How Market Volatility Affects Our Brains

How Market Volatility Affects Our Brains

September 2, 2015 $vxx, Behavioral Finance, Tactical Asset Allocation Research
Print Friendly
(Last Updated On: September 22, 2015)

The current market volatility is justifiably causing people stress. Nobody wants to see their hard-earned wealth get vaporized.

But how does increased stress affect decision-making?

A recent paper published in the Proceedings of the National Academy of Sciences highlights an interesting finding:

  • Humans don’t have stable risk preferences–stress makes us more risk-averse.

In, “Cortisol Shifts Financial Risk Preferences,” the authors question a core assumption in economic models that “agents” (i.e., human beings) have stable risk preferences. They find via experiments that this assumption may not be empirically valid. Humans are more afraid of risk when they get stressed–especially sustained stress.

In the figure below, the authors highlight the average utility of their subjects under different conditions. If subjects are more risk-averse, their marginal utility for increased expected payoffs will increase at a decreasing rate. In summary, a flatter curve means more risk aversion.

stress and risk aversion

Why is this relevant?

We think this research ties into the historical effectiveness of trend-following-based risk management systems. We talk about downside protection via trend-following rules and highlight a behavioral hypothesis for why these rules work.

Consider the concept of dynamic risk aversion, which is the idea that human beings don’t stick to a set risk/reward behavior—their appetite for risk can change depending on their recent experience… As market prices drop below the twenty percent threshold, an economist assumes that the new price is a bargain. Expected returns have gone up after prices have moved down, while volatility and risk aversion are assumed to be relatively constant

But this doesn’t happen. Stocks can—and have—gone down over fifty percent, and these movements are much more volatile than the underlying dividends and cash flows of the stocks they represent! Remember 2008/2009? How many investors swooped in to buy value versus threw the baby out with the bathwater and kept selling? …

One approach to understanding this puzzle is by challenging the assumption that investors maintain a constant aversion to risk. Consider the possibility that investors change their view on risk after a steep drawdown (i.e., they just lived through an earthquake). Even though expected returns go up dramatically, risk aversion shoots up dramatically as well.

This paper’s evidence supports our behavioral hypothesis that trend rules work because humans get more risk averse when markets start dropping and volatility gets wild. The research also highlights that one-off stress events won’t drive dynamic risk aversion–we need a sustained period of stress and chaos to change hearts and minds. The recent turmoil in August–and now into September–may not be enough sustained stress to change minds, but if the drama continues…watch out!


Note: This site provides NO information on our value investing ETFs or our momentum investing ETFs. Please refer to this site.

Join thousands of other readers and subscribe to our blog.

Please remember that past performance is not an indicator of future results. Please read our full disclosures. The views and opinions expressed herein are those of the author and do not necessarily reflect the views of Alpha Architect, its affiliates or its employees. This material has been provided to you solely for information and educational purposes and does not constitute an offer or solicitation of an offer or any advice or recommendation to purchase any securities or other financial instruments and may not be construed as such. The factual information set forth herein has been obtained or derived from sources believed by the author and Alpha Architect to be reliable but it is not necessarily all-inclusive and is not guaranteed as to its accuracy and is not to be regarded as a representation or warranty, express or implied, as to the information’s accuracy or completeness, nor should the attached information serve as the basis of any investment decision. No part of this material may be reproduced in any form, or referred to in any other publication, without express written permission from Alpha Architect.

Definitions of common statistics used in our analysis are available here (towards the bottom)

About the Author

Wesley R. Gray, Ph.D.

After serving as a Captain in the United States Marine Corps, Dr. Gray earned a PhD, and worked as a finance professor at Drexel University. Dr. Gray’s interest in bridging the research gap between academia and industry led him to found Alpha Architect, an asset management that delivers affordable active exposures for tax-sensitive investors. Dr. Gray has published four books and a number of academic articles. Wes is a regular contributor to multiple industry outlets, to include the following: Wall Street Journal, Forbes,, and the CFA Institute. Dr. Gray earned an MBA and a PhD in finance from the University of Chicago and graduated magna cum laude with a BS from The Wharton School of the University of Pennsylvania.