Furthermore, Seitz found that these members of 
larger litters more frequently avoided entering a 
strange situation in the form of a differendy struc- 
tured cage placed temporarily at the open door of 
the home cage. This observation is in apposition 
to that of free-ranging rats. However, the con- 
ditions surrounding the experience of the free 
ranging rats were quite different. They were 
frequently exposed to emotionally disturbing con- 
ditions up to the time at which the observations of 
reduced avoidance were made. That is emotional 
disturbance and stimuli leading to its origin was 
the normal rather than the unusual situation. 
One might then anticipate that these disturbed 
rats would actually seek out situations which 
fostered reestablishment of their normal state of 
physiology. It is for this reason that I believe that 
the third hypothesis is the best tentative one for 
explaining the origin of this masochistic type 
behavior by socially low-ranking free-ranging rats. 
The strange object reaction, social stratification, 
and periodicity of activity are interrelated phenom- 
ena; even though the basis of this interrelationship 
is by no means clear. In addition to the “bold” 
rats who come out early in the evening, and their 
stronger associates who appropriate their trans- 
ported food, Chitty and Southern cite another type, 
one which never goes to the original food source 
but resorts to gleaning morsels dropped by other 
rats after transport to the vicinity of the harborage. 
These observations support my contention that 
social behavior is a major determinant of periodic- 
ity of activity. 
Thompson (96) provides some detailed data on 
the activity of 10 marked rats at a pig farm over a 
period of 5 nights. The number of visits to a hopper 
of wheat during each 5-minute interval was re- 
corded for each marked rat. From his data I 
attempted to verify further the belief that there is 
a time stratification of activities of different mem- 
bers of a population. There was considerable 
overlap of periods of activity, and yet a cursory 
examination of Thompson’s histograms for these 
10 rats indicated differences in periodicity. Two 
indices of periodicity were taken: (a) The first 5- 
minute interval during which the rat visited the 
bait; (b) The midpoint time of activity. For each 
rat the latter index was the particular 5-minute 
interval, before and after which equal number of 
visits were made to the wheat. Each day the 10 
rats were rank ordered according to these indices 
of times of activity. The fifth day was omitted 
since by that time a nearly 6-hour forward shift in 
activity had occurred so that differentiation of 
individuals on a time basis was difficult and for 
some reason the two rats which usually showed up 
last at the bait failed to make their appearance. 
These data were amenable for determining if the 
order of visiting the food was consistant from day 
to day (97). When r=rows (rats) and c=columns 
(days); T,= totals across rows (i.e. sum of ranks 
for days 1 to 4). 
(r-l) + (c-l) irf 
cr(r-fl) J|_£i 
T\— 3c(r+l)J 
X 2 = 23.54; p less than .01 for 1st visit. 
X 2 =23.71; p less than .01 for midpoint time at 
bait. 
This argues for the reality of the stratification of 
colony members over time with reference to these 
specific portions of their overall activity at the bait. 
A contingency test of Chi Square for the similarity 
of mean rank between the two indices (table 70) 
gave a X 2 of 3.44; p ~ .95. We are therefore on 
fairly sure ground for believing that the entire 
condensed period of time of activity of each rat has 
the same rank ordering as reflected by the indices. 
Schematically the stratification of these rats through 
time is shown in figure 155. Two of the rats, N 
and U did not appear until the food was nearly 
exhausted. In contrast to the other eight rats the 
number of visits by these two rats exhibited a 
marked decline on successive days until by the fifth 
day neither appeared. Thus, time stratification 
can result in complete exclusion from a limited 
source of reward. 
Table 70. — Mean rank-order of the visitation of rats at a pan of 
bait during the first four days of its availability ( based on data from 
Thompson , circa 1953) 
Rat 
Rank of first 
visit to bait 
Rarik of mid- 
point time of 
visits to bait 
1 
3.63 
3. 38 
2 
4. 00 
3. 88 
3 
3. 00 
3. 00 
4 
7. 75 
6.83 
N 
9. 63 
8. 25 
O 
3. 38 
4. 88 
P 
4. 63 
5. 13 
S 
6. 25 
6. 50 
u 
8. 88 
9. 75 
X 
3. 88 
4. 63 
283 
