8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



they are close together if they are not also performing other 

 sexual patterns. 



A Night Monkey with dirt on its face sometimes removes the dirt 

 by rubbing the face along a branch. These reactions are actually rare, 

 but seem to be performed more frequently by Night Monkeys than 

 by any other platyrrhines with which I am familiar except the tamarins 

 of the genus Saguinus. 



Night Monkeys clean their hands and fingers by licking. 



The tabulation of autogrooming movements on page 7 also includes 

 the cleaning movements performed by the same individuals during 

 the same periods of observation. 



HOSTILE BEHAVIOR 



The term "hostile" may be applied to all behavior patterns resulting 

 from a tendency to attack and/or a tendency to escape. In this sense, 

 it is synonymous with the term "agonistic" as used in many other 

 discussions of behavior {e.g. Scott, 1958). 



The term "tendency" will be used in a broad sense throughout 

 this paper, to designate any "readiness to show a particular type of 

 behavior" (Marler, 1956). 



In preliminary and essentially descriptive accounts of behavior 

 based on observation rather than experiment, such as the present 

 account of the Night Monkey, it is usually not necessary to distin- 

 guish between a great number of qualitatively different tendencies. 

 Most social reactions can be characterized as the products of such 

 broad tendencies as attack, escape, gregariousness, copulation, pairing, 

 etc.^ 



^ The tendencies involved in the production of an otherwise ambiguous be- 

 havior pattern may be revealed by analysis of the other activities usually asso- 

 ciated with the pattern. Conversely, the term "tendency" may provide a con- 

 venient and concise way of summarizing the circumstances in which a behavior 

 pattern occurs. Thus, for instance, when a signal pattern such as a ritualized 

 posture or a vocalization (see below) is said to be produced by the attack 

 tendency, this means that an animal performing the pattern is likely to perform 

 overt attack movements during or immediately after the pattern and/or give some 

 outward indication that it "wants" to attack. When one signal pattern is said 

 to be produced by a stronger attack tendency than another signal pattern, this 

 means that the former is more likely to be accompanied or followed by overt 

 indications of attack than the latter and/or is likely to be accompanied or followed 

 by stronger indications of attack than the latter. (It should be stressed, in this 

 connection, that when a particular behavior pattern is said to be produced by 

 one or more particular tendencies it does not mean that other tendencies may not 

 be activated in an animal performing the pattern at any particular time.) 



