Pitching an Argument: Intonation, information, and inference in syllogistic discourse
Hughson, Stuart Ian
In the century or so that syllogisms have received the attention of psychologists, their interpretation both as and within particular types of discourse has been largely downplayed. A significant element in the guidance of interpretation is information structure as expressed in prosody. This thesis explores the role of intonation in syllogistic discourse and its effect on reasoning. A theoretical analysis of the information structures of syllogisms is presented which produces two classes of intonation patterns, the 'contextually concordant' (CC) and the 'contextually neutral' (CN), putatively corresponding to two discourse types. These are then investigated in a series of experiments. The initial observational study aims at confirming the use and significance of CC and CN patterns in a syllogism solving task. The remaining two experiments employ a purpose-built voice synthesiser to investigate the effects of imposing CC and CN contours on premises, first in a syllogism solving task and then in a syllogism evaluation task. The results show that both CC and CN intonation patterns are indeed used by participants and bear a systematic relationship to both the number and accuracy of conclusions they draw. When used in the presentation of syllogisms, however, these patterns do not influence the production of conclusions, only the evaluation of them. It is therefore argued that the discourse types to which they relate depend upon whether the syllogism is interpreted as a proof or as a problem. Further work based on these findings could aim to probe the informational links between conclusions and premises and thereby elucidate the coherence of arguments.