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Freud proposed that unwanted memories can be forgotten by pushing them into the unconscious, a process called repression. The existence of repression has remained controversial for more than a century, in part because of its strong coupling with trauma, and the ethical and practical difficulties of studying such processes in controlled experiments. However, behavioural and neurobiological research on memory and attention shows that people have executive control processes directed at minimizing perceptual distraction, overcoming interference during short and long-term memory tasks and stopping strong habitual responses to stimuli. Here we show that these mechanisms can be recruited to prevent unwanted declarative memories from entering awareness, and that this cognitive act has enduring consequences for the rejected memories. When people encounter cues that remind them of an unwanted memory and they consistently try to prevent awareness of it, the later recall of the rejected memory becomes more difficult. The forgetting increases with the number of times the memory is avoided, resists incentives for accurate recall and is caused by processes that suppress the memory itself. These results show that executive control processes not uniquely tied to trauma may provide a viable model for repression.
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We thank D. Osorio for help with colour registration; E. Ting, P. Y. Cheng, I. C. Bruce,
R. T. Corlett, L. Ramsden, N. Yamashita and A. Walker for comments, P. Kagoro,
B. Balyeganira and M. Musana for ®eld assistance in Uganda; J. Magnay, R. W. Wrangham
and C. A. Chapman for logistic support in Uganda; and the Ugandan National Council for
Science and Technology, Ugandan Wildlife Authority and Makerere University Biological
Field Station for permission to work at Kibale. Supported by Research Grants Council of
Hong Kong, National Geographic Society, Sigma Xi, Explorer's Club and Croucher
Foundation of Hong Kong.
Correspondence and requests for materials should be addressed to N.J.D.
Suppressing unwanted memories by
executive control
Michael C. Anderson & Collin Green
Department of Psychology, University of Oregon, Eugene, Oregon 97403-1227,
Freud proposed that unwanted memories can be forgotten by
pushing them into the unconscious, a process called repression
The existence of repression has remained controversial for more
than a century, in part because of its strong coupling with trauma,
and the ethical and practical dif®culties of studying such pro-
cesses in controlled experiments. However, behavioural and
neurobiological research on memory and attention shows that
people have executive control processes directed at minimizing
perceptual distraction
, overcoming interference during short
and long-term memory tasks
and stopping strong habitual
responses to stimuli
. Here we show that these mechanisms
can be recruited to prevent unwanted declarative memories from
entering awareness, and that this cognitive act has enduring
consequences for the rejected memories. When people encounter
cues that remind them of an unwanted memory and they con-
sistently try to prevent awareness of it, the later recall of the
rejected memory becomes more dif®cult. The forgetting increases
with the number of times the memory is avoided, resists incen-
tives for accurate recall and is caused by processes that suppress
the memory itself. These results show that executive control
processes not uniquely tied to trauma may provide a viable
model for repression.
Executive control processes studied in behavioural
research on cognition may provide a
mechanism for the voluntary form of repression (suppression)
proposed by Freud
. To test this hypothesis, we adapted the go/
no-go paradigm used to study executive control over motor actions
in primates
and humans
for use in a memory retrieval task.
First, we trained subjects on 40 unrelated word pairs (for example,
ordeal±roach) so that they could recall the right-hand member of
each pair when provided with the left-hand member. Next, subjects
performed a critical task requiring them to exert executive control
over the retrieval process. On each trial of this think/no-think task, a
cue from one of the pairs appeared on the computer screen.
Depending on which cue appeared, subjects were told either to
recall and say (think about) the associated response word (respond
pairs), or not to think about the response (suppression pairs). For
the latter pairs, we emphasized that subjects should not allow the
associated memory to enter consciousness at all. If subjects acci-
dentally responded to a suppression pair, they heard a beep signal-
ling an error. To increase the need to recruit inhibitory control
mechanisms, we required subjects to ®xate on the cue word for the
entire time (4 s) that it appeared on the screen, discouraging
perceptual avoidance and generating a constant threat that the
associated memory might intrude into consciousness. Thus, sup-
pression trials required the stopping of both a prepotent motor
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Number of repetitions
Per cent recalled
Same probe Independent probe
Figure 1 Final recall for respond and suppression items as a function of the number of
repetitions for the same-probe (SP) and independent-probe (IP) tests. a, b, Experiment 1;
c, d, experiment 2; e, f, experiment 3; g, averaged across experiments. Note the negative
slope for recall of the suppressed item, indicating increasing inhibition. Inhibition (0 vs 16
suppressions) was signi®cant (P , 0.01) in all experiments, and did not interact with type
of test cue (F , 1 in all cases; analysis of variance). Inhibition was signi®cant (P , 0.05) in
every SP and IP test for every experiment (a±f).
