May 7 (Bloomberg) — John O’Donoghue, head of equities at Cowen & Co., talks with Bloomberg’s Erik Schatzker about the possible drivers behind yesterday’s selloff in U.S. stocks and the outlook for the market. U.S. stocks tumbled the most in a year as waves of computerized trading exacerbated a selloff triggered by Europe’s debt crisis, sparking a slide in Asian shares. (Source: Bloomberg)