254 CHAPTER 6
times when people can recall memories they had assumed were long for-
gotten. There must be other factors involved in the forgetting of long-term
memories.
INTERFERENCE THEORY A possible explanation of LTM forgetting is
that although most long-term memories may be stored more or less per-
manently in the brain, those memories may not always be accessible to
attempted retrieval because other information interferes (Anderson &
Neely, 1995). (And even memories that are accessible are subject to con-
structive processing, which can lead to inaccurate recall.) An analogy
might be this: The can of paint that Phillip wants may very well be on some
shelf in his storeroom, but there’s so much other junk in its way that he
can’t see it and can’t get to it. In the case of LTM, interference can come
from two different “directions.”
PROACTIVE INTERFERENCE Have you ever switched from driving a car with
the gearshift on the steering wheel to one with the gearshift on the floor of the
car? If the answer is yes, you probably found that you had some trouble when
you first got into the new car. You may have grabbed at the wheel instead of
reaching to the gearshift on the floor. The reason you reached for the gear-
shift in the “old” place is called proactive interference: the tendency for older
or previously learned material to interfere with the learning (and subsequent
retrieval) of new material. (See Figure 6.9.)
Another example of proactive interference often occurs when someone
gets a new cell phone number. People in this situation often find themselves remember-
ing their old cell phone number or some of its digits instead of the new cell phone num-
ber when they are trying to give the new number to friends.
RETROACTIVE INTERFERENCE When newer information interferes with the retrieval of
older information, this is called retroactive interference. (See Figure 6.9.) What hap-
pens when you change back from the car with the gearshift on the floor to the older car
with the gearshift on the wheel? You’ll probably reach down to the floor at least once or
twice because the newer skill retroactively interferes with remembering the old way of
doing it.
How might interference work in each of the following cases?- Moving from the United States to England, where people drive on the left instead
of the right side of the road. - Trying to use the controls on your old Blu-ray® player after having used the new
one for a year. - Moving from one type of cell phone system to another, such as going from an
iPhone® to an Android® system.
The different ways that forgetting occurs are summarized in Table 6.1.
proactive interference
memory problem that occurs when
older information prevents or inter-
feres with the learning or retrieval of
newer information.
retroactive interference
memory problem that occurs when
newer information prevents or
interferes with the retrieval of older
information.
Figure 6.9 Proactive and Retroactive Interference
If a student were to study for a French exam and then a
Spanish exam, interference could occur in two directions.
When taking the Spanish exam, the French information stud-
ied first may proactively interfere with the learning of the new
Spanish information. But when taking the French exam, the
more recently studied Spanish information may retroactively
interfere with the retrieval of the French information.
French, learned beforehand, interferes proactively
Study French Study Spanish Spanish TestProactive InterferenceSpanish, learned afterwards, interferes retroactively
Study French Study Spanish French TestRetroactive InterferenceInteractiveTable 6.1 Reasons for Forgetting
Reason Description
Encoding Failure The information is not attended to and fails to be encoded.
Decay or Disuse Information that is not accessed decays from the storage system
over time.
Proactive Interference Older information already in memory interferes with the learning of
newer information.
Retroactive Interference Newer information interferes with the retrieval of older
information.The answer to Figure 6.8 is the middle right
image.