IMPLICIT AND EXPLICIT USE OF SCRIPTED CONSTRAINTS IN LIPREADING

The interaction between typicality, abstraction and temporal order wit hin scripts, and different contextual conditions, was specified in a l ip-reading model of predictive sentence comprehension. The model sugge sts both an implicit and an explicit mode of script processing, emphas ising either hierarchical or temporal representations within scripts. In each of five experiments, subjects lip-read 48 sentences from three scripts. Different levels of abstraction (basic vs low-level), typica lity (typical vs atypical) and temporal order (early vs late) were alw ays embedded in each sentence. To assess a baseline, Experiment 1 meas ured ''pure'' lip-reading in the absence of scripted context. In Exper iment 2, the script header was present. Experiment 3 correctly or fals ely primed the script activation along each organisational dimension. In Experiment 4, the subjects received correct or false script-scene i nformation, either before or after sentence presentation. In Experimen t 5, the subjects received either basic or specific scene context befo re sentence presentation. The results confirmed the predictions in tha t: (a) there were minor dimensional effects when the script heading wa s absent; (b) typicality and abstraction constituted the main organise rs within scripts, and typical, basic-level information occurring late was always implicitly activated; (c) the temporal structure at atypic al, low levels of abstraction was the only dimension that was explicit ly activated (i.e. sensitive to false cueing); (d) pre-exposed correct script-scene context enhanced lipreading relative to the other condit ions; and (e) specific scene context optimises a vertical ''upwards'' activation for basic and typical representations. It was concluded tha t the predictive script model of lip-reading received strong support, and that a ''weak'' hierarchical view of scripts is compatible with im plicit processing, whereas a ''strong'' temporal view is compatible wi th explicit script processing.