THEORIES OF FORGETTING : Trace decay
This is a biological explanation for forgetting.
It has been proposed that memory traces decay i.e. fade away over time.
Hebb (1949) argued that new memories
cause changes in the brain creating a
neurological memory trace and that this,
if not used occasionally, will eventually
fade away. When information is received
into STM the new information leaves a
delicate physiological trace in the brain
due to the activation of neurons. This
trace is called an engram. According to
this explanation the information remains
in STM for as long as this engram
remains intact/unchanged.
However, the engram decays (degrades) naturally over
time (duration) unless it is maintained.
Maintenance can occur through either:
Rehearsal of the information or frequent recall of
information.
If the engram is maintained in either of these ways it
becomes more permanent with additional learning and
repetition.
If neither of these occurs the memory (engram) will be forgotten.
So if new information is sufficiently rehearsed the trace is reinforced, becomes fixed
permanently in LTM and does not fade.
According to Hebb's theory then, trace decay only occurs from STM.
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Research Evidence : Drag and Drop each section of the research study into its
correct place.
Decay in Short Term Memory
Reitman (1974)
Study
Aim
To investigate whether decay could cause forgetting
Method
Results
Conclusions
Activity : Identify 2 limitations of this research study.
Limitations of the
research
Male students were shown a list of five words for 2
seconds. They then listened out for a faint tone through a
pair of headphones (given at 15 seconds).
Then they tried to recall the words.
As the tone detection task required effort thus preventing
memorizing the words but no new information was
received; then the loss must have been due to decay.
Word recall fell by 24% over the 15 second
interval
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Strengths :

One strength of trace decay as an explanation of forgetting in STM is that it has
supporting research provided by Reitman ( above).

A further strength of trace decay is that the research on which it is based is
repeatable. Research into the nature of forgetting in STM is carried out in a
controlled lab environment where all variables can be measured and manipulated.
As a result this type of research is scientific. This suggests that research into
the nature of forgetting in STM is reliable.
Weaknesses :

One weakness of trace decay is that it has opposing evidence provided by Jenkins
and Dallenbach (1924).
Jenkins & Dallenback (1924)
Method : In this study 2 groups of participants had to learn 10 nonsense syllables.
Group 1 went to sleep immediately after learning, group 2 carried on with their normal
daytime activities. All participants were then tested after 1, 2, 4 or 8 hours after the
initial learning.
If decay is the primacy source of forgetting, then the rates of forgetting should be
similar in the awake and the sleep conditions.
Results :
Group 1 (who slept) had the lowest level of forgetting, whereas group 2 (who stayed
awake) had far greater levels of forgetting.
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This suggests that forgetting in STM may not be due to trace decay as it cannot
account for the lower levels of forgetting in group 1, and hence other factors must play
a part like interference.

A further weakness of trace decay is that the research on which it is based lacks
ecological validity. Research supporting trace decay explanation has been carried
out in an artificial, laboratory setting. When meaningful material is used, trace
decay is harder to demonstrate. This suggests that the ideas of trace decay
explanation cannot be applied to real life settings.
Although this section is concerned with forgetting from STM, it is important to note
that some researchers argue that memory traces in LTM are susceptible to decay if
these memories are not used. The problem with this aspect of trace-decay theory is
that it does not explain why some trivia and unimportant material, such as song titles and
commercial jingles, seem to persist in memory. Neither does it account for the fact that
we do not lose skills such as riding a bike or playing the piano, even though we may not
have done so for many years.
Bahrick (1984) found that people still remembered a substantial amount of Spanish 50
years after taking the subject at school, although most had hardly used Spanish at all in
the intervening years.
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