680 TRANSACTIONS OF SUB-SECTION I. 
loudness of the whole sound was altered. In each case, especially by the latter 
procedure, the number of erroneous localisations became distinctly greater. The 
resulting confusion was just what would be expected if timbre and loudness are 
the base of sound localisation in the median plane. i 
The importance of timbre and loudness and the unimportance of spatial 
(? tactual) experience were further indicated by an experiment in which a 
subject, after having learnt to distinguish the positions of 0° and 90°, inserted 
two short rubber tubes, one in each ear. The result was to alter so markedly 
the timbre and loudness of the sounds that he had to learn afresh their correct 
localisation. 
These experiments suggest that the tactual impressions felt by the subject 
on their face and head are illusory, and that they are really of auditory origin. 
Just as when a sound stimulates one ear more strongly than the other it 
appears to hit that ear, or to be heard only in that ear, so when’a medial sound 
stimulates the two ears equally, it appears to hit the head or to be placed 
somewhere in the middle line. In each case, the spatial experience is a cue 
leading to head movement whereby the sound is more correctly localised. It is 
only with the growth of experience that median sounds are given a front, top, 
or back position; and even then the judgments are extremely inaccurate, 
especially when all auxiliary information is excluded. 
3. A Preliminary Note on Habit-formation in Guinea Pigs. 
By Miss E. M. Smrru. 
The observations on which this paper was based were carried out, under the 
direction of Dr. Myers, at the Cambridge Psychological Laboratory, during the 
present year. They form part of a larger scheme designed to test the 
inheritability in guinea-pigs of such characters as rapidity of learning, ability 
to profit by practice, accuracy of performance, retentiveness, &c. With this 
end in view, and in the hope of discovering well-marked individual differences 
of behaviour, the animals were subjected to certain tests. The tests used 
were :—(a) the labyrinth test, and (6) a new form of sensory discrimination test, 
in which photic and auditory stimuli were combined. Despite the fact that this 
preliminary investigation was, owing to its scope, necessarily somewhat general 
in character, it has nevertheless brought to light several hitherto unrecorded 
points of interest concerning guinea-pig behaviour. 
4. The Relative Fertility and Morbidity of Defective and Normal Stocks. 
By F. C. Surussaty, M.D. 
Observations have been made on the family history of children presenting 
some degree of educable mental deficiency and also of children who have gained 
scholarships. The chief points noted were the size of the fraternity, the order in 
the fraternity of the child under observation, and the number of members of the 
fraternity who had died by the time the individual round whom the record 
centred had reached the age of nine. 
Correlation between order in fraternity and size of fraternity :— 
Normal . -| 1,000 2°87 
| T | No. Order in | Size of e 
| ype Observed | Fraternity Present B 
‘Defective. .| 1,000 | 435 3:24 | 6-32 3:27 | 814-06 
| 216 | 4:79 2°55 65 + -008 
—| 
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