Assignment: Cognitive Psychology And Its Implications.
Assignment: Cognitive Psychology And Its Implications.
Respond in 500 words with some scholarly references. Use citations, cite your references. Please use attachment to answer question. Cite every sentence with content from your sources. There are a few ways to do that including just putting the citation at the end of each sentence. What did you find most interesting or “surprising” about Chapter 7?
chp_7.docx
7
Human Memory:
Retention and Retrieval
Popular fiction frequently has some protagonist who is unable to recall some critical
memory—either because of some head injury, repression of some traumatic
experience, or just because the passage of time has seemed to erase the memory.
The critical turning event in the story occurs when the protagonist is able to recover
the memory—perhaps because of hypnosis, clinical treatment, returning to an old
context, or (particularly improbable) being hit on the head again. Although our everyday
struggles with our memory are seldom so dramatic, we all have had experiences
with memories that are just at the edge of availability. For instance, try remembering
the name of someone who sat beside you in class in grade school or a teacher of a
class. Many of us can picture the person but will experience a real struggle with retrieving
that person’s name—a struggle at which we may or may not succeed. This chapter
will answer the following questions: • How does memory for information fade with the passage of time? • How do other memories interfere with the retrieval of a desired memory? • How can other memories support the retrieval of a desired memory? • How does a person’s internal and external context influence the recall
of a memory? • How can our past experiences influence our behavior without our being able
to recall these experiences? Assignment: Cognitive Psychology And Its Implications.
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•Are Memories Really Forgotten? Assignment: Cognitive Psychology And Its Implications.
Figure 7.1 repeats Figure 6.1, identifying the prefrontal and temporal structures
that have proved important in studies of memory. This chapter will focus more
on the temporal (and particularly the hippocampal) contributions to memory,
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Are Memories Really Forgotten? | 177
which play a major role in retention of memory. One of the earliest studies of
the role of the temporal cortex in memory seemed to provide evidence that
forgotten memories are still there even though we cannot retrieve them. As part
of a neurosurgical procedure, Penfield (1959) electrically stimulated portions of
patients’ brains and asked them to report what they experienced (patients were
conscious during the surgery, but the stimulation technique was painless). In
this way, Penfield determined the functions of various portions of the brain.
Stimulation of the temporal lobes led to reports of memories that patients
were unable to report in normal recall, such as events from childhood. This
seemed to provide evidence that much of what seems forgotten is still stored
in memory. Unfortunately, it is hard to know whether the patients’ memory
reports were accurate because there is no way to verify whether the reported
events actually occurred. Therefore, although suggestive, the Penfield experiments
are generally discounted by memory researchers.
A better experiment, conducted by Nelson (1971), also indicates that forgotten
memories still exist. He had participants learn a list of 20 paired associates,
each consisting of a number for which the participant had to recall a
noun (e.g. 43-dog). The subjects studied the list and were tested on it until
they could recall all the items without error. Participants returned for a retest
2 weeks later and were able to recall 75% percent of the associated nouns when
cued with the numbers. However, interest focused on the 25% that they could
no longer recall—were these items really forgotten? Participants were given
new learning trials on the 20 paired associates. The paired associates they had
missed were either kept the same or changed. For example, if a participant had
learned 43-dog but failed to recall the response dog to 43, he or she might now
be trained on either 43-dog (unchanged) or 43-house (changed). Participants
were tested after studying the new list once. If the participants had lost all
memory for the forgotten pairs, there should have been no difference between
recall of changed and unchanged pairs. However, participants correctly recalled
78% of the unchanged items formerly missed, but only 43% of the changed items.
FIGURE 7.1 The brain structures
involved in the creation and
storage of memories. Prefrontal
regions are responsible for
the creation of memories. The
hippocampus and surrounding
structures in the temporal
cortex are responsible for the
permanent storage of these
memories.
Brain Structures
Prefrontal regions
active when information
is retrieved
Hippocampal regions
(internal) active during
retrieval
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This large advantage for unchanged items indicates that participants had retained
some memory of the original paired associates, even though they had been unable
to recall them initially. Assignment: Cognitive Psychology And Its Implications.
