You can switch lines all you want in the grocery store, but it doesn’t mean you’ll actually save any time. Harvard Business School researchers say people standing at the back of the line are 20 percent less satisfied than any other person in the line. This phenomenon is called “last place aversion” and it can cause people to make poor decisions, such as switching lines when they are already in the shortest one. Lead researcher Michael Buell says folks in the study who chose to switch lines ended up waiting around ten percent longer, and those who switched twice waited around 67 percent longer. Also, people often switched lines only because they felt bad about being last. If you do get stuck at the end of a line try to wait at least ten seconds before you decide to switch lines, as that is when your “last place aversion” will be strongest.