disease organisms or learned behaviors as the bits 
of information. In either case one might anticipate 
a threshold for frequency of contacts necessary to 
insure transmission of a message. Below the 
effective threshold of contact frequency each 
contact represents noise as conceptualized by 
information theorists. Contacts by rats, who have 
only a moderate number with each of two groups, 
may be classified as noise. Since this category 
of rats is reduced by nearly half in a population 
organized into ingroups, such organization effec- 
tively reduces noise. Those rats with a moderate 
number of contacts with one group but many with 
another should be the most effective messengers. 
Although this category of rats remains a small 
proportion of the total, the organization of the 
population into ingroups produces a threefold 
increase of this category. 
These interpretations of table 40 are patently 
quite hypothetical insofar as transmission of 
information is concerned. However, the logic 
of this analysis clearly shows that where a certain 
threshold of contacts does result in the transmission 
of information, advantages accrue to populations 
organized into ingroups because: (1) The amount 
of noise is reduced and, (2) the number of effective 
messengers is increased. 
5. Sociality 
A. Social Rank and Social Stress. Membership 
in an ingroup assures that the individual will most 
likely share in the advantages or disadvantages 
experienced by the other members of that group. 
Even the most cursory observations of local 
groups soon revealed much similarity among mem- 
bers as to physical characteristics, past history, 
behavioral traits, and types of experiences. De- 
spite similarity within groups, marked differences 
existed between groups with regard to these vari- 
ables. This stratification of groups indicated a 
class structure of the population. To understand 
what I imply by social classes requires an exami- 
nation of my delineation of social rank of individ- 
uals, since social class is in essence the mean social 
rank of the component members. Social rank is 
considered as equivalent to the likelihood of a rat 
satisfying its drives. Its associates may facilitate 
or interfere with this satisfaction of drives, it is 
difficult to measure such satisfaction directly. 
Practically one must rely on observable character- 
istics or conditions which presumably reflect the 
degree to which rats satisfy their drives. Some of 
these criteria represent causes and others conse- 
quences of evolving social rank. When a rat ex- 
periences much difficulty from its associates in 
satisfying its drives it is considered as being in a 
high state of social stress. Thus social rank and 
social stress are negatively correlated abstractions. 
In this section and those that follow I shall attempt 
to define criteria for arriving at conclusions of 
social rank and stress, and will then document how 
these are exhibited by the rats. In these discussions 
it will be impossible to separate clearly cause 
and effect. 
B. Criteria for Judging Social Rank include the 
following: 
a. Proximity to goals: If a rat lives nearer to a 
goal than do some of its associates, it will be pos- 
sible for it to reach that goal and make a satis- 
factory response, without so frequently encountering 
a rat which is not a member of its own local colony. 
The term goal is used in the sense of an object 
(this may be another rat) with respect to which a 
response may be made that satisfies some need 
felt by the organism. Assume that there are two 
individuals A and B, of which B lives farther away 
from a goal than does A, and also that B has to 
pass near A’s place of residence en route to the goal. 
In this situation A can more easily detect whether 
there is another individual at the goal — even be- 
fore it has left the immediate vicinity of its burrow. 
However, the critical point is that B must pass 
near A’s place of residence. At this time any 
interaction between A and B will interfere with the 
time sequence of B’s reaching the goal and satis- 
fying a particular need. After repeated experience 
with such a situation one might anticipate that B 
would attempt to avoid A regardless of what the 
nature of their interaction had been. Once this 
avoidance behavior had been initiated it is easy to 
see how A might then attack B, and thus there is 
developed territorial defense in which the rat 
living farther from the goal is at a disadvantage. 
As the relationship between A and B is developing, 
it must be remembered that there is a greater 
probability that A will be satiated with respect 
to the reward arising from responding to the goal. 
This formulation offers the most logical explana- 
tion of the observed situation which existed in the 
pen with reference to the source of food and water 
as goals. The social system was soon structured so 
that rats living nearer the Food Pen, that is in the 
alleys, exhibited dominant behavior over rats 
176 
