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ThePuzzling Puzzles of H a r r y a r l o w n dE d w a rD e c i H a d

- r -- -o scientists conducted I n the middle of the last century two young --_--_ ,' a I experiments that should have changed the wodd-but did not. Hury F. Harlow w,rs a professor of psychology at the University of Wisconsin who, in the L940s, establishedone of the world's first laboratoriesfor studyingprimate behavior.One day inL949,Harlow and two colleagues gathered eight rhesus monkeys for a rwo-week experiment on learning. The researchers devised a simple mechanicalpuzzle like the one pictured on the next page. Solving it required three steps: pull out the vertical pin, undo the hook, and lift the hinged cover.Pretty easyfor you and me, far more challenging for a thirteen-pound lab monkey. DRIVE

Harlout\ pzzzlc in tbe starting (left) and soloed (rigbt) positions,

The experimenters placed the puzzles in the monkeys' cages to observe how they ssa6lsd-2nd to prepare them for tests of their problem-solving prowess at the end of the two weeks. But almost immediately, something strange happened.Unbidden by any outside urging and unprompted by the experimenrers, the monkeys beganplayingwith the puzzles with focus, determination, and what looked like enjoyment. And in short order, they began figuring out how the contraptions worked. By the time Harlow tested the monkeys on days 13 and L4 of the experiment, the primates had become quite adept. They solved the puzzles frequently and quickly; two-thirds of the time they crackedthe code in lessthan sixty seconds. Now, this wasa bit odd. Nobody had taught the monkeys how to remove the pin, slide the hook, and open the cover. Nobody had rewarded them with food, affection, or even quiet applause when they succeeded. And that ran counrer to the acceptednotions of how primates-including the bigger-brained, less hairy primates known as human beings-behaved. scientists then knew that two main drives powered behavior. The T h e P u z z l i n g u z z l e s f H a r r yH a r l o wa n d E d w a r d e c i P o D first was the biological drive. Humans and other animals ate ro sare their hunger, drank to quench their thirst, and copulated to satis$t their carnal urges. But that wasn't happening here. "Solution did not lead to food, water, or sex gratificadon," Harlow reported.l But the only other known drive also failed toexplain the monkeys' peculiar behavior. If biological motivations came from within, this seconddrive came from withoug-shs rewardsand punishments the environment delivered for behaving in certain ways. This was certainly true for humans, who respondedexquisitely to such external forces.If you promised to raise our pay, we'd work harder. If you held out the prospect of getting an A on the test,we'd study longer. If you threatened to dock us for showing up late or for incorrectly completin g a form, we'd arrive on time and tick every box. But that didn't account for the monkeys' actions either. As Harlow wrote, and you can almost hear him scratching his head, "The behavior obtained in this investigation posessome interesting questionsfor motivation theory, since significant learning wasattained and efficient performance maintained without resort to specialor extrinsic incentives." \What elsecould it be? To answer the question, Harlow offered a novel theory-*5ua "The amounted to a third drive: performance of the task," he said, "provided intrinsic reward." The monkeys solved the puzzles simply becausethey found it gratifying to solve puzzles. They enjoyed it. The joy of the taskwas its own reward. If this notion was radical, what happenednext only deepenedthe confusion and controversy. Perhaps this newly discovered drive"intrinsic Harlow eventually called it motivati6n"-q/as real. But surely it was subordinate to the other two drives. If the monkeys were rewarded-with raisins!-for solving the puzzles, they'd no doubt perform even better. Yet when Harlow tested that...
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