Reaction times of normal and subnormal subjects were compared, when a warning stimulus varied in modality as well as in its temporal relation to the RT signal. When the warning stimulus was in a different modality from the RT signal, reaction times were shorter than when both were in the same modality. Mongols, in contrast to the other subjects, responded relatively faster to light than to sound.
The effect of varying the time interval between warning and signal was linearly related to response speed. The results are discussed in respect to the comparative alerting effects of temporal relations between stimuli and their different modalities.
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