Why do people turn to economists for forecasts, even though they are hopeless forecasters? Illustration: Ron Tandberg It commissioned the Queensland behavioural economics group at the Queensland University of Technology Business School to conduct some experiments. The group assembled a lot of business-school uni students and gave each of them 100 units to be notional invested in a portfolio of bonds, hybrids and shares, getting them to take it seriously by promising to let them keep any profit they made. First, however, it asked each student a bunch of questions designed to establish whether their decision-making was influenced any of a range of "cognitive biases" rather than solely rational consideration of the options. Investors are known to be commonly affected by such "heuristics" (mental shortcuts) as the availability bias, representativeness bias, framing bias, recency bias, overconfidence, illusion of control, competence bias, ambiguity aversion and mental accounting. So now, gentle reader, it's time for me to ask you some strange questions on this long weekend.

Give me high and low estimates for the average weight of an adult male sperm whale (the largest of the toothed whales) in tonnes. Choose numbers far enough apart to be 90 per cent certain that the true answer lies somewhere between. Don't like that one? Try this: give me high and low estimates of the distance to the moon in kilometres. Choose numbers far enough apart to be certain that the true answer lies somewhere between. Now something more personal. When you buy a Lotto ticket do you feel more encouraged regarding your chances if you choose the number yourself rather than using a computer-generated number? Answer: (a) I'm more likely to win if I control the numbers picked, or (b) it makes no difference to me how the numbers are chosen. Huh? What's all this about? Extensive testing has allowed psychologists to use people's answers to the first two questions to determine whether they suffer from overconfidence. (If you must know, such whales weigh about 40 tonnes and the moon is 384,400 kilometres away.)

Plenty of investors are overconfident in the sense that they have unwarranted faith in their own intuitive reasoning, judgments and cognitive abilities. Their ability sell up just before the boom turns to bust, for instance. Can you guess what the Lotto question was intended to discover? It makes no difference to your (tiny) odds of winning Lotto whether you or a computer picks your numbers. If you imagine it does, you're suffering from what psychologists call the "illusion of control" – the belief you can control, or at least influence future outcomes when, in fact, you can't. The illusion of control has been found to contribute to the overconfidence bias. And it's a lot more common than you may think. It is, for instance, the reason people keep asking economists for their forecasts about the economy even though they know economists are hopeless forecasters. We like to delude ourselves we can control the future. Anyway, the Queensland behavioural economists – Anup Basu, Uwe Dulleck, Yola Engler and Markus Schaffner – found from their experiment that students who were more overconfident and suffered from the illusion of control were more inclined than others to invest in hybrid securities.

With better information about what it is that attracts some investors to buy hybrids, the commission should be able craft more effective warnings to people who need to think a lot more carefully before they leap in. Of course, it also helps to know how to word your warnings. A growing number of government regulatory bodies around the word have found that different ways of writing a letter can have a surprising effect on the way people respond to it – whether they ignore it or act on it. The commission asked the Queensland behavioural economics group to suggest ways of improving its letters to the directors of companies in liquidation, reminding them of their legal duty to co-operate with the liquidator in handing over the company's books and providing any other information. Again the group conducted a laboratory experiment. Such experiments, using uni students, have their disadvantages, but they also have the advantage of giving researchers greater ability to control the many factors that could influence the decisions you're studying. The experimenters recommended that the commission proceed to a randomised controlled trial where some directors were sent the present letter, while others were sent one of four different letters: one where the order of the points was reverse to make them easier to remember, one including a "social norm" noting that about 75 per cent of directors comply, one that allows directors to make active decisions that involve them in the process, and one that appeals to the good intentions most directors have.

At least some of those changes are likely to significantly improve directors' compliance. Practical regulators are getting much more useful advice from the behavioural brand of economists. Ross Gittins is the economics editor. Twitter: @1RossGittins