1334 



HORMONAL REGULATION OF BEHAVIOR 



bred in small cages, and had not been tested 

 for retrieving during their first breeding ex- 

 perience; therefore, they had had practi- 

 cally no experience in retrieving. Beach and 

 Jaynes found that retrieving efficiency in- 

 creased during the first 7 days postpartum, 

 for both primiparas and multiparas. This 

 improvement was a function of practice, 

 because it did not occur unless repeated 

 testing provided practice. Animals tested 1 

 day postpartum during their first and their 

 second lactation periods showed no im- 

 provement. 



On the basis of these data, it is not pos- 

 sible to say whether the difference between 

 Beach and Jaynes' conclusions and those 

 of Leblond are due to differences in the 

 amount of retrieving practice obtained by 

 the animals during the first lactation period, 

 to differences in testing methods, or to dif- 

 ferences between rats and mice. 



Nice (1937) observed that inexperienced 

 song sparrows building their first nests 

 seemed to build just as well as did experi- 

 enced birds. Marais (quoted by Armstrong, 

 1947) reared four generations of weaver 

 finches, a bird which normally builds a very 

 elaborate nest, without giving them the op- 

 portunity to see any nesting material. Their 

 descendents plaited their elaborate nests in 

 a normal manner. Hinde (quoted by Thorpe, 

 1956) found that canaries that had never 

 had an opportunity to manipulate nesting 

 materials would, when given grass for the 

 first time, pick it up and carry it to the 

 nest-pan within a minute or so. Observa- 

 tions such as these indicate that, in many 

 birds, nest-building behavior is rather rig- 

 idly determined by organic influences. How- 

 ever, Lorenz (quoted by Thorpe, 1956) 

 noted that ravens and jackdaws that are 

 building nests for the first time are uncer- 

 tain what material to use, and must learn 

 to pick material that can be woven into the 

 nest. Hinde (1958) found that a chaffinch 

 kept in a cage without nesting material de- 

 veloped the habit of plucking its own feath- 

 ers to use as nesting material (as do many 

 canaries). In the following year, when it 

 was kept in an aviary with plenty of nest- 

 ing material, it plucked its own feathers 

 nevertheless. Lehrman (1955) reported that 

 ring doves breeding for the second time 

 tended to feed their squabs sooner after 



hatching of the eggs than they liad at thcii- 

 first breeding. 



(6) Learning or physiologic change? It is 

 reasonably clear that, in many animals, 

 there is some improvement in the efficiency 

 of parental behavior between the first and 

 subsequent breeding experiences. However, 

 the method used for collecting most of 

 these data is unsatisfactory in several re- 

 spects. Fii'st, the fact that animals engaged 

 in parental behavior are in a constantly 

 changing physiologic condition means that 

 changes in behavior occurring, for example, 

 late in lactation, which might be influenced 

 by experiences earlier in lactation, cannot be 

 expected to be transferred intact to the be- 

 ginning of the next lactation period (when 

 the animal is in a different jihysiologic con- 

 dition). Thus, it would be very difficult, by 

 this method alone, to demonstrate the pos- 

 sible importance of concurrent experiences 

 as a factor in the changing pattern of be- 

 havior which is so characteristic of the 

 parent-young relationship. 



Secondly, many of the conclusions about 

 imiM-oved eflSciency of maternal behavior in 

 second and later parturitions are based on 

 observations in which there is no adequate 

 control for the age of the animal at the time 

 of the observation, and for the purely phys- 

 iologic effects of the animal's having gone 

 through the endocrine changes associated 

 with the first breeding experience. Dieterlen 

 ( 1959) reports that female golden hamsters 

 which give birth for the first time before 

 they are 80 days old often build abnormally 

 small nests, and fail to care for the young 

 properly because they are easily frightened. 

 However, females that do not give birth 

 until they are more than 3 months old are 

 almost always more careful and quieter, 

 even during their first lactation period. 

 Seitz (1954, 1958) found that scores indi- 

 cating the efficiency and intensity of ma- 

 ternal behavior were higher in rats breeding 

 for the second time than in those breeding 

 for the first time. This difference is asso- 

 ciated with a tendency toward increased 

 litter size and greater frequency of litters as 

 the mother matures. Seitz states that as the 

 mother rat grows still older, litter size and 

 maternal behavior tend to decrease. This 

 raises the question as to whether the in- 

 crease observed between the first and sec- 



