Timbre and Loudness on the Localisation of Sounds. 273 



of localisation of the variator sounds, I replaced the funnel-shaped mouth 

 first by an electric bell, later by a telephone buzzer, in the expectation of 

 obtaining more accurate and certain localisation when the sound was generated 

 on the perimeter instead of being conducted to it from the room outside. 

 The same diverse and erratic localisations were maintained. Some subjects 

 never localised the sound behind 90° v. if it was placed at 180° ; others never 

 localised in front of 90° v. a sound given at 0°. Here, for example, are the 

 records of two subjects, J. and Ss., for sounds of the buzzer (affixed to the 

 perimeter) at 0°, 90° v. and 180°:— 



J. Ss. 



0° 0° 0° 0° 0° 0° 180° 180° 180° 



90 120 90 90 90 90 135 135 135 



90 90 90 90 90 90 



0° 

 90 v, 

 180 



130 200 200 



Before I had obtained evidence of these striking individual differences in 

 localisation, I wondered whether inequalities in the reflexion of the sound 

 from the four walls of the room could be responsible for the gross errors met 

 with. Accordingly, on several occasions, I reversed the position of the subject, 

 testing him now with his face, now with his back to a given wall. With these 

 changes one subject was tested with the variator sounds, two subjects with 

 the buzzer sound conducted from the room outside, and one subject with the 

 bell ringing on the perimeter. But in no case was any change in localisation 

 relatively to the subject observable. If he had localised all sounds to his 

 rear in one position, he continued to localise all sounds to his rear in the 

 reversed position, and so on. 



This result is striking evidence of the influence of natural tendencies and 

 prejudices on the part of the subject in his localisation of sounds placed in 

 the median sagittal plane. The influence of expectation was also clearly 

 demonstrable by directing the subject's attention forwards or backwards at 

 the moment of the production of the sound, whereupon the apparent position 

 of the sound was generally changed in the sense of such direction of the 

 attention.* 



(b) For Sounds in the Horizontal Plane. — But if the ability to localise fore 

 and aft sounds in the median vertical sagittal plane is so defective, we should 

 not expect to be better able to localise fore and aft sounds placed along the 

 horizontal plane ; for both kinds of localisation are instances of what I 



* The following conversation between subject (S.) and experimenter (E.) will serve to 

 illustrate this feature : — S. " I expected a sound behind and I got it [sound given at 0°] 

 there." E. " Now try to imagine it in front " [sound at 0° repeated]. S. " Yes, I certainly 

 get it there, too." E. "Now try to imagine this sound [at 180°] behind." S. "Yes, 

 certainly it is there, but when I change my idea to its being in front, I get it there too.' 



