How Math Explains the World.pdf

we already know that if they were asked the same question, they re-
sponded identically). There are nine different ways the pollsters can ask
the three questions. If the rule the husband and wife use results in three
yeses or three nos, the husband and wife will always answer their ques-
tions identically. If the rule the husband and wife use results in two yeses
and one no, let’s suppose that the answer to Questions 1 and 2 is yes and
to Question 3 is no.
The following table lists all the possibilities.

Husband’s Husband’s Wife’s Wife’s

Question # Response Question # Response

1 Yes 1 Yes

1 Yes 2 Yes

1 Yes 3 No

2 Yes 1 Yes

2 Yes 2 Yes

2 Yes 3 No

3 No 1 Yes

3 No 2 Yes

3 No 3 No

Notice that in five out of the nine cases (rows 1, 2, 4, 5, and 9 of the table)
the answers of the husband and wife agree. When the rule for answering
questions produces two yeses and one no, or two nos and one yes, the
answers will agree in five out of nine cases. When the rule for answering
questions produces three yeses, or three nos, the answers will always
agree. So if husbands and wives have evolved a question-answering rule, it
will show up in the data, because when the pollsters go into homes and ask
questions of each spouse at random, the husband and wife will produce the
same answer at least five times out of nine.
Convinced that they had the answer to the mystery, the pollsters exam-
ined their data. Surprisingly, the answers of husband and wife corre-
sponded approximately half the time. The pollsters concluded that
husbands and wives had not evolved a question-answering rule, but this
still left a mystery: Why, when they were asked the same question, did the
husband and wife always produce the same answer?
Simple, concluded one pollster: when the first spouse was asked a ques-
tion, he or she communicated which question he or she had been asked
and his or her answer; thus, when the second spouse was asked the same

All Things Great and Small 59