100 
10 
</> 
t- 
< 
<r 
u. 
o 
cr 
UJ 
CD 
5 
3 
Z 
I 
J 
Figure 119. — Average pattern of frequency of association 
by all individuals in the population with members of 
ingroups and randomly composed groups. Each set of 
points is the average of four groups of six rats each. No 
individual rat had more than seven recorded paired 
associations with the members of a random group. All 
rats with more than seven paired associations with the six 
selected members of an ingroup are apparently members 
of that ingroup. By this method of analysis rats form 
ingroups of from 1 0 to 15 individuals. 
members of the population, it is possible to approxi- 
mate the real size of the ingroup. On the basis of 
the figured average results, the size of the ingroups 
must have been between 10 and 15 rats, although 
only 5 to 8 members of the ingroup were selected 
for the purpose of the tabulation. 
Seven was the greatest number of associations 
any of the 155 rats had with a random group. 
Therefore, any rat having over seven paired associa- 
tions with one of the four suspected ingroups was 
assigned as a member of it. On this basis the addi- 
tion of new members was: eight for the East Alley 
Ladder ingroup; four for the Female 44 Lead 
ingroup; four for the Box 25 Burrow ingroup; and 
three for the South Alley Burrow ingroup. This 
latter group lost one member. Thus the total 
sizes of the ingroups were 14, 12, 10 and 8. 
• = WITH THE INGROUP 
■ = WITH THE RANDOM GROUP 
THE INGROUP • 
• • 
• • 
• • • 
5 10 15 
NUMBER OF PAIRED ASSOCIATIONS 
Figure 119 permits a generalization regarding 
the structure of the ingroup. It is logical to equate 
affinity to the group with the number of associa- 
tions a rat has with its members. Thus, there is a 
single rat with greatest affinity and an increasing 
number with lesser and lesser affinity. No sharp 
demarcation can be made between marginal mem- 
bers of the group and nonmembers, who by chance 
have an increased number of contacts with the 
members of the group. The rat with the greatest 
affinity to the group may be considered a leader, 
primarily in the sense that by its more frequent 
membership, it has a greatest opportunity to exert 
an influence upon the other members of the group. 
Table 39C . — Number of paired associations with the 
East Alley Ladder ingroup 1 
Rat 
number 
Sex 
Paired associations of successive 
analyses 
A 
B 
C 
Total 
54 
M 
8 
6 
5 
19 
56 
M 
72 
11 
11 
34 
59 
M 
9 
11 
15 
35 
57 
M 
7 
9 
7 
23 
60 
F 
71 
14 
16 
41 
83 
M 
6 
8 
6 
20 
99 
M 
8 
21 
15 
44 
657 
M 
10 
12 
9 
31 
659 
F 
8 
10 
12 
30 
662 
M 
11 
15 
17 
43 
669 
M 
12 
13 
10 
35 
749 
F 
1 
14 
11 
32 
868 
M 
11 
12 
11 
34 
873 
M 
10 
10 
6 
26 
1 Italicized figures indicate the rats assigned as the ingroup 
for the purpose of successive analyses. 
A more detailed analysis was prepared for one 
of the presumed ingroups, the East Alley Ladder 
Association (table 39C). The 14 rats with the most 
associations with these 6 rats are shown in Column 
A. Utilizing the six rats with the most associations 
as the central memlx'rs of the group, another tabu- 
lation was prepared of the associations with them 
by the population. This process was repeated 
again, and the rats with the most associations are 
shown in Columns B and C. By this stepwise pro- 
cedure, it was possible, to more accurately delineate 
the membership and size of the group. Two rats, 
Nos. 60 and 99, not noted in the original group, 
proved to have the greatest affinity to the group; 
174 