© 2001 Macmillan Magazines Ltd
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15 MARCH 2001
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response and the entrance of an unwanted memory into awareness.
Before this phase, we told subjects which cues would require
suppression so that they would recognize these words on sight.
Subjects performed suppression and respond trials on different
pairs that were intermixed. On each trial, no visual marking
indicated which cue words were suppression items, forcing subjects
to identify each cue to know whether to recall or suppress the
associated memory.
The objective of the think/no-think task was to determine
whether attempting to prevent awareness of an unwanted
memory would hinder its later retrieval. To evaluate whether this
occurred, the next phase required subjects to recall the response for
each of the cue words. We emphasized that the previous goal of
avoiding the associated items was no longer relevant and that a
response should be recalled for every cue. If trying to prevent a
memory from entering awareness recruits inhibitory control pro-
cesses that impair that memory's retrievability, recall for suppres-
sion items should be worse than for baseline pairs on this test. In all
experiments reported here, baseline items were studied pairs that
did not appear as either respond or suppression items during the
think/no-think phase.
In experiment 1, we varied the number of suppression or respond
trials given for each pair. Subjects received 0, 1, 8 or 16 trials for each
suppression and each respond item. If excluding unwanted mem-
ories from awareness recruits inhibitory control, recall should be
worse after 16 suppression attempts than after 0 attempts (baseline).
As shown in Fig. 1a, ®nal recall of suppressed items was worse than
of baseline items, and impairment increased linearly with suppres-
sion practice. In contrast, recall improved across repetitions for
respond items, demonstrating the established bene®ts of retrieving
memories on their later recall. These diverging patterns show that
controlling awareness not only terminated the powerful facilitative
effects of retrieval, but also impaired the recall of suppressed items
to below their baseline level (0 suppression attempts). The increas-
ing inhibition with repetition further indicates that unwanted
memories might be especially vulnerable in settings requiring
protracted avoidance, unlike the modest time (1 min over 16
suppressions) afforded by our task.
Impaired memory for suppression items indicates that there may
be an executive control process that suppresses (reduces activation
of) the unwanted memory itself (for example, roach in Fig. 2).
However, mechanisms other than inhibition may be at work
instance, one strategy for avoiding an unwanted memory would be
to generate diversionary thoughts to environmental stimuli that
remind us of it. New associations between these stimuli and the
diversionary thoughts may interfere during later attempts to recall
the memory. Alternatively, terminating retrieval may degrade the
association between the cue and the response. Neither of these
alternatives requires us to assume that the unwanted memory itself
is inhibited and thus they do not require the postulation of an
executive inhibition process. To isolate the contribution of inhibi-
tion, we used the independent probe method
. If inhibition impairs
the unwanted memory itself, recall should be worse regardless of
whether that item is tested with the cue used to train suppression or
with a novel cue (Fig. 2). However, associative interference and
unlearning predict that forgetting should be limited to the originally
trained cue. To distinguish between these models, we retested
subjects from experiment 1 with cues not previously encountered
in the experiment (`independent probes'). For each item, we cued
subjects with a semantic category and the initial letter of the
response word (for example, for ordeal±roach, subjects received
`insect r___') and asked them to recall the studied word that ®t the
cues. On this new independent probe (IP) test, recall of suppressed
items was again worse than baseline (Fig. 1b), and the impairment
was higher when recall had been avoided more. The amount of
forgetting did not differ reliably from when the originally trained
cue was used in the test (for example, ordeal in the same probe (SP)
test condition, Fig. 1a). This ®nding rules out associative inter-
ference and unlearning and shows that impairment is localized to
the unwanted memory itself. This strongly supports the existence of
an inhibitory control mechanism
It was necessary to show that subjects did not recall and then
withhold suppression items on the ®nal test. They might have done
so out of confusion, given our emphasis on withholding responses
during the think/no-think phase. To address this, we expanded our
test instructions to emphasize that subjects should recall an item to
every cue regardless of earlier instructions, even if they were
guessing. To further encourage responding, we offered a monetary
reward for correct answers. These incentives had little impact on the
inhibition effect (Fig. 1c, d). Impairment was signi®cant overall,
increased with repetition, and did not vary with the type of test cue,
again supporting the inhibitory control view. Although the instruc-
tions to guess enhanced recall of suppression and baseline items
when the studied cue was given (P , 0.01), the linear trend for
inhibition did not differ reliably across experiments (F , 1).
