This means that what you notice or find in most situations depends on the things that you have deliberately chosen to search for or pay attention to. For example, someone may look for evidence that a certain political party is doing something wrong and find it, but someone else may look for evidence that the party is doing something right and find that instead. Similarly, someone may be listening for evidence of wrongdoing and hear it, while another person who is listening for evidence of progress might hear that instead.