72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



These facts would suggest that many or most of the Squeaks 

 uttered by infants are produced when their tendency to keep in physi- 

 cal contact with a parent is thwarted. 



This may not, however, be true of all their Squeaks. Infants 

 clutching a foster parent or parent substitute may also utter Squeaks 

 just before shifting the position of their limbs of their own accord, 

 i.e., before they can have lost contact. Once, an infant which had 



9,000- 

 8.000- 



7.000" 

 6,000- 

 5.000- 

 4,000- 

 3.000- 

 2.000' 

 1.000 



I I 1- \ 



'A 



Fig. 19. — Two loud trilling patterns, intermediate between "pure" High Trills 

 and Screams, but most similar to the former. Uttered by an immature. 



Based upon a spectrogram by a "Sona-graph." 

 Each trilling pattern is a series of four notes or groups of components. Each 



of these series seems to be similar to the series shown in figures IS and 18, and 



to the components of the single Squeak and the intermediate between a Squeak 



and a Scream shown in figure 17. 



Additional harmonics, up to at least 18,000 c.p.s., accompanied these trilling 



patterns, but are not shown in the drawing. 



been quite silent while riding on my head suddenly began to utter 

 Squeaks when rain began to fall, in spite of the fact that it continued 

 to clutch me tightly. 



Such incidents would suggest that infants may utter Squeaks when- 

 ever they become "uncomfortable" or feel "frustrated" in any one of 

 several different ways. If so, their Squeaks can be considered a gen- 

 eralized distress reaction, strictly comparable to the "distress calls" 

 of many young birds. 



Of all the other platyrrhines I know, only infant tamarins of the 

 genus Saguinus utter distress notes as frequently as infant Night 

 Monkeys in similar circumstances. 



Under natural conditions, it seems likely that the parents of an 



