要投资成功，必须摆脱这项本能的束缚

想象一下：在NBA总决赛上，克里夫兰骑士队的勒布朗·詹姆斯刚刚进了一个跳投。然后他又进了一个。又一个。

三投三中，他手感真棒，接下来这球也跑不了，对吧？

大多数人都会毫不犹豫地回答：“对”。但人们的判断其实和小皇帝的技术没什么关系，更多来自大脑的猜测。看似一个简单的预期，其实是长期进化的结果。不过这种预感最大的问题就是准确度不高。从统计数据看，勒布朗投进的可能性并不比打到篮筐弹出去的可能性大多少，跟之前是否连续进球没什么关系。

这种不假思索就得出结论的现象叫做“近因效应”，深藏在我们的情感脉络中。杜克大学行为经济学教授、《可预测的非理性》（Predictably Irrational）等书作者（也是最早提出上述投篮类比的人）丹·艾瑞里说：“这种效应很有趣。人们总是看最新的证据，过于当真，而且预计后面会发生同样的事。”

“近因效应”在进化上有优势。回想人类祖先在非洲大草原上的生活：如果某个水源点连续几天都有角马出没，很有可能人们会继续去那打猎。如今我们坐在计算机前不用再外出打猎，却仍然本能地在最近发生的事件中寻找规律，较久远的记忆对我们行为的影响则较小。

当然了，问题在于角马并不会总在同一地点出现。所以近因效应对投资者来说很特别危险，一个不留神就会变成为人们大脑中错估投资方向的罪魁祸首。理智上，我们都知道本世纪已经出现了两次大熊市，分别是在2000-2002年和2007-2009年。然而今年3月，现代史上持续时间第二长的牛市即将进入第八个年头，近因效应可能会给我们一种虚假的安全感，特别是看到过去三、四年非常高的回报以后。艾瑞里指出：“想想资产泡沫形成的过程就会发现，情况往往如此。市场上涨再上涨，我们就开始认为会一直涨下去。”

市场专业人士也难免受这种思维方式影响。2008年初，全球经济乍现疲软之势。但在连续五年实现正回报以后，股票分析师的信心也升至历史高点。研究机构Bespoke Investment Group最近的研究显示，当时华尔街一致认为市场还能上涨11.1%。大家应该想到了，分析师的预测主要依据也是近期行情。我们也都知道接下来发生了什么——经济断崖式下跌，当年标普500指数跌去了38.5%。

近因效应还有助于解释贪婪或恐慌行情中散户的行为。投资研究公司TrimTabs Investment Research首席执行官大卫•桑茨奇指出，资产流入经常出现在股市就要见顶时，流出则经常出现在市场底部，正好跟投资者应该采取的操作相反。最近的情况就让人感觉不妙——基金研究机构晨星的数据显示，去年12月流入美国股票共同基金的资金达278亿美元，是2000年4月科技股临近崩盘以来月度流入最高记录。

行为经济学家、加州大学洛杉矶分校教授什洛莫·本纳茨认为，快要退休的投资者特别容易受近因效应的影响，然而临近退休正是最亏不起大把钱的时候。这是衰老应对机制的一部分——如果一生中总是接连不顺，感到无能为力，人们就会失去生活的勇气。但往往牛市接近尾声时投资者的决策最容易过度乐观，承担巨大的风险。

对于未来，估计专家也算不准熊市什么时候来——话说回来，确认没人说对过。那么，我们怎样才能抵御并削弱近因效应的影响，不让过于乐观（同样的，过于悲观）的倾向对决策产生不利影响呢？初学者可以让证券投资进入“自动驾驶”模式，剔除情绪波动因素。目标日期基金或许是个选择，这种基金会自动调整投资配置，随着持有人年龄的增长降低投资风险。Betterment和Wealthfront等智能投顾机构也能帮上，只要提前设置好就能在某类资产的价格达到不正常水平时自动让证券投资重新回归平衡。多伦多大学行为经济学家丽莎·克雷默说：“我热爱所有阻止人们冲动决定的投资方法。”

