Cognitive and communicative function: The effects of chronological age and “handicap age”

Three classes of cognitive tests (short-term memory, long-term memory access/recall, and verbal ability) and one class of communicative tests (visual speech-reading) were administered to 49 hearing-impaired and 69 normal hearing subjects, varying in age between 23 and 75 years. It was found that when dB-loss and “handicap age” were partialled out, the negative effects of cognitive ageing remained: Speed in accessing alphanumeric symbols from long-term memory and as rehearsal speed correlated substantially with chronological age. Discriminant analyses revealed a communality between the discrimination of old from young subjects, and skilled from less skilled speech-readers: Visual decoding skill and rehearsal speed constituted the common discriminators. Departing from this result, an age-dependent componential model of visual speech-reading is delineated. with particular reference to the assumption that a temporally early lexical access system is crucial to the decoding of lip movements.