Disruption of the serial position effect as an early marker of Alzheimer's disease in Spanish-English bilinguals.

OBJECTIVES: The present study examined if disruption of serial position effects in list recall could serve as an early marker of Alzheimer's disease (AD) in Spanish-English bilinguals. METHODS: We tested 20 participants initially diagnosed as cognitively normal or with mild cognitive impairment who declined and eventually received a diagnosis of AD (decliners), and 37 who remained cognitively stable (controls) over at least 2 years. Participants were tested on the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning Test in English or Spanish as part of an annual neuropsychological evaluation. RESULTS: Compared to controls, decliners exhibited significantly reduced recall including reduced primacy scores (i.e., items recalled from the first three list items on Trial 1), whereas recency scores (i.e., items recalled from the last 3 list items on Trial 1) were equivalent in decliners and controls. Further analyses suggested that the sensitivity of the primacy effect to preclinical AD was initially stronger in participants tested in Spanish, a surprising finding given that the CERAD was developed for English speakers. However, in the subsequent year of testing, primacy scores declined to the same level regardless of language of testing. CONCLUSIONS: Several list learning measures may facilitate early diagnosis of AD in Spanish-English bilinguals, possibly including the relatively understudied primacy effect. Additional studies are needed to investigate the possibility that linguistic or demographic variables might modulate sensitivity of list learning tests to preclinical AD, which could lead to broader improvements in their utility for early diagnosis of AD in all populations.

Order effects in bilingual recognition memory partially confirm predictions of the frequency-lag hypothesis.

The present study examined task order, language, and frequency effects on list memory to investigate how bilingualism affects recognition memory. In Experiment 1, 64 bilinguals completed a recognition memory task including intermixed high and medium frequency words in English and another list in Spanish. In Experiment 2, 64 bilinguals and 64 monolinguals studied lists with only high frequency English words and a separate list with only low frequency English words, in counterbalanced order followed by a recognition test. In Experiment 1, bilinguals who completed the task in the dominant language first outperformed bilinguals tested in the nondominant language first, and order effects were not stronger in the dominant language. In Experiment 2, participants who were tested with high frequency word lists first outperformed those tested with low frequency word lists first. Regardless of language and testing order, memory for English and high frequency words was lower than memory for Spanish and medium frequency (in Experiment 1) or low frequency (in Experiment 2) words. Order effects on recognition memory patterned differently from previously reported effects on picture naming in ways that do not suggest between language interference and instead invite an analogy between language dominance and frequency of use (i.e., dominant language = higher frequency) as the primary factor affecting bilingual recognition memory.