We like ideas more when we are the ones who came up with them. This is not an easy tendency to test, but Ariely came up with an experiment that got participants to actually think they came up with an idea that he planted. When participants thought they had come up with an idea themselves, they gave the idea higher ratings.
This tendency may serve a useful purpose. It may give us a high level of commitment to our ideas, giving us the power to follow through and carry our ideas to the max. But the dark side is that we close our minds to better ideas, simply because we did not come up with them ourselves. Companies can fall into this trap as well, as many accept internally generated ideas as more useful than those from other, more successful companies.