Key Findings
The speech production and perception experiments confirmed that linguistic information in intonation is signalled, perceived, and processed in a systematically different way from paralinguistic information, as hypothesised by Autosegmental-Metrical theory:
multiple phonetic parameters covary in different ways to communicate different intonational meanings (pitch, duration, loudness, tempo, voice quality and spectral properties)
2) this is true for different types of categorical intonational information: 'grammatical' meaning (e.g. statement, question, or listing; phrasing; Post 2011a, 2011b, Delais-Roussarie et al. 2011, Hudson et al. 2010, Post et al. in preparation a.), as well as discourse meaning (e.g. new topic versus topic continuation; Zellers et al. 2009, 2010, Zellers and Post 2010, 2012)
3) the listener immediately perceives and exploits these multiple cues in the incoming signal in online interpretation (Zellers and Post 2010, Post et al. in preparation a.)
4) linguistic meaning is perceived significantly more categorically than paralinguistic meaning, even when the same cues are present in the signal (Post et al. 2013, in preparation a.).
The neuroimaging results also show differential processing for categorical linguistic and gradient paralinguistic meaning in intonation (Post et al. 2009, 2010, 2011, 2012a, 2012b, 2013, in prep. b; Bohr et al. in under revision):
5) distinct, but overlapping neural systems are engaged depending on type of meaning (i.e. linguistic or paralinguistic), irrespective of the acoustic cues that are present in the signal (i.e. whether they are held constant or systematically varied)
6) the subsystems which are engaged in the linguistic interpretation of intonational information are the same as those which support abstraction and categorisation for other types of categorical linguistic information in the speech signal (e.g. consonants and vowels); dissociations in lower-level auditory and higher-level linguistic subprocesses reflect distinctions made in current intonational theory.
These findings confirm that intonation is not merely a side effect of biological imperatives related to animal communication (cf. Biological Codes explaining correlations between pitch cues and speaker attitudes/feelings), but that it is properly part of the linguistic system (cf. grammaticalisation of cues for linguistically structured meaning; Gussenhoven 2004).
The key implication is that any formal linguistic model of intonation needs to distinguish between categorical linguistic and gradient paralinguistic meaning, while accommodating the complexities of the mapping relations between cues, meanings and various types of linguistic structures in the language.
Thus, this project has done much to reinforce the theoretical construct of a separation between phonetics and phonology in prosody, supporting the central tenet that underlies almost all current linguistic research in the area; to date, decisive evidence had been elusive.
A second implication is that hierarchically organised neural processing is a universal characteristic of speech processing, which encompasses both segmental and suprasegmental properties, and in which dissociations in lower-level auditory and higher-level linguistic subprocesses reflect distinctions made in current intonational theory.
We propose that intonation should be considered to be an integral part of a complex, dynamic language system whose outputs can be fully formalised with reference to its various linguistic components, and the mappings between them (Post 2011a, 2011b, Delais-Roussarie et al. 2011, Post et al. 2012, Zellers and Post 2012).