THE PERCEPTION OF LIGHT SIGNALS: THE EFFECT OF THE NUMBER OF IRRELEVANT LIGHTS

The experiment described was carried out to find the effect of the number of irrelevant lights on the human response time to light signals appearing amongst thorn. Both the signal lights and the irrelevant lights could be made steady or flashing: this produced four conditions of coding of the signal lights from the background, e.g. Hashing signal with steady background and so on. It was found that the geometric moan response-time increased to an unusually large extent, from 0·8 sec with no background lights up to nearly 2 sec with 21. A background of flashing lights was found to increase the response-time more than a background of steady lights, whether the signal was Hashing or not. The shortest response-tunes were obtained when flashing signals were seen against a steady background, and the longest with flashing signals against a flashing background. Thus it is concluded that flashing signals should not be used in conditions where a number of thorn may appear together within the field of view.