what is the difference between proactive and retroactive interference?

Retroactive interference and proactive interference refers to different types of contamination memory. It affects occurs in our LTM when 2 pieces of information conflict not allowing us access to memories despite their presence/availability. Retroactive (RI) interference occurs when a newer memory disrupts and older memory, most people find this difficult to remember as retro is associated with something old (hence people mix them up). Proactive interference (PI) occurs when older memories disrupt more recent memories, an example of this might be your trying to remember you order of your class register and mixing it up with last years register. Interference is worst when the memories are most similar! which is why it's difficult to correctly learn which 'active' interferes with which presence. But I find the best way to remember it is that retroactive - retro= old/ outdated, thus older memories replaced by the newer memories.Proactive memories, pro (similar to pre) = pre = previous ... memories are disrupting the newer memory you want to learn