Saturday, 29 April 2017

Psychological Biases

Loss Aversion

Behavioural finance asserts that investors exhibit loss aversion, that is, they dislike losses more than they like comparable gains.

This results in a strong preference for avoiding losses as opposed to achieving gains.

Advocates of this bias argue that loss aversion is more important to investors than risk aversion,, which is why the "overreaction" anomaly is observed.

While loss aversion can explain the overreaction anomaly, studies have shown that under reactions are just as common as overreactions, which counters the assertions of this bias.


Herding behaviour is a behavioural bias that explains both under reactions and overreactions in financial markets.

Herding occurs when investors ignore their own analysis, and instead make investment decisions in line with the direction of the market.


Overconfdence bias asserts investors have an inflated view of their ability to process new information appropriately.

Overconfident investors are inaccurate when it comes to valuing securities given new information, and therefore stocks will be mispriced if there is an adequate number of such investors in the market.

Evidence has suggested that overconfidence has led to mispricing in most major markets around the world, but the bias has been observed predominantly in higher-growth companies, whose prices are slow to factor in any new information.

Another aspect of this bias is that overconfident investors tend to maintain portfolios that are less-than-optimally diversified because they tend to overestimate their stock-picking abilities.

Information Cascades

An information cascade refers to the transfer of information from market participants who are the first to take investment action upon the release of new information, and whose decisions influence the decisions of others.

Studies have shown that information cascades tend to be greater for stocks when reliable and relevant information about the underlying company is not easily available.


Investors assess probabilities of future outcomes based on how similar they are to the current state.

Mental Accounting

Investors tend to keep track of gains and losses from different investments in separate mental accounts.


Investors are slow to react to changes and continue to maintain their initial views.

Narrow framing

Investors focus on issues in isolation

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