Subjects might have guessed the hypothesis of the experiment and
tried to conform to the expectation of impaired memory by with-
holding items. To address this, we altered the ®nal test instructions
Insect r__
Diversionary thoughts
Trained cue Independent cue
Figure 2 Three mechanisms that can explain impaired recall in the same-probe condition,
illustrated with a stimulus pair. Associative interference posits that suppression training
leads subjects to generate diversionary thoughts (1) to the trained cue that interfere during
later attempts to recall the target. Unlearning assumes that suppression training weakens
the cue±target connection (2). The suppression hypothesis states that suppression
training inhibits the target (3). Note that testing the target with an independent cue
circumvents interference (1) and unlearning (2). Any impairment found with this test may
be attributed to effects localized to the target.
© 2001 Macmillan Magazines Ltd
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VOL 410
15 MARCH 2001
to make subjects believe that we expected improved memory for
suppression items. We told subjects that research suggests that when
people try not to think about something, they ironically think about
it more, as when people try not to think about falling asleep at night
and then experience insomnia
. We noted that this research pre-
dicts that memory for suppression items should improve because
the avoided memories should intrude during suppression trials.
Post-experimental questionnaires indicated that subjects believed
that this was our rationale (average rating of 4.2 on a 5-point belief
scale) and most endorsed the theory on the basis of experience.
These new test instructions had little effect on the inhibition pattern
(Fig. 1e, f).
Success in our think/no-think task is de®ned by participants'
subjective awareness of the unwanted memory during suppression
trials, a state which cannot be measured. Efforts to control this state
nevertheless left their mark on memory. However, the apparent
memory de®cit may re¯ect suppression of the overt motor response
associated with the unwanted memory. To test this, we removed the
instruction to suppress awareness of the memory during the think/
no-think phase. We instead asked subjects to recall the memory,
but not say it aloud, rendering this an episodic go/no-go task.
Recall did not decline with the number of verbal suppressions, and
this pattern did not vary with the cue used to test items (Fig. 3a,
b). In contrast, when experiments 1±3 are combined, the linear
trend for inhibition was reliable for the SP and IP test conditions
(P , 0.001, Fig. 1g) and these effects did not vary reliably across
experiments. Importantly, the linear inhibition effect was statisti-
cally larger in the think/no-think task (experiments 1±3) than in
the go/no-go task (experiment 4). These ®ndings isolate impaired
recall of unwanted memories to cognitive operations directed at
keeping them out of awareness.
Our results imply that a process exists that impairs the retention
of memories when they are deliberately kept out of consciousness.
When people encounter a stimulus that is known to cue an
unwanted memory, this process can be recruited to prevent aware-
ness of the memory. The regulation of consciousness is accom-
plished by an inhibitory control mechanism that suppresses the
unwanted memory itself (as shown by our independent probe data),
and not merely by the momentary ®lling of working memory with
diversionary thoughts. Delayed recall of the unwanted memory is
worse than a baseline condition in which no reminders of the
memory were presented in the interim. This paradoxical pattern
arises because repeated exposure to reminders makes it necessary
for people to adapt their patterns of thought internally with
executive control processes. Thus, frequent encounters with remin-
ders should make an unwanted memory less accessible, a ®nding
noted in some clinical studies of psychogenic amnesia
Our results clarify the nature and scope of inhibitory processes
previously shown to impair episodic recall, and link those processes
to behavioural and neurobiological research on executive control.
