Syllabic processing in visual word recognition in Alzheimer patients, elderly people, and young adults

Abstract

Background: Over the last decade Carreiras and colleages have assembled compelling empirical evidence that the syllable plays an important role in the visual recognition of polysyllabic words in Spanish. One of the clearest demonstrations of this is the syllable frequency effect: Words with high‐frequency syllables are responded to more slowly than words with low‐frequency syllables. Another key finding is the syllable congruency effect that has been obtained using the masked priming technique: Word recognition is facilitated by primes that correspond to the first syllable, relative to primes that contain one letter more or less than the first syllable. Aims: The study aimed to investigate the syllable frequency effect and the syllable congruency effect in Alzheimer patients, elderly people, and young adults. The goal was to examine whether and to what extent syllabic processing is preserved or deteriorates with age and/or this disease. If structural components of language are to some extent preserved in Alzheimer's disease (AD) patients and in elderly people, they should show the syllable congruency effect. If AD patients and elderly people have a breakdown in the ability to inhibit partially activated information, the syllable frequency effect may well turn out to be different in these two groups as compared to the young adults. Methods & Procedures: Two experiments, one investigating the syllable frequency effect and the other the syllable congruency effect, were carried out with Alzheimer patients, elderly people, and young adults. In Experiment 1 we used the same materials and procedure used by Carreiras and Perea (2002) in their Experiment 4. In Experiment 2 we created new materials manipulating syllable frequency (high and low) and word frequency (high and low). AD patients, elderly people, and young controls participated in the two experiments. Outcomes & Results: The results showed syllable congruency effects, replicating previous findings. However, syllable frequency effects were different for the three groups. Predictably, young adults responded more slowly to words with high‐frequency syllables than to words with low‐frequency syllables. In contrast, Alzheimer patients and elderly people responded more slowly to words with low‐frequency syllables than to words with high frequency syllables. Conclusions: In the context of activation models that take into account a syllabic level of representation, the present results suggest that the syllabic layer is preserved but the inhibitory process of competition between lexical candidates is impaired in Alzheimer patients and in elderly people. The research reported in this article has been partially supported by Grants SEJ2004‐07680‐C02‐02/PSIC and SEJ2006‐09238/PSIC from the Spanish Ministry of Education to MC and from the Spanish Agency of International cooperation (AECI ) and Fundación Carolina to SB. We wish to thank Humberto Arboleda and Rodrigo Pardo of the Grupo de Neurociencias de la Universidad Nacional de Colombia for providing us with information about the patients’ diagnosis profile and for kindly allowing us access to the patients.