EFTA01149271.pdf

NEWS & VIEWS EVOLUTION Selection for positive illusions Everybody knows that overconfidence can be foolhardy. But a study reveals that having an overly positive self-image might confer an evolutionary advantage if the rewards outweigh the risks. SEE LETTER P.317 MATTHIJS VAN VEELEN & MARTIN A. NOWAK sk anyone with a driver's licence to A rate their own abilities behind the wheel, and most people will report that they are above average'. The same is true for self-assessments ofperformance in cogni- tive tasks', ofattractiveness' (by men, not by women) and of the healthiness ofour behav- iour': people typically place themselves higher on the ladder than they really are. In a survey of 1 millionhigh-school students', a solid 70% rated themselves as above-average leaders (versus 2% who thought of themselves as below average), and a spectacular 94% of col- lege professors possess teaching abilities that are above average — according to themselves°. Obviously they cannot all be right, but that does not make them dysfunctional or mentally unhealthy. In fact, one way to get self- assessments to obey some minimal aggregate consistency is to restrict surveys to sufficiently depressed people' (although this finding has Figure I I Float like a butterfly, sting lilce a bee. Muhammad Ali saw himself as"the king of the world". been questioned"). Mentally healthy people His supreme confidence helped him to win many fights. Johnson and Fowler" report that overconfidence blissfully suffer front what are called positive can confer an evolutionary advantage. illusions: they overestimate their abilities, as well as their control over events, and they under- people perceive themselves compared with no-brainer: fight if you are stronger, concede estimate their vulnerability to risk1'. Ofcourse, others". That may lead to a mistake here and if you are weaker. But it gets interestingif the one can overrate oneself too much, as do suf- there, but the benefits of the esteem ofothers contestants have imperfect information about ferers from narcissistic personality disorder or could outweigh that (Fig. 1). each other's strength. In this situation, contest- megalomania, but healthy people's estimates of Johnson and Fowler" suggest a remark- ants might back off because they think their their own abilities seem to start just a little above able alternative explanation. According to opponent is stronger than he or she really is. where they really are. Reporting on page 317 their model, a biased self-belief can actu- A weaker contestant could then win a reward of this issue, Johnson and Fowler" describe a ally lead people to make the right decision, ifshe claims it while the opponent backs off. model that might explain why this is so. whereas an unbiased self-image would lead to This situation can be dealt with within the An obvious question is how overconfidence a suboptimal decision. That sounds counter- realm of what economists call perfect ration- survives the process of natural selection. The intuitive, but the key lies in the authors' depar- ality, which assumes that both parties under- prevalence of rose-tinted self-assessments ture from what could be called the 'naive stand all aspects of their situation, and that suggests that it might even be adaptive to be economist's idea ofhow humans arrive at deci- they correctly anticipate the odds that the overconfident — in contrast to schizophrenia, sions ('naive because many economists are not other player will claim the resource. But John- for instance, which is maladaptive but none- that naive at all). son and Fowler suggest that there is a short cut theless exists in moderate proportions in The authors model envisages a valuable to the right decision. The short cut combines humans. But how can it be adaptive to mis- resource that two individuals can decide to a simple heuristic — fight if you think you're judge how you compare with others? You claim or not. If both claim it, then they will stronger — with a bias.If the resource is valu- would think that an incorrect assessment fight over it — which is costly for both. The able relative to the cost of fighting, then the risk of one's own capabilities can induce only stronger individual will win the fight and gain ofan extra battle here and there is outweighed misguided decisions. access to the resource. If only one of them by the gains made when otherwise unclaimed One suggested explanation is that there is claims the resource, it goes to that person. If resources are won, which makes overestimat- a benefit in having others think that you're neither claims it, no one gets it. ing ones own fighting abilities worthwhile.If great. And as there is no better way ofbeing a Now ifboth contenders could simply assess the cost of fighting is large relative to the value strong persuader than firmly believingin your- the fighting strength of the other with perfect of the resource, then it is better to under- self, this would lead to an upward bias in how accuracy, the optimal strategy would be a estimate ones own strength. The behaviours 282 I NATURE I VOL 477 I 1S SEPTEMBER 2011 EFTA01149271  NEWS & VIEWS RESEARCH described by the authors model are actually which of these two describes us best. 1. Svenson.O.Acta Psycho'. 47, 143-148(1981} more complex than described above, because It would also be interesting to establish a link 2. Krug% J. & Dunning, O.J. Pers. Social Psycho,. 77. 1121-1134(1999} the model also predicts that populations can, between the authors' findings and overconfi- 3. Gabriel M. T., Critelli.J. W.& Ee. J. S. J. Pers. 62. for instance, evolve to a stable mixture ofboth dence in trading behaviour", the willingness to 143-155(1994). over- and under-confident people. buy overly complex financial products (which 4. Hoorens, V. & Harris. P Psycho'. Health 13, 451-466 Another evolutionary explanation is the are thought to have led to the current crisis in (1998). following: overconfidence could reduce aver- the banking system), political decisions that 5. Alicke. M. D. & Govorun, 0. in The Selfin Social Judgment (eds fUkke, M. D.. Dunning. D.0.& age pay-off,but top performers will still come lead to war", and the evolution of fighting Krueger. J.1)85-106 (Psychology. 2005). from the group ofoverconfident individuals. behaviour in animals". Given that 94% ofcol- 6. Cross. P New Directions Higher £doc 17,1-15 For example, overconfidence about roulette- lege professors rate themselves as above aver- (1977). playing 'abilities will lead to overall losses from age, there should be enough overconfidence 7. Taylor. S. EL Brown. J. D. Psychot Butt 103, this game, but the best performers will have around to tackle all the natural follow-up 193-210(1988). 8. Shedler,J. al. Am. Psycho?. 48.1117-1131 played often. Strong selection — as in 'winner questions. ■ (1993). takes all'— should favour overconfidence. 9. Colvin, C. R.& Block. J. Psycho!. Bud. 116, 3-20 Johnson and Fowler's study" prompts a Matthijs van Veelen is at the Center (1994). variety ofinteresting questions. The 'winning for Research in ExperimentalEconomics 10.Sharot, T. The Optimism Bias: A Thor of the strategy' (for low fighting costs) can be wired and Political Decision Making, University Irrationalrosithe Brain (Pantheon, 2011). 11.Johnson, D. D. P.& Fowler.J. H. Nature 477. into the brain in two ways. The first involves ofAmsterdam, Roetersstraat 11, 317-320(2011). a simple heuristic plus overconfidence: only 1018 WE Amsterdam, the Netherlands. 12.Trivers. Ft Deceit and Self-Deception: Fooling Yourself fight when you think you are stronger, but Martin A. Nowak is at the Programfor the Better to Foot Others (Allen Lane. 2011). overestimate your strength. The second way Evolutionary Dynamics, Department of 13.Barber. B. M. & Odean, T. Q. J. Ecoa 116. 261-292 involves perfect rationality without overcon- Mathematics and Department ofOrganismic (2001). 14.Johnson. D. D. P. Overconfidence and War The fidence: given some uncertainty, the winning and Evolutionary Biology, Harvard University. Havoc and Glory of Positive illusions (Harvard Univ. strategy can be to fight opponents even if they Cambridge, Massachusetts 02138, USA. Press. 2004). seem slightly stronger than you. Future empiri- e-mails: cm.vanyeeleneuvairk 15.Enqu al. M.& Leimar.O. J. Them Bid. 127, cal and theoretical studies might help to decide martin_nowakeharvard.edu 187-205(1987} IS SEPTEMBER 2011 I VOL 177 I NATURE 1 283 EFTA01149272