Answer to Question 1
Our memories tend to be good when we use distributed practice, learning in which various sessions are spaced over time. Our memories for information are not as good when the information is acquired through massed practice, learning in which sessions are crammed together in a very short space of time. The greater the distribution of learning trials over time, the more the participants remembered over long periods. To maximize the effect on long-term recall, the spacing should ideally be distributed over months, rather than days or weeks. This effect is termed the spacing effect. Thus the primary advantage is improved recall while the primary disadvantage is the amount of time over which the practice must occur.
Answer to Question 2
Interference theory refers to forgetting that occurs because recall of certain information interferes with recall of other information. Retroactive interference (or retroactive inhibition) occurs when newly acquired knowledge impedes the recall of older material.
Proactive interference (or proactive inhibition) occurs when material that was learned in the past impedes the learning of new material.
Decay theory asserts that information is forgotten because of the gradual disappearance, rather than displacement, of the memory trace. Thus, decay theory views the original piece of information as gradually disappearing unless something is done to keep it intact. This view contrasts with interference theory, in which one or more pieces of information block recall of another.
Evidence exists for both interference and decay, at least in short-term memory. There is some evidence for decay, but the evidence for interference is much stronger. For now, we can assume that interference accounts for most of the forgetting in short-term memory. However, the extent to which the interference is retroactive, pro- active, or both is unclear. In addition, interference also affects material in long-term memory, leading to memory distortion.