were three individuals, Nos. 17, 20, and 25, who 
received a greater degree of punitive action from 
their associates than might have been anticipated 
on the basis of the low population density. When 
these three atypical 1947 females are removed 
from consideration the trends for the wounds and 
rate of maturation through these three periods 
more closely resemble that of the males. 
Each of these three periods of birth included 
individuals representing most of the range of the 
trap-proneness index. In order to separate the 
relationship between incidence of wounds or the 
rate of maturation and the proneness to enter 
traps from their dependence upon conditions 
associated with season of birth, the trap-proneness 
index for each sex was divided into low-, medium-, 
and high-class intervals, such that each interval 
was represented by approximately the same 
number of individuals. This analysis is shown in 
table 15. Shown in italics in this table are those 
trends which the author considers as being 
biologically significant. Thus with females the 
greater the proneness to enter traps the slower 
was the rate of maturation. The lack of any 
correlation between incidence of wounds and prone- 
ness to enter traps probably resulted from the fact 
that many of those females who matured rapidly 
were those which reared litters and engaged in 
considerable fighting during the time of lactation. 
This produced a higher incidence of wounds in 
this group than would otherwise have been the case. 
For males, which fight more than females, there is 
a good correlation between the proneness to enter 
traps and the degree of inhibition of the rate of 
maturation. However, it will be noted that the 
males which were most prone to enter traps had 
a more favorable rate of maturation than did 
those males with only a medium proneness to enter 
traps. This is due to the fact that a number of 
fairly rapidly maturing males continued to contend 
unsuccessfully for a higher social status, and in the 
process they received many wounds. The increased 
stress associated with this unsuccessful fighting 
probably produced this increased proneness to 
enter traps. 
An understanding of the dependency of prone- 
ness to enter traps upon those conditions which 
affect the rate of maturation is facilitated by an 
examination of the figures 80 A and B in which 
the maturity index is plotted against the trap- 
proneness index. For each sex the rats plotted in 
these figures are separated into five constellations, 
A to E. For each sex the constellations A, C, and 
D are somewhat arbitrary divisions in a continuous 
distribution in which those rats with lower rates 
of maturation (i.e. higher maturity index) are 
more prone to enter traps. The interpretation 
placed upon this relationship is that those condi- 
tions of social stress which inhibit growth reduce 
the tendency of rats to avoid noxious stimuli or 
situations deleterious to them. Although there 
was no way of completely determining the degree 
to which a heightened food drive, that may be 
more characteristic of rats with socially produced 
inhibitions of growth, may account for the greater 
tendency of such rats to enter baited traps, the 
author nevertheless believes it is the altered emo- 
tional state accompanying stress, that accounts for 
variability in proneness to enter traps rather than 
the hunger drive. 
Table 15. — The relationship of number of wounds and rate of maturation to the relative proneness to enter traps 
Number of wounds be- 
Sex 
Number 
Trap- 
proneness 
index 
(median) 
Maturity 
index 
tween age 
in days of: 
of rats 
(median) 
150-277 
(median) 
278-300 
(median) 
Females . 
22 
. 434 
/. 77 
1. 3 
5.0 
20 
.691 
I. 90 
0. 5 
3. 5 
22 
1. 448 
II. 10 
2.0 
3.0 
Males . 
23 
. 400 
I. 50 
7. 3 
6. 9 
27 
. 800 
II. 17 
2.3 
8.8 
23 
1. 286 
I. 86 
4. 4 
9.8 
(figures in italic represent those trends deemed by the author to be significant.) 
96 
