Psychologists divide interference into two types depending on whether our forgetting is being caused by something that happened before or after the event we want to recall. If you are having difficulty remembering the things you learned in your sociology course last semester because of the courses you are taking this semester, that is called retroactive interference. The other kind of interference occurs when you want to remember something now but are having difficulty because of things you learn in the past. This is called proactive interference. Perhaps at work you have a new routine to learn, but you are having difficulty remembering it because the old routine is such a habit that it gets in the way.