Work on retrieval-induced forgetting
has shown that memories
that interfere with the retrieval of other targets are inhibited, but it
has not previously been established whether inhibition is under
strategic control. Research into directed forgetting
suggests a
controllable inhibition process, but one limited in scope to an
immediately preceding temporal interval. The present ®ndings
show a controllable inhibition process that can be ¯exibly targeted
to a speci®c prepotent memory after intervening memories have
been acquired. These ®ndings do not support the popular idea that
attempting to suppress an unwanted thought makes it hyperac-
cessible, at least as this idea applies to suppressing episodic
The need to terminate retrieval in the think/no-think paradigm
can be viewed as one instance of the need to override prepotent or
habitual responses when they are inappropriate, a function pre-
sumed to require executive control
. Related tasks such as
the go/no-go procedure are widely used to study this executive
function and have been shown to recruit dorsolateral prefrontal
cortex (DLPFC) and anterior cingulate cortex (ACC) (with ventral
. Other studies show a speci®c role of DLPFC in over-
coming interference from competing representations in working
, in selecting one item in working memory as the basis for
and in on-line manipulation of information
. The
sustained regulation of awareness required by our procedure is likely
to use such processes. This suggests that the think/no-think task
recruited DLPFC and ACC, perhaps with medial temporal regions,
to control awareness of the memory
. If this is true, the present
memory de®cits provide a behavioural marker of the action of this
network on rejected memories and suggest that this network exerts
control through inhibition
Whatever their neural basis, our results establish a direct link
between internal operations that control phenomenal awareness
of a memory and its later accessibility. These ®ndings thus
support a suppression mechanism that pushes unwanted mem-
ories out of awareness, as posited by Freud. Research on retrieval-
induced forgetting shows that suppression can have a lasting
impact on a memory's accessibility
. Suppression in the current
paradigm may be similarly enduring. Furthermore, if retrieving
diversionary thoughts becomes habitual, inhibition may be sus-
tained without any intention of avoiding the unwanted memory
Together, these factors provide a viable model of repression, and
its potential evolution from an intentional to an unintentional
process. If so, repression may not be tied uniquely to psycho-
logical defence, but may rather re¯ect the action of a general
executive control process, directed at declarative memories of past
Thirty-two neurologically normal college students participated in each experiment, except
experiment 4, in which there were sixteen. Each participant was trained on 40 critical and
10 ®ller word pairs. The stimulus and response members of each pair had a weak pre-
experimental relationship, and were unrelated to words in other pairs. The response
members were chosen so that each was a member of its own category (for example,
insects), to permit later testing of that item with an extralist category cue. The word pairs
were exposed individually for 5 s in the centre of a computer screen with the response
printed to the right of the stimulus. Test±feedback cycles followed in which subjects were
presented with the stimulus member and asked to say the response aloud as quickly as
possible. The correct answer was given visually if the response was omitted. Test±feedback
cycles on all the pairs continued until a minimum of 50% of the pairs were correctly
After initial study, subjects were given the think/no-think phase instructions, and were
then presented with the 15 stimulus members from the to-be-suppressed pairs without
their responses. Subjects familiarized themselves with the stimuli so that they could
identify them during suppression trials and prevent the associated memory item from
coming to mind. After a brief practice session on the think/no-think task using ®ller items,
subjects were given 377 trials in which respond and suppression stimuli were randomly
Number of repetitions
Per cent recalled
01 816
Number of repetitions
Per cent recalled
Same probe
Independent probe
Figure 3 Final recall of withhold and respond items as a function of the number of
repetitions. a, Performance in the same test probe (SP) condition. b, Performance in the
independent probe condition (IP). In both conditions, withhold item performance does not
decrease with repetition. None of the inhibition effects were signi®cant (F , 1 in all
cases). There was reliably more inhibition in experiments 1±3 than in experiment 4
(P , 0.05), and a reliably greater linear trend for inhibition (P , 0.05). Neither of these
tendencies interacted with type of test cue (F , 1).
© 2001 Macmillan Magazines Ltd
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VOL 410
15 MARCH 2001
| 369
intermixed. On each trial, a ®xation cross appeared for 200 ms, followed by a stimulus
member in the centre of the screen. For respond trials, the stimulus was presented for
up to 4 s, or until the subject responded, and subjects had to report the response as
quickly as possible. For suppression trials, the stimulus remained on the screen for 4 s.
If a subject responded, a loud error beep sounded. Trials were separated by a 400-ms
intertrial interval. Suppression and respond trials were conducted on different word
pairs, with ®ve pairs participating in each of the 0 (baseline), 1, 8 and 16-repetition
conditions for both the respond and suppression conditions. Respond trials on ®ller
pairs were also included so that 67% of the trials in the think/no-think phase required a
response, encouraging a strong mental set to respond that had to be overridden, as in
go/no-go tasks.
