The aim of the investigation was to develop indicators of changes in emotional states based on the speech process itself. Previous research had suggested that respiratory behaviour in speech might be a fruitful line to study. A simple method of recording breath intake from sound recordings was discovered. Two measures were derived from speech-breathing activity: the rate of respiration during speech and the output of speech (number of syllables) per expiration. Both of them proved to be highly reliable and sensitive, but the output of speech per expiration was the more constant, as well as more sensitive, of the two. The phonetic and physiological facts of speech production and psychological evidence and theories, in respect of respiratory behaviour, suggested interpretations of the psychological significance of these measures which are in the process of being tested. (Author's summary.)