Several previous studies have shown that memory span is greater for short words than for long words. This effect is claimed to occur even when the short and long words are matched for the number of syllables and phonemes and so to provide evidence for subvocal articulation as being one mechanism that underlies memory span (Baddeley, Thomson, & Buchanan, 1975). The three experiments reported in this paper further investigate the articulatory determinants of word length effects on span tasks. Experiment 1 replicated Baddeley et al.'s finding of an effect of word length on auditory and visual span when the stimuli consist of words that differ in terms of the number of syllables. Experiments 2 and 3 showed that the effects of word length are eliminated when the words in the span task are matched for the number of syllables and phonemes but differ with respect to the duration and/or complexity of their articulatory gestures. These results indicate that it is the phonological structure of a word and not features of its actual articulation that determines the magnitude of the word length effect in span tasks.

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In the early stages of neurodegenerative disorders, individuals may exhibit a decline in language abilities that is difficult to quantify with standardized tests. Careful analysis of connected speech can provide valuable information about a patient's language capacities. To date, this type of analysis has been limited by its time-consuming nature. In this study, we present a method for evaluating and classifying connected speech in primary progressive aphasia using computational techniques. Syntactic and semantic features were automatically extracted from transcriptions of narrative speech for three groups: semantic dementia (SD), progressive nonfluent aphasia (PNFA), and healthy controls. Features that varied significantly between the groups were used to train machine learning classifiers, which were then tested on held-out data. We achieved accuracies well above baseline on the three binary classification tasks. An analysis of the influential features showed that in contrast with controls, both patient groups tended to use words which were higher in frequency (especially nouns for SD, and verbs for PNFA). The SD patients also tended to use words (especially nouns) that were higher in familiarity, and they produced fewer nouns, but more demonstratives and adverbs, than controls. The speech of the PNFA group tended to be slower and incorporate shorter words than controls. The patient groups were distinguished from each other by the SD patients' relatively increased use of words which are high in frequency and/or familiarity.