Purpose: Of the three currently recognized variants of primary progressive aphasia, behavioral differentiation between the nonfluent/agrammatic (nfvPPA) and logopenic (lvPPA) variants is particularly difficult. The challenge includes uncertainty regarding diagnosis of apraxia of speech, which is subsumed within criteria for variant classification.…

Two studies examined children's perceptual biases in extracting or identifying words from the stream of speech. In one study, evidence for the salience of stressed and final syllables was found. Young children less frequently omitted those syllables from their productions and produced unstressed and nonfinal syllables less accurately. A second…

The ontogenetic development of human vocal utterances and their role in early interaction processes were studied with a three-month-old baby. Recordings were made of infant vocalizations in the home and the sounds were classified. During a five-minute segment between the mother and infant, the infant produced 59 utterances, 93 percent of which had…

Infants parse speech into word-sized units according to biases that develop in the first year. One bias, present before the age of 7 months, is to cluster syllables that tend to co-occur. The present computational research demonstrates that this statistical clustering bias could lead to the extraction of speech sequences that are actual words,…