Art Cashin said there are three factors at play in today's weakness for stocks.
Cashin, UBS' director of floor operations at the NYSE, told CNBC's Mary Thompson around midday that gold's strength "gives you a mild hint that there's at least an undertone of geopolitical concern here."
He also said "strong hints of deflation" are fueling a global "hunt for yield."
Cashin said, "If those momentum stocks start selling again then that's going to say all we just saw was an oversold rebound and nothing more meaningful."
He predicted that if the Nasdaq falls to a support level of 4100-4105, "you should see nervousness spread into the other indicies."
—By CNBC's Alex Crippen. Follow him on Twitter