VOL. XV, NO. 2
OCTOBER 26, 1973
Test Your Ability
By CLARENCE WALSH
The natives in a certain tribe were similar yet different in one respect. Although they were physically alike, some of them were addicts of a drug which they obtained by chewing the leaves of a jungle plant.
This drug made them lie; otherwise they would have told the truth like their neighbors.
A stranger in the district met three of the natives. Having been told by his companions that only one of the three was an addict, he proceeded to find out which one it was.
When the stranger asked something that was indistinguishable, the second one pointed to the first one and said, "He says that he is not an addict." The third one pointed to the second one and said, "He is a liar." The stranger was able to deduce from these statements which one of the three was an addict. Can you?
The natives in a certain tribe were similar yet different in one respect. Although they were physically alike, some of them were addicts of a drug which they obtained by chewing the leaves of a jungle plant.
This drug made them lie; otherwise they would have told the truth like their neighbors.
A stranger in the district met three of the natives. Having been told by his companions that only one of the three was an addict, he proceeded to find out which one it was.
When the stranger asked something that was indistinguishable, the second one pointed to the first one and said, "He says that he is not an addict." The third one pointed to the second one and said, "He is a liar." The stranger was able to deduce from these statements which one of the three was an addict. Can you?
SOLUTION: If you start your deduction by assuming that the third native was telling the truth about the second, this would make the second one the liar, and he would be the addict. But if he was an addict, he would have been lying when he pointed to the first one and said he was not the addict.
We can deduce from this that the second native was not lying because if he had been lying, he would have been the addict, and the number one would have been the addict. From this we know that the second one told the truth, and the third native lied and was the addict.
We can deduce from this that the second native was not lying because if he had been lying, he would have been the addict, and the number one would have been the addict. From this we know that the second one told the truth, and the third native lied and was the addict.
