1338 



HORMONAL REGULATION OF BEHAVIOR 



an attachment to a particular sleeping loca- 

 tion. 



Birch (1956j raised female rats with wide 

 rubber collars around their necks, which pre- 

 vented them from licking any part of the 

 body behind the neck. In particular, these 

 collars prevented access to the genital area, 

 which is intensively licked during pregnancy 

 and during the events associated with par- 

 turition. The collars were removed 1 to 2 

 hours before parturition. Birch states that 

 "because of the inadequacy of maternal be- 

 havior no offspring survived the nursing pe- 

 riod. The latent periods for the initial lick- 

 ing of the young were abnormally long." 

 Birch's hypothesis is that "the self-licking 

 of pregnancy is the experiential basis for 

 the self-licking . . . and the pup-licking of 

 parturition, and the pup-licking of the nurs- 

 ing period." Birch's data have never been 

 reported in full ; the report here quoted lacks 

 any statement about how many animals 

 were used, the duration of latent periods, 

 details of the survival of the young, quanti- 

 tative details of the behavior of the mothers, 

 etc. Coomans, in an unpublished study cited 

 by Eibl-Eibesfeldt (1958j repeated Birch's 

 study, using hooded rats (Birch used white 

 rats), and obtained quite different results. 

 He states that no disturbance of maternal 

 behavior was found if the collar was re- 

 moved before parturition, and that the dis- 

 turbances that were found when the collars 

 were left on could be attributed solely to 

 mechanical interference with the normal be- 

 havior pattern. Since neither the Birch nor 

 the Coomans study has been reported in 

 sufficient detail to permit a replication, it is 

 to be hoped that further work on this prob- 

 lem will provide data that will allow a more 

 confident interpretation. I have gone into 

 detail here only because so many authors 

 have referred to this experiment (Lehrman, 

 1953, 1956b; Hebb, 1953; Schneirla, 1956 j. 



Beach (1937) found that removal of vari- 

 ous amounts of cerebral cortex in female rats 

 caused a degree of disorganization of ma- 

 ternal behavior which was roughly propor- 

 tional to the amount of cortex removed. This 

 conclusion is based on measures of the 

 amount and the efficiency of nest-building 

 behavior, the time when nest-building be- 

 havior starts, efficiency of retrieving young, 

 measures of the amount of licking and clean- 



ing of the young, survival of the young, etc. 

 The disturbance of maternal behavior 

 caused by these lesions is due to more than 

 a specifically sensory deficit, since, e.g., ani- 

 mals with lesions of the visual cortex show 

 more disturbance of maternal behavior than 

 do peripherally blinded animals. Beach 

 (1938) further found that animals operated 

 on in infancy were superior in performance 

 to animals undergoing the same operation 

 as adults, although both were deficient when 

 compared with intact animals. The larger 

 the lesions, the greater was the degree of su- 

 periority of animals operated on at infancy 

 over those in which the lesion of the same 

 size was made after they became adults. 



These findings of Beach on the relative 

 effects of cortical lesions on maternal be- 

 havior when the lesions are made early in 

 life or later (greater effect of lesion in 

 adults than in infants, greater disparity 

 between the two groups with larger lesions 

 than with small lesions, effect of lesion a 

 function of size rather than of location, 

 etc.) are strikingly similar to those found 

 by Lashley (1929, 1933) who studied the 

 effects of cortical lesions of various sizes 

 on the learning of complex maze problems 

 in rats; the lesions were made in some ani- 

 mals after the problem was learned and 

 in others before the problem was learned. 

 Damage to the cerebral cortex interferes 

 much more with the retention of a previ- 

 ously learned problem than does a lesion 

 of the same size with the subsequent learn- 

 ing of the same problem. Further, the 

 disparity is greater, the larger the lesion. 

 Benjamin and Thompson (1959) found that 

 the ability of cats to discriminate different 

 degrees of roughness of sandpaper was more 

 seriously impaired by lesions in the somatic 

 sensory cortex when the lesions were made 

 at maturity than when they were made 

 at birth. Beach (1939a) found that the per- 

 formance of female rats in a maze-learning 

 situation was correlated with the efficiency 

 of their maternal behavior. For example, of 

 40 rats tested, the 5 which made the fewest 

 errors on the maze retrieved their first pups 

 after an average latency of 3.2 minutes; the 

 5 poorest maze learners took on the aver- 

 age 360.4 minutes to start retrieving their 

 young. 



These experiments of Beach hint that 



