276 



Mr. C. S. Myers. The Influence of 



2. Localisation during Practice — 



(a) For Sounds in the Median Vertical Sagittal Plane. — The practice 

 experiments were carried out during several sittings, the number (cf. p. 272) 

 depending on the rapidity of improvement in the subject's accuracy of 

 localisation. The subjects were now told when they were right or wrong, 

 and only three positions of the sound were given — at 0° directly in front, 

 at 90° v. directly above, and at 180° directly behind an imaginary line 

 between the two ears. 



The final result was always to establish absolute accuracy in the localisa- 

 tion of the sounds. But the three positions were not learned with equal 

 ease ; consequently the total number of right answers varied with the 

 position of the sounds, the figures during relatively late stages of practice 

 with the variator sounds being — 



The criteria apparently employed during the subject's practice, in order 

 to distinguish these three positions, were (i) so-called "tactual" experiences; 

 (ii) right or left laterality ; (iii) difference in timbre, loudness, or nearness. 

 Of (i) further mention will be made later (pp. 280-283). Eeliance on (ii) 

 was only possible when the sound was not accurately produced in the 

 middle line ; if, for example, the rotating arm swung a little obliquely from 

 before backwards, the subject came to realise that when the sound was 

 heard (say) to his left it was placed (say) behind him, whereas when it 

 appeared to his right it lay to his front. In regard to (iii) various subjects 

 stated that at 0° the second was " fuller," " more voluminous," or " more 

 open," while at 90° v. it was " duller," " drearier," " more drony," or " more 

 booming," and at 180° it sounded "rather like an echo," "faint," " lacking in 

 assurance," " fuller than at 90° v., though very like it," yet " duller and more 

 distant than 0°." 



Similar results were obtained during practice when the telephone buzzer 

 took the place of the variators before the horn. 



(b) For Sounds in the Horizontal Plane. — In these experiments only three 

 subjects received practice for sounds placed at 45° h., 90° h., and 135° h., 

 but the results were precisely similar to those obtained for the sounds in the 

 vertical plane. Two subjects thought that at 90° h. they could distinguish 



electric bell and buzzer. Despite the practice gained in the ordinary room, their errors 

 increased by about 50 per cent, in the sound-proof room, showing clearly the influence 

 of the strange environment. Over 300 judgments were obtained. 



For 



0°.. 

 90 v. 

 180 .. 



80 per cent, of answers correct. 



