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   [[circled]] 28 [[/circled]]
[underline]]Ateles[[underline]] ssp, Nov. 14,1959, IV

forward. What she does then is follow the hand hand for a while, continuing to utter yells while she does so,and then stops following and shut up at the same time. Similarly, she will continue [[Trills]] for a few seconds or minutes after being taken off me, but will shut up if the Trill's  don't result in her being taken up again. In other words, she continues [Trill's] as long as she thinks there is any chance of being allowed to grasp the parent or parent substitute, but she doesn't continue them indefinitely, no matter now unhappy she may be at being still left alone. Content with the "Lost call" vocalizations of baby Howlers. Could evidence that the Lost call Trill's of the baby spiders are definitely social signals. [[?]] evidence that they are very rapidly "exhausted" or negatively conditioned", temporarily, when they don't produce the appropriate result.)
(Another interesting aspect of the stimuli producing the Lost Call Trill is the way in which new stimuli can release them again after they have temporarily subsided.  Thus, for instance, if I take the little animal off my hand and put her on the table close by me, she will utter a lot of Trill's for a few seconds but then subside if I don't allow her to climb back on me. Then, however, if I get up and go out of the room, she will utter a whole new burst of Trill's from the moment I start to leave until a minute or so after I have disappeared. Usually without attempting to follow me.  Incidentally, this sort of behavior may be good evidence that the stimuli releasing infantile behavior and distress calling can be purely visual.)
(Also in connection with stimuli, it should be mentioned that this little animal, like all other baby monkeys of other species I have kept, definitely prefers to grasp and/or sit on a turkish towel rather than the flat surface of the table or the floor.) The only other circumstances I have ever heard Trill's uttered in were once or twice when I ran cold water over the little animal; and once