1318 



HORMONAL REGULATION OF BEHAVIOR 



so tested. Retrieving behavior began from 

 1 to 4 days after the young were introduced 

 into the cage. Leblond (1938) made simi- 

 lar observations in domestic mice. When he 

 tested 14 virgin female mice, none retrieved 

 young. After concaveation for 2 to 4 days 

 with young mice, 12 of the 14 began to re- 

 trieve. This procedure also induced retriev- 

 ing behavior in previously nonretrieving 

 hypophysectomized mice (Leblond and 

 Nelson, 1936, 1937a), and male mice (Le- 

 blond, 1940). 



The question arises whether the concave- 

 ation procedure really induced a change in 

 underlying physiologic condition, conducive 

 to the onset of retrieving behavior, or 

 whether it merely represents the sampling 

 effects of testing on a number of different 

 days, thus increasing the probability of 

 finding retrieving behavior in animals 

 whose readiness to retrieve varies from day 

 to day. As Wiesner and Sheard (1933) 

 point out, the evidence clearly favors the 

 assumption that exposure to the young does 

 in fact change the condition of the adult 

 being tested. Animals which are found to 

 retrieve without concaveation usually con- 

 tinue to retrieve throughout the period of 

 observation. In addition, removal of the 

 young after retrieving behavior has been 

 established through concaveation results in 

 the disappearance of the retrieving re- 

 sponse, as determined by tests some days 

 later. 



The nature of the physiologic change in- 

 duced by concaveation is not clear. Since 

 concaveation induces retrieving behavior in 

 hypophysectomized mice (Leblond, 1937, 

 1940), we cannot assume that its effect is 

 through the stimulation of hormone secre- 

 tion. As we have noted in connection with 

 other aspects of retrieving behavior, there 

 are certain similarities between effects of 

 the young on retrieving behavior and on 

 the nest-building behavior observed by 

 Roller (1952, 1956). Both can be induced 

 by confining young with the animals being 

 tested, and both can be induced in hypo- 

 physectomized animals. However, Weisner 

 and Sheard (1933) found that individual 

 rats in which retrieving was induced by con- 

 caveation would not necessarily show aiiv 

 onset of nest-building behavior associated 

 with this retrieving. We must thus reiterate 



that, whereas the physiologic bases of nest- 

 building and of retrieving (at least in do- 

 mestic rats and mice) undoubtedly have 

 much in common, they are probably not 

 identical. 



(6) Stimuli eliciting retrieving responses. 

 The stimuli by means of which young ani- 

 mals induce retrieving behavior on the part 

 of the parents may vary considerably from 

 species to species, although information on 

 this problem is fragmentary and incom- 

 plete, even for most of the widely used ex- 

 perimental animals. Scott (1945) reported 

 that domestic sheep respond to the sounds 

 of their bleating lambs, and Beach (1951) 

 observed that the squeals uttered by young 

 laboratory rats in response to painful stimu- 

 lation elicit greatly increased activity in 

 the lactating female. Similar observations 

 have been made on wild meadow mice (Bai- 

 ley, 1924) and rice rats (Svihal, 1931). Ac- 

 cording to Zippelius and Schleidt (1956), 

 young of the common vole, domestic mouse, 

 and European yellow-necked mouse induce 

 retrieving behavior on the part of their par- 

 ents, in part, by uttering supersonic cries 

 with frequencies in the neighborhood of 70 

 to 80 kc. Domestic cats retrieve their young 

 in response to the cry given by a kitten sep- 

 arated from its mother (Leyhausen, 1956). 



Auditory and visual stimuli are also ef- 

 fective. Anesthetized young European yel- 

 low-necked mice may be found and re- 

 trieved by their mothers, although only if 

 the mother passes close to them, in contrast 

 to active young, wdiich attract the mothers 

 from a considerable distance by their super- 

 sonic calls (Zii)pelius and Schleidt, 1956 1. 

 Dieterlen (1959) and Eibl-Eibesfeldt 

 (1958) have made observations which sug- 

 gest that olfactory stimuli are effective in 

 inducing retrieving behavior in the golden 

 hamster and laboratory rat. 



Beach and Jaynes ( 1956a, c) have shown 

 that several different sensory modalities 

 contribute to the stimulation of maternal 

 retrieving behavior in the laboratory rat. 

 The importance of olfaction is demon- 

 strated by the following facts: peripherally 

 blinded females spent more time investigat- 

 ing a small cage made of fine copper-wire 

 mesh containing a young rat than they did 

 a similar cage containing no young rat, 

 whereas arosmic females failed to distin- 



