The Monkey as a Psychological Subject
Harry F. Harlow
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H. F. Harlow University of Wisconsin-Madison, Harlow Primate Laboratory
, 22 N Charter St,
Madison, WI 53715, USA
Many species in long-term captivity have tried to kill time by playing friendly games with their warders. In the end, only rhesus monkeys (Macaca mulatta) could tolerate the tedious hide-and-seek games that their human jailers prefer to play. In this article, written many years before the Stockholm syndrome was first described, the author relates how it was eventually discovered which species is most willing to contribute to the development of a genuinely scientific human psychology.
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Harry F. Harlow died in 1981 and Dr. Frank C.P. van der Horst () of Leiden
University stands as the person to addess correspondence to.
cups. While the animals watched, food was placed under one of the cups and after a
predetermined period of delay the monkey or ape was permitted to make a choice.
The previous research on the delayed reaction had indicated that this test should be
an excellent measure of general intellectual ability, and if this were true we believed
that maximum length of delay would correlate highly with the zoologists
conception of each of the monkeys and apes position in the phyletic scale.
The zoos collection of primates, the order of animals to which man belongs,
ranged from the lowest to the highest, from a lemur, an animal that looks more like a
fox than a monkey, to two chimpanzees and an orangutan, both of which are
anthropoid apes, the family of primates representing mans closest living kin.
The lemur fortunately was not one of the nocturnal species, and he cooperated to
the full extent of his limited capacities. He frequently behaved, however, in a most
unmonkeylike manner, and as often as not knocked over the cups with his nose
instead of his hands and picked up the food with his mouth instead of first grasping
it with his fingers. In spite of the fact that he failed to solve any but the shortest
delays, he was a well-mannered animal who accepted his position as imbecile of the
primate order with perfect grace.
The Vilas Park Zoo possessed two representatives of the New World monkeys, a
pair of cebus monkeys. These monkeys are best known as the only kind of animal
that with the aid of a hand organ and a tin cup can support a human being. Cebus
monkeys as we shall see have many virtues but their performances on delayed
reactions were far from spectacular. The animals were caged together and we could
not separate them. We speculated at the time that their limitations might stem largely
from emotional traits since they usually exhibited all the stability of a group of
5-year-olds during the closing hour of a birthday party, and subsequent research
confirmed, at least in part, our assumptions.
The Madison lab has always maintained a well-balanced collection of Old World
monkeys. When we began our work baboons were available, an enormous sphinx
baboon and a Hamadryas baboon, a living likeness of the appropriate Egyptian
hieroglyphic. The facility with which these monkeys solved delayed reaction
problems made it obvious that behind the doglike muzzles was a very advanced
Fig. 2 Apparatus for comparing
delayed response with stimuli in
horizontal and vertical position
brain, and the skill with which they displaced the cups demonstrated that walking on
ones hands does not destroy skilled coordination between fingers and thumb.
Perhaps there is something to be said for sitting on ones hands.
The baboons might be the finest test animals of all the monkeys were it not for
their size and intransigent dispositions. Tommy, the sphinx baboon was intellectually
endowed, but testing was difficult because after a few errors he would scream, crush
the cups, and smash the table against his cage. We finally solved the trouble because
this baboon fell head over heels in love with one of our testers, a pretty girl named
Betty. Tommy was one baboon that Betty literally had eating out of her hand, and
when Tommys memory failed in Bettys presence he blamed himself and not the
apparatus. Nevertheless, Tommys performance dampened our ardour for baboons as
standard test monkeys, for we doubted that we would always be assured of an
unlimited crop of beauteous and buxom Bettys to serve as testers (see Figs. 3 and 4).
The zoo possessed a number of guenons, slender, graceful, often aesthetically
colored, long-tailed Old World monkeys. These animals tested with variable skill;
indeed, there appeared to be a distressing positive correlation between their cost and
their proficiency.
Although we were not particularly impressed at the time we voted that very
satisfactory performances were made by a drab but relatively emotionally stable
monkey, the rhesus monkey, one of the sacred monkeys of India. This species
subsequently was to become the standard laboratory animal of research in
poliomyelitis and for psychobiological research as well.
The performances of the anthropoid apes on the delayed (...truncated)