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Ravens display many sophisticated behaviors in the wild. Experiments suggest that these behaviors result partly from logical reasoning, not merely from instinct or rote learning. In one experiment, ravens were presented with food hanging on a string. To get the treat, a raven had to repeatedly reach down from its perch and pull up the string with its beak, stepping on the string after each pull to prevent slippage. Some ravens examined the situation for several minutes and then quickly performed this multistep procedure on their first try, without any preliminary trial and error. Since the ravens would not have previously encountered this situation in the wild, they could not have learned it through past experience. Hence, they apparently imagined possibilities and reasoned out what steps to take. In operant behavioral conditioning of laboratory animals, each step in a desired behavioral sequence is typically rewarded with food. Thus, the animal can learn each step without understanding how it contributes to the overall outcome of the behavioral sequence. But no one step in the pull-up sequence—except the last—was rewarded with food; the raven had to accomplish the whole lengthy sequence in order to eat. Skeptics might object, however, that each step was mentally rewarded simply because the food came nearer, not because the raven already understood which actions would have this effect. But that explanation seems implausible. If each step were acquired by trial-and-error learning, presumably numerous trials would be required, and the entire sequence would probably take months of training. Researchers modified the experiment to find out if ravens could have solved the puzzle by random movements that happened to be rewarding but were unsupported by logic. This time different ravens had to pull downward on the string to move the food upward. In this situation, the ravens often yanked on the string, occasionally bringing the food slightly closer. But no raven executed the full necessary sequence of motions, even though it was no more complex than in the first experiment. This suggests that the ravens found pulling downward to move food upward illogical and thus, unlike in the first experiment, could not deduce what actions were needed. : Reading Comprehension (RC)