by Charles Cheng, CFA

 

 

In 1979, psychologists Daniel Kahneman and Amos Tversky published a paper called “Prospect Theory” that changed how we think about decision-making. They showed that people don’t always make rational choices, especially when it comes to money and investing. 

Kahneman and Tversky’s work, in addition to subsequent work by Richard Thaler and others, laid the foundation for the field of behavioral finance, which explains why people don’t always make rational economic decisions and how psychology affects investing decisions. The latter point is a struggle that most of us go through on our investing journey. 

For the most part, neither professional nor individual investors are immune to behavioral biases that can undermine their investment decisions, or at least make them more difficult to follow through with.  Once we define these behavioral traps, we can start to find solutions to counteract them.  Here are some examples:

1979年，心理學家丹尼爾·卡內曼（Daniel Kahneman）和阿莫斯·特沃斯基（Amos Tversky）發表了一篇名為“前景理論”（Prospect Theory）的論文，改變了我們對決策的看法。　他們證明，人們不總是做出理性的選擇，尤其是在金錢和投資方面。　

卡內曼和特沃斯基的工作，以及後來理查德·泰勒（Richard Thaler）等人的工作，奠定了行為金融學的基礎。　行為金融學解釋了為什麼人們不總是做出理性的經濟決策，以及心理學如何影響投資決策。　後者是大多數人在投資旅途中面臨的困擾。　

不論是專業投資者還是個人投資者，大多數人都無法避免行為偏差，這些偏差可能會破壞投資決策，或者至少使其更難以堅持。　一旦我們定義了這些行為陷阱，我們就可以開始尋找解決方案來抵消它們。　以下是一些例子：

 

Not selling an investment when you know you should

Prospect theory describes how individuals value gains and losses differently. Because of loss aversion, many investors exhibit a strong preference for avoiding losses rather than acquiring equivalent gains. For example, people feel the pain of losing $100 much more strongly than the joy of winning $100. This can lead investors to hold onto losing stocks for too long, hoping they’ll bounce back, instead of cutting their losses.

Similarly, regret aversion makes investors hesitant to sell losing investments because they fear feeling regret over making a wrong decision.  Also, the endowment effect, which describes how people tend to value things more highly simply because they own them, can lead investors to hold onto stocks longer than they should because they feel a personal attachment.

不賣出投資，即使你知道你應該賣出

前景理論描述了個體如何對收益和虧損有不同的評價。　由於虧損厭惡，許多投資者表現出強烈的偏好，即避免損失而不是獲得相等的收益。　例如，人們對於損失100美元的痛苦感覺遠遠超過贏得100美元的喜悅感覺。　這可能導致投資者過長時間地持有虧損股票，希望它們能夠反彈，而不是及時止損。　

同樣，遺憾厭惡使投資者在出售虧損投資時猶豫不決，因為他們害怕為錯誤的決定感到遺憾。　此外，所有權效應（endowment effect）描述了人們如何僅僅因為擁有某件東西就對其評價更高，這可能導致投資者比應該持有的時間更長地持有股票，因為他們感受到了一種個人情感的依戀。　

 

Selling winners too quickly

The disposition effect refers to the tendency of investors to sell winning investments too quickly in addition to holding onto losing ones for too long. Selling too quickly could cause one to give up significant gains from holding a company with strong growth prospects and competitive moat.

過早賣出盈利股票

處置效應（disposition effect）是指投資者過早賣出贏利投資的傾向，同時又過長時間地持有虧損投資。　過早賣出可能導致投資者錯失了持有具有強大成長前景和競爭優勢的公司所帶來的顯著收益。　

 

Not making investments, even though opportunity costs can be more costly than portfolio losses in the long run

According to prospect theory, for risky choices leading to gains, people tend to be more risk averse than for risky choices to try to avoid losses.  This cautious approach can prevent them from taking advantage of profitable opportunities. For instance, if an investor keeps their money in cash instead of being in the market, they may miss out on significant compounded returns over time. By focusing too much on avoiding risks, they may overlook the greater risk of not investing at all, which can be much more costly to their financial objectives.

 不進行投資，即使機會成本可能比長期的投資損失更高

根據前景理論，當面臨風險選擇可能帶來收益時，人們往往會更加厭惡風險；而當面臨風險選擇試圖避免損失時，人們往往會更加冒險。　這種謹慎的方法可能會阻止他們利用有利可圖的機會。　例如，如果投資者將錢留在現金中而不是投資於市場，他們可能會錯失長期的複利收益。　過於關注避免風險，可能會忽略不投資的更大風險，這可能會對他們的財務目標造成更大的損害。　

 

Following the crowd instead of doing independent research

Herding behavior is where individuals follow the actions of others rather than making independent decisions. While collectively, this can lead to bubbles and crashes, on the individual level, on a personal level, this can have an even more direct impact of keeping someone from buying an investment until after it has made huge gains, and their fear of missing out causes them to buy at the peak.

