THE 3 characters studied are (a) "passive defence reaction, " or shyness, T, as shown by tendency to run away at the approach of a stranger, hiding in a corner, dilation of pupils, muscular tetanus; (b) "active defence reaction " or aggressiveness, A [N.B. author uses no symbol] shown by attempt to bite; and (c) excitability, B, as shown by the manner of welcoming the master. It was observed that crossbreds from German sheep dogsx Giliatsky laika, neither of which are shy, are very shy. It was thought that shyness was transmitted by the laika, but whereas in the laika it was not manifested owing to a low level of excitability (b), in the hybrids it became manifested because excitability was greater (B.) This was confirmed by observations on the degree of excitability of 25 crossbreds from 5 such matings. At least 16 animals were B1 (very excitable), like the sheep dog, and the rest Bz2 (moderately excitable), but none were b like the laika. The mode of inheritance of T and A was studied on 300 sheep dogs and Airedales. Since the degree of manifestation of A is very variable, the animals were divided into only 2 well-defined groups, i.e. those showing or not showing the character in question (T v. t, and A v. a.) Crosses of T parents inter se produced 49 offspring, 45 T: 4 t; T X t gave 61 T: 53 t; and t X t, 9 T: 52 t. The data suggest that T may be a dominant or incompletely dominant character. Similar observation with A gave: A x A- 21 A: 2 a; A x a- 42 A: 28 a; a x a-28 a only. Thus A may also be a dominant. It is pointed out, however, that the conclusion cannot be absolutely reliable, owing to lack of objectivity in the method and environmental variability. It is also pointed out that it is erroneous to group A and T together under " defensive reaction." T is a natural reaction, widely spread among wild animals, whereas A was probably selected for by man. If the 2 reactions differ in origin, they probably differ genetically also. Pedigrees are given [figs. 4-7] which suggest the independent segregation of the 2 characters. Attempts were made to modify behaviour by cocaine. Doses of 0-0025 g. per 1 kg. of body weight injected to B dogs caused increased excitability. Injections to 3 Giliatsky]aika caused them to become more excitable and shy, a result which is in agreement with the author's hypothesis. In 2 other experimental series the effect of cocaine was measured by comparing the records of a pedometer which the dogs wore, before and after injection. In a preliminary experiment it was established that injection of physiological solution had no effect on rate of movement. In 13 A and 18 T dogs, injection of cocaine induced a marked increase of motility, as shown by the pedometer. The latter group also exhibited a marked increase of shyness, and the former of aggressiveness, i.e. cocaine intensified the normal type of behaviour. These results are also interesting in that they show that shyness is associated with increased, and not with depressed, excitability.
|Author Address||Lab. Dynam. Develop., State Univ., Moscow.|
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