The Paradox of Self-Destructive Choices

Abstract

Many pathological problems that are prevalent in modern society, such as undersaving, overborrowing, credit-card bankruptcy, and lifestyle-related diseases (obesity, smoking, drug abuse, and gambling addiction), are all closely related to the choices made by the people who constitute the society. People sometimes overborrow money in order to spend it on leisure and/or luxury items, overeat, spend indulgent times, smoke, and gamble to the point of destitution. In all of these situations, the results of the choice to engage in such behaviors have adverse effects on the individual’s future. Moreover, self-harmful behavior is not always limited to the extreme cases described above. For example, on occasion, we sometimes stay up drinking until late at night even though we have a meeting early the next morning. As another example, rather than completing an important task with an impending deadline, we often engage in trivial tasks such as cleaning our work desk, checking e-mails, and self-grooming.

Appendices

Supplement A: Monkeys and Chōsan-Boshi?

Chōsan-boshi (“three in the morning, four in the evening”) is a story that ridicules how monkeys become preoccupied with immediate rewards. There was actually a psychological experiment that used 11 monkeys consisting of different species—six cotton-top tamarins and five common marmosets —wherein their impatience was measured (Stevens et al. 2005). In this experiment, Jeffrey Stevens and his joint researchers at Harvard University measured the impatience of monkeys by offering the monkeys (A) two treats that they could eat immediately or (B) six treats for which they would have to wait before they could eat; they observed which option they would choose and repeated the procedure by changing the wait time for (B). The treats, weighing 45 mg each, were banana-flavored.

The results showed that, on average, marmosets waited 14.4 s and tamarins waited 7.9 s. That is, even when the amount of treats is tripled, they could wait for only a moment that was as short as taking a few breaths. We can see that the impulsiveness and impatience of the subjects are not even close to that in chōsan-boshi.

However, that was not what caught Stevens and his colleagues’ attention. It was the fact that there was a large difference in impulsiveness between two species of monkeys whose longevity, body type, brain size, and ecology—including their social life—were not overly different. The difference in impulsiveness was much more significant when the individual monkeys were compared: even the most patient tamarin (who was able to wait for 9.8 s) was much more impatient than the most impatient marmoset (who was able to wait for 10.0 s).

Stevens and his colleagues attribute this result to differences in the subjects' staple diet, tree sap or insects. This is because, whereas patience is required to wait for tree sap to seep out, impulsiveness works well when hunting for insects. In fact, while marmosets obtain approximately 70 % of their diet from sap seeping from trees, in the case of tamarins, only about 14 % of their diet depends on tree sap; a vast majority of their nutrition comes from insects. Stevens and his colleagues speculate that natural selection worked under these differences in food ecology by improving the ability to self-control among marmosets, which are required to have patience, while depressing the ability to self-control among tamarins, which are required to have impulsiveness.

As for problems relating to impulsiveness and self-control—an important subject in this book—I will discuss these in detail in Chap. 3.

Supplement B: Measuring Personal Discount Rates

As explained in the main text, one rarely asks “What interest rate do you want for waiting to receive the payment for one year?” to actually measure the time-discount rate; that is because it is difficult for people to respond to such a question by accurately stating the exact interest rate that they want. One would normally ask a series of two-choice questions, such as “Do you want (A) to receive JPY 10,000 today or (B) to receive JPY 10,191 one year later?”, and estimate through statistical methods the amount of money 1 year later that would have the same value as today’s JPY 10,000.

Before proceeding to the next paragraph, please try to measure your own subjective discount rate by answering the question shown in Table 1.1.

Table 1.1 Questionnaire to measure personal discount rates

In the table, the interest rate for choosing (B) becomes larger as you go down. Because the interest rate increases as you make your choice one by one from the top line, you are likely to switch to (B) at some point, even if you had chosen (A) (i.e., receiving JPY 10,000 today) at the beginning. The point at which you make your switch is where you will find your subjective discount rate. The subjective discount rate is higher for those who are slow to switch.

In an economic experiment , you would ask the subjects to choose from similar options, after promising to pay the amount of money that he or she chooses at the specified timing. However, because it is impossible to budget to pay all the subjects what they choose in each line, the payment is normally made in a drawing. In addition, since the responses could be biased based on the order, the lines may be listed randomly rather than in order as shown in this example.