跟隨群眾而不是進行獨立研究

群羊行為（herding behavior）是指個體跟隨他人的行動而不是做出獨立的決定。　雖然從集體上來看，這可能會導致市場泡沫和崩潰，但在個人層面上，這種行為可能會對個人的投資決策產生更直接的影響。　例如，當某個投資項目已經取得了巨大的收益時，跟隨群眾的投資者可能會因為害怕錯失機會而在高位買入，這可能會導致他們在投資中遭受損失。　

 

Overconfidence in one’s ability to predict market movements

When investors make money following an investment decision, they may automatically assume it was because their research or thesis was correct, even if it was due to unrelated market fluctuations that could only go in one of two directions. Overconfidence is linked to hindsight bias and confirmation bias, where people overestimate their ability to have predicted an outcome after the fact. This may cause investors to put too much money towards strategies that don’t have repeatable outcomes.

過度自信於自我預測市場走勢的能力

當投資者因某一投資決策而賺錢時，他們可能自動認為這是因為自己的研究或論點是正確的，即便這是由於與市場波動無關的因素所致，而這些波動只能朝兩個方向之一發展。　過度過度自信與事後偏見和確認偏誤有關，即人們往往高估自己事後預測結果的能力。　這可能會導致投資者投入過多的資金到那些沒有可重複性結果的策略中。　

 

So, what can we do to defeat these biases?  Here are some steps you can take:

那麼，我們如何克服這些偏見呢？以下是一些你可以採取的步驟：

 

1. Set your strategies in advance

Strategies are repeatable processes that you implement to make profitable investment decisions. Whether your strategy is long term or short term, fundamental or quantitative, you should know the criteria under which you would buy and sell a security. This could be mechanical, like a target price or stop loss, or qualitative, like holding as long as an investment thesis remained valid. Without writing down these criteria before even starting the trade, it would be too easy or tempting to constantly change them on the fly to justify your decision or actions after the fact and be vulnerable to behavioral traps. The process of writing will also clarify whether your strategy is based on objective independent analysis or whether you are following the herd.

1. 事先設定你的投資策略

投資策略是你用來做出盈利投資決策的可重複過程。　無論你的策略是長期還是短期，基本面還是量化，你都應該知道你會在什麼情況下買入和賣出一種證券。　這可能是機械性的，例如目標價格或止損價格，或者是質性的，例如只要投資論點仍然有效就持有。　沒有在交易開始前寫下這些標準，你很容易在事後改變它們來為自己的決定辯護，從而陷入行為陷阱。　寫下這些標準的過程也會澄清你的策略是否基於客觀的獨立分析，還是隨波逐流。　

 

2. Check each investment decision against your stated strategy.

If you have written down these criteria in advance, then you should always check your decisions against them to prevent strategy drift. Doing so, however, requires discipline. For example, if your original target price was +50% over the purchase price based on your research and financial model, there might come a time that you feel that it is time to sell when the stock has gone up only +20%.  It would be extra work and a slower process to justify the new target price based on new information and updating the model, but without doing it, you could start to make decisions according to biases rather than an objective process.

2.將每個投資決策與您的既定策略對照

如果您提前寫下這些標準，那麼每次決策都應與之對照以防止策略漂移。　這樣做需要紀律。　例如，如果您的原始目標價格是比購買價格高50%，根據您的研究和財務模型，那麼當股票僅上漲20%時，您可能會覺得是時候賣出。　然而，不對這一新目標價格重新進行新的信息和模型更新的論證，您可能會根據偏見，而不是根據客觀過程做決策。　

 

3. Evaluate your decisions after the fact

Regular evaluations of your actions are helpful to keep yourself accountable. Did you in fact make your investment decisions based on your stated strategy and criteria?  Are you, investment rationales consistent with your beliefs about investing? (I.e. whether or not it is profitable to make trades based on price action). If not, then you may need to change something in your process to make everything internally consistent.

3.事後評估您的決策

定期評估自己的行動有助於保持自我問責。　你是否真的根據既定策略和標準做出了投資決策？你的投資理由是否與你的投資觀一致？（例如，根據價格行動進行交易是否是有利可圖的）。　如果不是，那麼你可能需要改變你的過程中的某些東西，以使一切內部一致。　

As investors and as people, we may never be fully immune from behavioral biases. But by recognizing and actively tackling these influences, we can improve our decision-making and strive for better and more consistent investment results.

 

作為投資者和人，我們可能永遠無法完全免受行為偏見的影響。　但是，通過認識和積極應對這些影響，我們可以改善自己的決策，努力實現更好、更一致的投資結果。　

 

 

This article reflects the personal views of the author and not any firm’s and should not be viewed as an investment recommendation.

 

 

 

 

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