The VIX is a measure of option volatility, so when it spikes higher--as has happened in the past two trading sessions--it's a sign that market makers are pricing options for further movement. This typically occurs following market declines, which leads to the notion that an elevated VIX reveals trader fear, while a low VIX suggests complacency.
On Friday, the VIX closed 18% above its 20 day average--a substantial spike. Since March, 2003 (N = 804 trading days), we've had 32 occasions in which the VIX has closed 15% or more above its 20 day average. Two days later, SPY has averaged a gain of .58% (21 up, 11 down). That is much stronger than the average two-day gain of .12% (437 up, 367 down) for the sample overall.
This is consistent with Larry Connors' research, which suggests that VIX elevations lead to superior returns in the near term.