Cobas AM: Nueva Gestora de Francisco García Paramés

Loss aversion is only one of many behavioral biases discovered by psychologists like Tversky and Kahneman. Just as the human eye is susceptible to optical illusions, the human brain is susceptible to illusions about risk and probability. Even simple decisions can be challenging when risk is involved.

Another illustration of this fact is a simple game that I’ll call the “Psychic Hotline.” You’re sitting in front of a computer screen, and every sixty seconds, one of two letters appears on the screen, A or B. The object of the game is for you to predict which letter will appear next by pressing the “A” or “B” key before the letter appears. If you’re correct, you’ll get paid $1, but if you’re wrong, you’ll lose $1. This game is repeated many times so your accumulated winnings and losses will go up or down depending on how well you predict each outcome. It doesn’t sound like a particularly engaging game, but anyone who has ever seen people sit in front of slot machines for hours, inserting one coin after the next, knows that it doesn’t take much to capture a player’s interest. They don’t call these machines “one-armed bandits” for nothing (we’ll have more to say about the addictive nature of slot machines in chapter 3).

What’s the best strategy for this game? The answer depends, of course, on how the letters are being generated (and whether or not you’re really psychic). For example, if each turn is a fifty-fifty coin toss, then it doesn’t matter which key you press—either outcome is equally likely. There’s no predictability in the outcomes, so your decisions can’t affect your cumulative earnings, which will tend to be flat in the long run anyway. You would do just as well or poorly as a goldfish, assuming you could get a goldfish to press “A” or “B” on a waterproof keyboard. Now suppose we change the odds of the game, so that A appears on the screen 75 percent of the time and B appears 25 percent of the time, but each iteration is unrelated to the next so there’s no overall pattern in the sequence of images. How should you play the game in this case? Simple mathematics tells us the answer: assuming that you aren’t told anything about the odds, once you play a few rounds and see that A comes up more frequently than B, you should always press “A” to maximize your cumulative earnings. The odds of making a correct match for A are always greater than the odds of making a correct match for B. That’s the right answer, but that’s not what most people do.

Experimental psychologists have confronted their human subjects with this exact setting since the 1950s.Even though the mathematics behind the best strategy is simple, people still tend to switch between “A” and “B,” deliberately choosing a strategy that will make them less money in the long run than just sticking to “A.” What’s even more interesting is that people press “A” approximately 75 percent of the time and “B” about 25 percent of time; in other words, they match the frequency that A and B show up in the game. To see how robust this pattern was, psychologists changed the probability of A and B in midstream from 75 percent/25 percent to 60 percent/40 percent. Sure enough, most subjects gradually changed their behavior to mimic the frequency of the computer’s random draws. How odd! People deliberately changed their behavior to another less-profitable strategy. But the oddest part about this behavior is that it’s not unique to humans—it’s been documented in primates, pigeons, fish, bees, and ants.

Andrew W. Lo. Adaptive Markets: Financial Evolution at the Speed of Thought (Posición en Kindle1457-1485). Princeton University Press. Edición de Kindle.