, but might be explained in part by a common age-related change of processes in written word recognition.
My collaborators and I have a new paper out in Applied Psycholinguistics. This study examines word processing in Finnish speakers in order to explore questions about the factors that influence the speed of lexical recognition. Finnish provides a unique opportunity to investigate stem allomorphy, which is variation in word stems across different forms of the word, such as foot and feet in English. Finnish has rich stem allomorphy, with some words consisting of 3 or 4 stem allomorphs.
In a previous paper, Nikolaev et al. (2014) showed that words with higher stem allomorphy were recognized more quickly than words with lower stem allomorphy. However, there was a confound with allomorphy in that words with higher stem allomorphy tend to come from an unproductive inflectional class (in other words, new words are not created using those word forms) while words with lower stem allomorphy tend to come from a productive inflectional class. In the newly published study, we sought to disentangle the effects of stem allomorphy and inflectional productivity by including a third type of words which has low stem allomorphy but comes from an unproductive class.
The results replicated Nikolaev et al. (2014), showing that participants recognized words with higher stem allomorphy faster than words with lower stem allomorphy. Furthermore, we ruled out the potential contribution of productivity of inflectional class as a predictor of word recognition speed.
This study provided the basis for two follow-up studies. In the first, we compared healthy older adults and people with Mild Cognitive Impairment and Alzheimer’s dementia to determine whether the factors affecting word recognition (including stem allomorphy) change in pathological aging. This paper is currently under a second round of reviews at Cortex. The second study examines cortical structure in the same older adult groups and their relation to the processing of stem allomorphy differences. This paper is currently in preparation.
For a free PDF of the article, click here.
I am excited to have a book chapter with Loraine Obler and Dalia Cahana-Amitay on brain and language in aging in the newly published Handbook of Communication Disorders, edited by Amalia Bar-On and Dorit Ravid. The handbook offers a rich collection of papers on language acquisition and language decline, literacy, as well as the effects of socioeconomic status, multilingualism, and speech and hearing impairments on language learning and use, among many other interesting and relevant topics.
The journal Linguistic Approaches to Bilingualism has just published our article titled “Length of residence: Does it make a difference in older bilinguals?” as an Online-first article. http://doi.org/10.1075/lab.15001.hig
In this article we explore three factors that may affect second-language (L2) attainment: the length of time spent living in a country where the L2 is spoken, the age at which the L2 was first learned, and the age at which the person’s L2 skills are tested. The first two factors have often been studied in second language acquisition research, but the third variable (age at testing) is usually ignored. In this article we argue that there are important reasons to consider age a potentially important/influential factor given the research showing cognitive and language declines in older adults. We reviewed a set of studies that included length of residence as a potential factor in accounting for individual differences in L2 attainment. We divided the studies into those that included bilinguals who were all under the age of 55 and those that included some bilinguals over 55. Although there were only a small number of studies that included older adults, the findings suggest that when older adults are included in the sample, there is less chance that a positive effect of LOR on L2 attainment is found (in other words, longer LOR is not associated with better L2 performance). By contrast, studies that included only younger adults reported a positive effect of LOR more often than no effect of LOR. We suggest that detrimental effects of aging on language and cognition may be counteracting the positive effects of length of residence and that aging should not be overlooked as a potentially influential variable in studies of second language acquisition.
A pre-print version of the article can be found on my Research Gate profile here.
I’m delighted to announce that an article I worked on with members of the Language in the Aging Brain Lab at the Boston VA Hospital has just been published online! The article is titled “How older adults use cognition in sentence-final word recognition” and it is published in the journal Aging, Neuropsychology, and Cognition.
The study looked at how individual differences in executive control and working memory affected older adults’ ability to understand words at the end of sentences. The words varied in their degree of predictability and in the degree of noise they were placed in. The main finding was that better inhibitory control led to better word recognition.
Would you like to read a copy of the article? The first 50 people who use this link will get a free copy: http://www.tandfonline.com/eprint/9uMGCVIzHFznG8fTR5xp/full. Or you are welcome to email me at firstname.lastname@example.org.