It's been a volatile week on the stock market, and it looks like the bear may have just come out to play. Analysts have confirmed that a head and shoulders top pattern has formed on the S&P 500. This pattern is considered very bearish and is likely to cause the index to drop over the coming days. A head and shoulders pattern is characterized by three distinct movements in price, with the peak in the middle signifying the top of the trend. When the first peak is higher than the second peak, it signals that the market is reversing and heading downwards. The head and shoulders pattern has been forming on the S&P 500 since April of this year. After the index peaked for a second time at the end of May it appears the market is finally ready to move downwards. This downward movement will be a test for the stability of the market going forward. After this long bull run, investors may be hesitant to buy in when they see the market reversing. If the index can stay supported despite this bearish pattern, then investors may feel more confident in investing and the markets are likely to recover. However, if the market proves to be weak in the face of this bearish pattern, it may indicate that the long bull run is over and that investors should expect even more volatility in the coming weeks. In either case, investors should pay close attention to the S&P 500 to guide their trading decisions. If the markets start to decline, then it's a signal that it may be time to start selling off some of your riskier holdings. On the other hand, if the index levels off or maintains its upward trajectory, then it may be a good opportunity to enter the market and buy.