While the $S&P 500 Index (.SPX.US)$ was en route to a 1.4% gain Monday, the $CBOE Volatility S&P 500 Index (.VIX.US)$ — a gauge of cost on options tied to the stock benchmark also known as VIX — jumped more than 2 points to surpass 25. Not only do same-direction moves buck the historical pattern where the two normally move in opposite directions, their outsize jumps today mark the first time since 1997 when both climbed in sync as much as they...