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Mr. C. S. Myers. The Influence of 



have termed incidence. Laterality can only concern whether the sound is 

 placed to the right or left of the subject or somewhere in the median line ; 

 and, as I have already said, errors in laterality were never found in these 

 experiments, provided that the auditory acuity of the subject's two ears was 

 normal and that the position of the sounds relatively to the two ears was such 

 as to produce the required binaural difference (or equality) of loudness. On 

 the other hand, whatever factors are responsible for the determination 

 incidence should hold for the horizontal, as well as for the median 

 sagittal, plane. 



Experiments carried out on five subjects with variator sounds given in the 

 horizontal plane reveal just the same inaccuracies as have been described for 

 the median sagittal plane. The first of these subjects localised all sounds — 

 whether fore (45° h.), side (90° h), or aft (135° h.)— behind his ear, the 

 second localised them all in front of his ear, the third localised fore and aft 

 sounds in front of his ear, while the fourth and fifth subjects gave too 

 variable a localisation to allow of any more general statement than that 

 they showed total inability to distinguish fore, side, and aft sounds from one 

 another. 



Two questions naturally arise : — How is it that previous observers, while 

 recognising a liability to err in the localisation of such sounds, have not laid 

 stress on the initial grossness of the errors of localisation revealed under the 

 conditions of these experiments ? How is it that these errors do not play an 

 equally prominent part in our everyday life ? We are all aware of occasional 

 errors in fore and aft localisation, but it is relatively seldom that they are 

 brought to our notice. 



Now, one important factor consists in familiarity with the sound. As we 

 shall see, with practice every subject learned to localise correctly. Another 

 important factor employable in everyday life, but eliminated to a very large 

 extent in these experiments through the use of a head rest, consists in head 

 movement. On several occasions in the course of these experiments I 

 expressly instructed my subjects to move the head while they were listening 

 to the sound, whereupon their errors in localisation were immediately and 

 often quite accurately corrected. 



In some experiments, moreover, performed in the open air, in which I 

 acted as subject, where the vowel E was spoken by an assistant and his 

 position had to be ascertained, I localised both fore and aft positions forward, 

 but when the experiments were repeated with a small head movement 

 carried out during the production of the sound, I at once changed the 

 localisation of the rearward sounds from fore to aft. 



Obviously, by turning the head, the sound is alterable in intensity ; for, 



