Informative Spatial cues
It should be noted that the frequency range of the sound affects both the presence and quality of both interaural time differences (ITD) and interaural intensity differences (IID), moreover, the intensity, duration, rise/fall time and complexity of the sound also affects the detecting of the sound. The lack of spatial cuing decreased the response time of subjects for they did not have basis for localization. Flanagan, McAnally, Martin, Meehan & Oldfield (1998) visual search times were reduced when spatially informative auditory information was supplied.
They used a spatial localization task in which the search for a visual target was aided by either a visual arrow or an auditory cue. They found both the visual and the auditory cues aided in significantly reducing the search times when compared to unaided search. It is however important that the visual and auditory information presented are detectable and localizable. Hence a signal should be localizable when information presented is critical (i. e. ; location of threats such as enemy fighters, missiles etc.) and that information presented is expected in that location will improve response time and accuracy (Posner, 1980, Spence and Driver, 1996).
One interesting observation from experiment 5 was the overall decrease of response times for all conditions. In comparison to experiment 3 overall response times were about 30ms faster in experiment 5. The question raised is could the replacement of the spatially informative pure tone with the spatially informative speech have caused this improvement in overall response time.
The introduction of speech alone did not have the effect of reducing response times in experiment 4 where a non-spatial speech cue was used. Hence the combination of the informative speech with the likely spatial location of the target may engage both exogenous and endogenous processes more completely than the just the likely spatial location alone. The essentially “double-barred” cue of both correct spatial location and the informativeness of a speech confirmation of the spatial location could have the effect of increasing the subject’s confidence and/or efficiency at completing the task correctly.
Therefore the reduced response times observed in experiment 5 in comparison to experiment 3 could be as a result of this “double-barreled” type of cue. Unfortunately, this assumption cannot be made in this case due to the fact that not all subjects who completed experiment 3 also completed experiment 5. Furthermore despite three subjects completing both experiments, the order of completion was the same with experiment 3 completed first, therefore no statistical analysis could be performed on the data due to the possibility of practice effects influencing the result.