Bradyphrenia and bradykinesia both contribute to altered speech in schizophrenia: a quantitative acoustic study

To evaluate the relative contributions of motor and cognitive symptoms on speech output in persons with schizophrenia (SZ).

Studies of speech production in SZ suggest that atypical prosody (eg, pause) is related to clinical symptoms manifest in flat affect and alogia. Others have suggested that a more general motor slowing, bradykinesia, leads to measurable speech changes.

Thirteen participants with SZ and age-matched control subjects were included for between-group and by-task comparisons. Two levels of task complexity were analyzed acoustically to determine distinct and overlapping features of speech pause.

For the free-speech task, group differences were found on measures of average pause duration, pause variability, percent pause, and cumulative pause time. Conversely, for the rote-speech task, group differences were found only on measures of average pause duration and pause variability.

In persons with SZ, differences in the average and variability of pause duration may be reflected in speech motor slowing, whereas more global measures (eg, percentage pause) may better reflect a paucity of thought and idea generation related to the cognitive-linguistic aspects of free speech. These findings corroborate and extend the paucity of thought hypothesis in SZ to include an influence of motor slowing on speech production.