Sometimes we can recognize things we cannot recall. So, Nelson (1978) also
conducted a similar test involving recognition rather than recall. Four weeks
after the initial learning phase, participants failed to recognize 31% of the
paired associates they had learned. As in the previous experiment, Nelson asked
participants to relearn the missed items. For half the stimuli, the responses were
changed; for the other half, they were left unchanged. After one relearning trial,
participants recognized 34% of the unchanged items but only 19% of the
changed items. Thus, even when participants failed this sensitive recognition
test, however, it appears that a record of the item was still in memory—the
evidence again being that relearning was better for the unchanged pairs than
for the changed ones.
These experiments do not prove that everything is remembered. They show
only that appropriately sensitive tests can find evidence for remnants of some
memories that appear to have been forgotten. In this chapter, we will discuss
first how memories become less available with time, then some of the factors
that determine our success in retrieving these memories.
Even when people appear to have forgotten memories, there is evidence that
they still have some of these memories stored.
•The Retention Function
The processes by which memories become less available are extremely regular,
and psychologists have studied their mathematical form. Wickelgren did some
of the most systematic research on memory retention functions, and his data
are still used today. In one recognition experiment (Wickelgren, 1975), he presented
participants with a sequence of words to study and then examined the
probability of their recognizing the words after delays ranging from 1 min to
14 days. Figure 7.2 shows performance as a function of delay. The performance
measure Wickelgren used is called d (pronounced d-prime), which is derived
from the probability of recognition. Wickelgren interpreted it as a measure of
memory strength.
Figure 7.2 shows that this measure of memory systematically deteriorates
with delay. However, the memory loss is negatively accelerated—that is, the rate
of change gets smaller and smaller as the delay increases. Figure 7.2b replots
the data as the logarithm of the performance measure versus the logarithm
of delay. Marvelously, the function becomes linear. The log of performance is
a linear function of the log of the delay T; that is,
where A is the value of the function at 1 min [log(1) = 0] and b is the slope
of the function in Figure 7.2b, which happens to be 0.30 in this case.
log d¿ = A – b log T
¿
178 | Human Memory: Retention and Retrieval
Anderson7e_Chapter_07.qxd 8/20/09 9:47 AM Page 178
This equation can be transformed to
where c _ 10A and is 3.62 in this case. That is, these performance measures are
power functions of delay. In a review of research on forgetting, Wixted and
Ebbesen (1991) concluded that retention functions are generally power functions.
This relationship is called the power law of forgetting. Recall from Chapter
6 that there is also a power law of learning: Practice curves are described by
power functions. Both functions are negatively accelerated, but with an important
difference. Whereas practice functions show diminishing improvement
with practice, retention functions show diminishing loss with delay.
A very dramatic example of the negative acceleration in retention function
was produced by Bahrick (1984), who looked at participants’ retention of English-
Spanish vocabulary items anywhere from immediately to 50 years after they
had completed courses in high school and college. Figure 7.3 plots the number
of items correctly recalled out of a total of 15 items as a function of the logarithm
of the time since course completion. Separate functions are plotted for
students who had one, three, or five courses. The data show a slow decay of
knowledge combined with a substantial practice effect. In Bahrick’s data, the
retention functions are nearly flat between 3 and 25 years (as would be predicted
by a power function), with some further drop-off from 25 to 49 years (which is
more rapid than would be predicted by a power function). Bahrick (personal
communication, circa 1993) suspects that this final drop-off is probably related
to physiological deterioration in old age.
There is some evidence that the explanation for these decay functions may
be found in the associated neural processes. Recall from Chapter 6 that longterm
potentiation (LTP) is an increase in neural responsiveness that occurs as a
reaction to prior electrical stimulation.We saw that LTP mirrors the power law
d¿ = cT-b
The Retention Function | 179
(a) (b)
0
1.0
2.0
5
Delay, T (days)
3.62T −0.321
Measure of retention (d ʹ)
10 15 20 1
.1
2
.2
.5
1.0
2.0
3.0
4 7 15 30 50 1 2 4 71014
Minutes
log d ʹ
Days
log T