NO. 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN 75 



adults and/or by the same factors as their own Squeaks plus an 

 added component of alarm or escape. 



Some of the brief Squeaks or Squeaklike patterns of infants have 

 a slight "gulping" quality. They may be the source from which the 

 Gulps of adults are derived in the course of ontogeny ; but they cer- 

 tainly are not distinctive or well segregated when uttered by infants. 



Infants utter Hoots occasionally. To human ears, these sound very 

 much like slightly softer versions of the usual Hoots of adults ; but 

 sound spectrograms indicate that they are sometimes (at least) also 

 higher pitched and more broken up (see figure 20). They are usually 



i.oooi 



5,000 

 4,000 

 3,000 H K 



h 



2,000i 



,000 i ill ll 



^ , » » 1 1 r 



0.2 0.4 0.6 0.8 1.0 1.2 1.4 



Fig. 20. — Two Hoots, uttered by an immature male. 

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



uttered in series of two or three notes, apparently always when an in- 

 fant has become separated from its parents or parent substitute. Like 

 adults, infants usually or always sit still while uttering Hoots. Their 

 Hoots seem to be high-intensity patterns, produced when their desire 

 to be with a parent is stronger, or more strongly thwarted, than when 

 Squeaks or related intermediate notes are uttered. Thus, for instance, 

 an infant suddenly separated from its foster parent or parent substi- 

 tute may utter Hoots, intermediates between Squeaks and Screams, 

 and more or less pure Squeaks at first, then stop uttering Hoots but 

 continue the other notes, then stop the Screamlike notes but continue 

 Squeaks, and finally fall silent, as it gradually becomes accustomed 

 to being alone. Similarly, an infant accustomed to being carried 

 almost steadily by a foster parent is apt to utter relatively more Hoots 

 and fewer Squeaks than an infant used to being carried only occa- 



