What is the difference between retroactive and proactive interference?

Retroactive interference occurs when newly learned information disrupts the recall of previously learned information. For example, learning your new phone number makes it harder to remember your old phone number. Proactive interference occurs when previously learned information disrupts the ability to remember new information. For example, your old locker combination interferes with remembering your new one. Both are major causes of forgetting. The key distinction is timing: retroactive works backward in time with new disrupting old, while proactive works forward with old disrupting new.