The traditional rules of investing are not working in the current market conditions, according to Jacob De Tusch Lec, who runs the £3.8bn Artemis Global Income fund.
He said the ending of quantitative easing in the US and generally higher interest rates have created some of the messiest, least-predictable market conditions for years.
He said the rules that applied during the long period of near-zero interest rates and quantitative easing are being re-written on the hoof.
Mr De Tusch Lec said: "For a long time, investors had a 'playbook' – a number of rough-and-ready rules of thumb suggesting how to respond to a given change in the economy or monetary policy. That playbook is now being ripped up.
"Given the complexity of the plumbing that underpins the financial system, it should not be surprising that the end of a decade of unconventional monetary policy is having complex, unpredictable effects.
"Investors are looking at various indicators to see if the plumbing is still working."
He said he is responding to these changes by buying no more US stocks and considering buying more shares with defensive characteristics.
The fund manager said while some of the rules that apply when interest rates rise, such as poor performance from stocks in areas such as utilities and consumer shares, has happened, he has been left puzzled by the poor returns from earlier stage technology companies and banks.
He said earlier stage technology companies and banks are supposed to do well when interest rates are rising, but have not proved to be more defensive during the recent period of market turbulence.
Mr De Tusch Lec said he had been avoiding investments in the biggest technology companies (known as the Faangs) because he felt in a period of market turbulence it would be the shares that have performed best that would fall.
But the performance of his fund, which has lost 6.5 per cent in the past three months, has been hit by a sell-off of other technology shares, and banks.
He said despite the modest valuations at which US bank shares are trading, they have not proved to be the defensive investment he had expected.
Higher interest rates are supposed to be good for banks, as the higher bond yields are supposed to mean more profits for banks.
Meanwhile, interest rates rising should be a sign that economic growth is improving, which should also boost the returns from banks.
Mr De Tusch Lec said the global economy is still growing but the pace of growth has slowed, while the stock market is now moving to a "risk-off" phase, whereby bond yields will remain low and equity markets perform poorly.
Bruce Stout, who runs the £1.6bn Murray International investment trust, said: "Rising market volatility, concerns over stretched valuations and increasing risk aversion combined to send the majority of stock markets lower whilst simultaneously pushing sovereign bond prices higher.