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'Humans, bees share risk-taking mechanism'

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midastouch017   Friday, 06/13/08 07:09:18 AM
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'Humans, bees share risk-taking mechanism'
By JUDY SIEGEL-ITZKOVICH

When presented with the chance for a big reward from a risky endeavor, people and honeybees use the same mechanism to decide, according to researchers at the Technion-Israel Institute of Technology, Tel Aviv University and the Hebrew University. Their research on "perceptual accuracy and conflicting effects of certainty on risk-taking behavior" has just been published in the prestigious journal Nature.

The researchers discovered that people are more prepared to gamble on risky action rather when the differences between the various possible outcomes are well defined. However, if the different outcomes are hard to distinguish, they are much more likely to select a safe option, even if the probability of the risky choice failing has not changed at all.

The findings are relevant to how people decide to invest in the stock market, how to gamble, whom to marry, where to work, whether to remain honest or commit crimes, and to many other life decisions.

Profs. Ido Erev of the Technion's industrial engineering and management faculty, Arnon Lotem of TAU, Sharoni Shafir of HU's agricultural, food and environmental quality sciences faculty and their colleagues wanted to understand the "certainty effect" and the "reversed certainty effect" that in previous studies showed opposite tendencies in humans and rats.

Sometimes people are no smarter in their decision-making than rats. At least, so it seemed from a paper shown to Lotem, a zoologist, by his colleague and co-author, Erev, an industrial engineer. Lotem wondered why this might be.

The paper reported on the "certainty effect," which refers to the tendency for people to select the safer of two prospects when it provides a good and certain outcome. The "reversed certainty effect" refers to the reduced tendency to prefer the safer option when this prospect is associated with certainty. The researchers managed to restore the certainty effect in experiments on both humans - 50 undergraduates offered money for making choices in the form of a cluster of red dots or numerical digits on a computer screen - and honeybees offered sugar solutions of different concentrations.

In previous research, when rats were repeatedly faced with the option of receiving either a bigger reward infrequently or a smaller reward with certainty, they preferred the safer option - even though it was less profitable on average. Thus the insects behaved like people did when the payoff odds of choosing two alternatives are described to them verbally.

However, Erev's group had found that if humans are faced with the same situation as the rats - that is, the pay-off probabilities are not explained to them - they behave differently. On a "computerized money machine," people repeatedly display the "reverse certainty effect" by gravitating toward the bigger payoff, even though it is statistically less likely. The research team decided to find out what hid behind this difference in behavior. They discovered that both humans and other animals can exhibit certainty or reverse certainty depending on the cues available to them.

Because humans can perceive the precise amount of a reward from reading numbers, while rats must rely on their senses to make estimates, the researchers suspected that perceptual accuracy was the key to solving this paradox. They started by devising a series of experimental scenarios that manipulate the clarity of reward cues, and then tried them out on both honeybees and humans.

In one experiment, the student volunteers had a choice of two computer buttons, one marked 'R' (for risky) and the other marked 'S' (for safe). Pushing S resulted in a payoff of three points with absolute certainty, while pushing R resulted to a payoff of four points in eight out of 10 tries. But the students did not know what the letters stood for and learned about how likely they were to earn the rewards only by trial and error as they flashed on screen.

Watching people push buttons seemingly at random was enlightening, Lotem said. "In theory, people could have been very smart and pressed one button 20 times and pressed another button 20 times, and, like a scientist, figured out the average. But people don't behave like statisticians."

Instead, subjects tried both buttons and developed a preference for the button perceived as better "most of the time." However, when payoffs were represented by the visual display of scattered dots rather than through clear numerical means, making it more difficult to tell which was better, people preferred the safer button. In other words, they exhibited the certainty effect, like the rats in the study that first piqued Lotem's interest.

In the other part of the experiment, the honeybees that were rewarded with sugary solutions of varying concentration surprisingly behaved like people, preferring the risky option when discrimination between rewards was easy, and the safe option when discrimination was difficult.

"Honeybees can't count," noted Lotem. "But, if you give them a high concentration of sugar or if they get none, they remember."

Like humans, the bees behaved as though they preferred the option perceived as better most of the time.

They concluded from their research that people and bees use the same decision-making mechanism and make the same mistakes when they have to decide between a sure reward and a bigger, but riskier reward.

Lotem and his colleagues wondered how their findings might apply to real-world situations.

"In the real world, rewards may frequently be ambiguous, and you never know when conditions are going to change," said Lotem. "So perhaps the tendency to explore both options and to prefer the one perceived as better most of the time is a good strategy."


http://www.jpost.com/servlet/Satellite?cid=1212659715349&pagename=JPost%2FJPArticle%2FShowFull


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