The Economist has a good write-up on the work of experimental economist John List. As you may know, an endowment effect arises when you value something more, simply because you own it. In the context of laboratory experiments, often people will value a coffee mug more, much more (say five times more), once someone gives them the mug as theirs. In contrast, economic theory suggests that your willingness to pay for the mug should only be slightly less than your willingness to give up the mug for money (willingness to be paid). Here is a piece by recent Nobel Laureate Daniel Kahneman on the same topic.
List had the ingenious idea to see which traders were most subject to this ownership bias. So he took people who traded sporting cards and gave them other sporting memorabilia. The key result is this: the more real world trading experience a person had, the weaker the ownership or endowment effect. Professional dealers hardly seemed to be biased at all. The lesson is simple: asset markets work well when traders have the necessary experience. List also showed that sellers learn how to trade properly, without much of a bias, more rapidly than buyers do, which may explain why neophyte buyers get taken advantage of in stock markets, and why upward-moving bubbles may start. (Researchers have found that other distinctions may matter as well, you may value the mug more if you won it in a tough competition, as opposed to receiving it as a gift.)