历史数据也是决策时值得考虑的因素。摩根大通资产管理指出，牛市平均长度为54个月，比截至今年1月的奥巴马-特朗普行情短41个月。标普500指数的长期平均市盈率呢？只有15倍，而目前的市盈率已经超过25倍。这些长期指标表明，要维持目前的估值和市场的良好表现并不容易。

正因为如此，如果市场下跌，一定要确保所有操作都是根据长期计划，而不是CNBC最新报道传播的情绪。主要指数不断破记录的时候就是投资者进行调整的良机。如果总投资中股票的比重已经从60%的目标值一路上升，已经达到比方说75%，可以卖掉一部分股票锁定利润，把资金投入市场滑坡时较为坚挺的资产，比如投资级债券。年纪大一些的投资者可以把资金转移到风险更小的资产中，比如现金或年金。

Fuller & Thaler Asset Management研究主管拉斐·吉欧凡纳佐认为：“投资时千万不能跟着情绪走，就像希腊神话中驾船穿过塞壬海妖歌声的奥德修斯一样。用蜡堵住耳朵，把自己绑在桅杆上，否则只能眼睁睁跟着市场一泻千里。”

怎样克服既有思维定势

包括“近因效应”在内，根深蒂固的思维习惯可能影响投资者的决策，导致投资蒙受损失。以下三种方法可以尽量克服。

价格高时要当心

如果价格/市盈率高得离谱，经常意味着股票上涨时间有些过长。目前股票价格已经远高于平均水平，或许是个卖出大涨股落袋为安的好机会。

为了退休安全操作

退休前后几年是投资损失对长期计划影响最严重的时候。处在这个阶段的人应该考虑把资金更多地配置在现金和债券上，不管感觉市场有多牛。

依靠“自动驾驶”

在兴奋状态下，阻止冲动型买卖的工具会很有用。目标日期基金、“智能投顾”以及年金都可以帮助投资者避免在牛市中冒太多风险，或者在熊市中恐慌抛售。

作者：Chris Taylor

译者：Charlie

审校：夏林

Picture this: It’s the NBA Finals, and LeBron James has just drained a jump shot for the Cleveland Cavaliers. Then he hits another. And another.

He’s on a hot streak: three in a row. He’s going to hit the next one, right?

Most people would unhesitatingly reply, “Yes.” That assumption doesn’t say as much about King James’s skills as it does about the inner workings of your own brain. Indeed, a whole lot of evolutionary history is packed into that projection. But here’s the thing about that hunch: It’s off the mark. Statistically, LeBron isn’t significantly more likely to make the shot than he is to clang it off the back rim—streak or no streak.

This leaping-to-conclusions phenomenon is called “recency bias,” and it’s deep in our emotional wiring. “It’s an interesting effect,” says Dan Ariely, a professor of behavioral economics at Duke University and the author of books including Predictably Irrational (and the originator of the hoops analogy). “We look at the most recent evidence, take it too seriously, and expect that things will continue in that way.”

There’s an evolutionary advantage to this. Think back to the origins of humanity somewhere on the African savannas: If the wildebeests have shown up at the same watering hole a few days in a row, odds are we’re going to hunt at that same spot the next day. Nowadays, though we’re hunched at computers instead of hunting game, we still instinctively seek patterns in the events that have happened most recently, while memories of older occurrences have less influence over our behavior.

The problem, of course, is that the wildebeests don’t always come back. And that makes recency bias particularly dangerous for investors: Unchecked, it’s your brain’s very own portfolio killer. Intellectually, we know that the market already saw two brutal bear markets this century—in 2000–02 and 2007–09. But as we approach the eighth birthday in March of the second-¬longest bull market in modern times, recency bias can lull us into a false sense of security, especially given the very good returns of the past three or four years. “If you think about the creation of asset bubbles, that’s always what happens,” Ariely says. “Things go up and up and up, and we start thinking it has to always go up.”

Market professionals are hardly immune to this trend. At the beginning of 2008, trouble signs were emerging in the global economy. But after five straight years of positive returns, sentiment among equity analysts neared an all-time high, with the Wall Street consensus calling for an 11.1% gain, according to a recent study by Bespoke Investment Group. Their calls were based in part on—you guessed it—analysis of the recent past. We all know what happened next: The economy went off a cliff, and the S&P 500 fell 38.5% that year.

Recency bias also helps explain retail investor behavior during times of greed or panic. Assets often flow into stocks near market tops and exit at the bottom—exactly the opposite of what investors should be doing, says David Santschi, CEO of TrimTabs Investment Research. Recent signs here aren’t encouraging: Net inflows for U.S. stock mutual funds hit $27.8 billion in December, according to fund research shop Morningstar—the highest monthly total since April 2000, at the dawn of the tech-stock crash.

Investors can be particularly susceptible to recency bias as they get closer to retirement—¬exactly the time when they can least afford big losses. That’s part of the mechanism of coping with aging, according to Shlomo Benartzi, a behavioral economist and UCLA professor. If we felt constantly hamstrung by the bad things that have happened to us over the course of our lives, none of us would get out of bed. But those rose-tinted glasses can cloud investing decisions, leading savers to assume too much risk at the tail end of a bull market.

Looking ahead, few experts are predicting the imminent arrival of a bear market—then again, few ever do. So how can you combat and counteract your own recency bias and resist letting excessive optimism (or pessimism, for that matter) hurt your decision-making? For starters, you could put your portfolio on autopilot, taking your mood swings out of the equation. That might mean vehicles like target-date funds, which shift investment allocations automatically to make them less risky as the account holder ages. Also helpful: robo-advisers such as Betterment and Wealthfront, which can be set up to rebalance your portfolio automatically when the prices of one asset class get out of whack. “I’m a big fan of any investing approach that removes us from impulse-based decisions,” says Lisa Kramer, a behavioral economist at the University of Toronto.

It’s also worth keeping historical data in your decision-making arsenal. The average bull-market length is 54 months, according to J.P. Morgan Asset Management—41 months shorter than the Obama-Trump bull run, through January. And the S&P 500 long-term average price/earnings ratio? It’s just 15, compared with more than 25 today. That kind of wider context signals that today’s valuations and recent good times won’t be easy to sustain.

All the more reason to make sure that, if and when the market does turn, any moves you make will be driven by a long-term plan rather than the emotions generated by the last thing you heard on CNBC. With major indexes setting records, it’s a good time for investors to rebalance: If the equities portion of your portfolio has ballooned from your 60% target to 75%, say, take some profits off the table and use them to buy asset classes that are hardier during downturns, like investment-grade bonds. Older investors may want to move that money into assets that are even less risky, like cash or annuities.

“In investing you have to deny your emotions, like Odysseus sailing by the sirens in Greek mythology,” says Raife Giovin¬azzo, research director at Fuller & Thaler Asset Management. “Put wax in your ears or tie yourself to the mast—otherwise, you’re going to drown along the cliffs.”

How to Beat Your Biases

Deep-rooted mental habits, including “recency bias,” can throw off investors’ decision-making and hurt their portfolios. Here are three ways to keep those habits in check.

Watch out for high prices

Unusually high price/earnings valuations are often a sign that the party for stocks has gone on a little too long. With stocks trading well above their averages, now may be a good time to sell big winners and put the profits aside.

Play it safe for retirement

The years immediately before and after retirement are when losses can hurt an investor’s long-term plans the most. Savers in that life stage should consider putting more money in cash and bonds—no matter how bullish they feel.

Rely on an autopilot

When emotions run high, it helps to have tools that discourage buying or selling on impulse. Target-date funds, “robo-advisers,” and annuities can help investors avoid taking excessive risks in good times or panic selling in bad.