After the think/no-think phase, we tested the subjects' memory for all of the word pairs
in two ways. In both tests, a cue for each word pair was presented in the centre of the screen
for up to 4 s, or until subjects spoke the response. Pairs for the different respond and
suppress conditions were intermixed pseudo-randomly, with the constraint that the
average test position for each condition was equated. In the same-probe test, subjects'
recall for each pair was cued with the stimulus member that was paired with the response
throughout the experiment. In the independent probe test, subjects were cued with the
category name for each exemplar along with its ®rst letter. In each case, subjects were asked
to recall the studied item that ®t the cues and not to withhold any items. Half of the
subjects in each experiment got the same-probe test ®rst, and half were given the
independent probe test ®rst.
Subjects in experiment 2 were given 25 cents for each correct answer, up to a maximum
of $4. Subjects in experiment 3 were given a questionnaire after the experiment in which
they were asked about their impressions of our (false) hypothesis that memory would
improve with attempts to suppress an item.
Received 10 October; accepted 21 December 2000.
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Masking unveils pre-amodal
completion representation
in visual search
Robert Rauschenberger & Steven Yantis
Department of Psychology, The Johns Hopkins University, Baltimore,
Maryland 21218, USA
When one object is partly occluded by another, its occluded parts
are perceptually `®lled in', that is, the occluded object appears to
continue behind its occluder. This process is known as amodal
. The completion of a partially occluded object takes
about 200 ms (ref. 2), and pre-completion information (that is,
information from before amodal completion has occurred) exists
in the visual system for that duration
. It has been suggested,
however, that observers cannot make use of this information, even
when it is bene®cial to do so: visual search for a target that appears
to be partly occluded, for example, is slower than for a target that
does not undergo occlusion, despite both targets being physically
. Here we show that visual search does have access to
pre-completion representations, but only for a limited time that
depends on the size of the occluded region.
Early investigations of visual search focused on discovering the
elementary features available in early vision
, whereas more
recent work has demonstrated that the input to visual search is
much more complex than previously assumed
. Although it
seems that the entry level for vision (that is, entire objects or
individual features) can be quite high in many cases, questions
remain about the nature of the information available at earlier stages
of processing. In the case of amodal completion, for example, it
seems that visual search relies on a post-completion representation
even when this impairs search
. This ®nding can be interpreted in
at least three ways. First, it could be that there is no pre-amodal
completion stage in processing. This is unlikely because other
studies have shown that pre-completion information is available
for certain perceptual judgements
. Second, it is possible that pre-
completion information exists only implicitly, as an `ingredient' in
the computation of a completed representation, and is not explicitly
available for all perceptual judgements. Examples of this include
monocular information during binocular rivalry
, and very high
spatial frequency information
, both of which are present in
Table 1 Percentage of mean target-absent error rates
Experiment Number of items in display
Medium notch (100-ms SOA) 11.4 17.7 20.3 12.3
Medium notch (250-ms SOA) 3.5 4.6 5.5 3.0
Small notch 18.7 19.8 22.5 15.6
Large notch 2.0 4.0 3.0 1.9
© 2001 Macmillan Magazines Ltd
... To examine this question, we used multivariate decoding of EEG recordings to track memory intrusion during the Think/No-Think (TNT) task, 35 based on bottom-up capture during an attention task (see Figure 1). The TNT paradigm is designed to induce intrusive memories triggered by a cue whose long-term accessibility is reduced after several suppression attempts. ...
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Intrusive memories hijack consciousness and their control may lead to forgetting. However, the contribution of reflexive attention to qualifying a memory signal as interfering is unknown. We used machine learning to decode the brain's electrical activity and pinpoint the otherwise hidden emergence of intrusive memories reported during a memory suppression task. Importantly, the algorithm was trained on an independent attentional model of visual activity, mimicking either the abrupt and interfering appearance of visual scenes into conscious awareness or their deliberate exploration. We could generalize the decoding of intrusion into conscious awareness and the decoding accuracy increased when the algorithm was trained using a model of reflexive attention. Conscious detection of intrusive activity decoded from the brain signal was central to the future silencing of suppressed memories and later forgetting. Unwanted memories require the reflexive orienting of attention and access to consciousness to be suppressed effectively by inhibitory control.
It is important for mental health to be able to control unwanted intrusive memories. Previous studies suggest that middle frontal gyrus (MFG) down regulates pathways underlie the suppression of retrieval of general memories. However, the neural basis of motivated forgetting of autobiographical memories is unclear. Therefore, this study used two samples to explore the neural mechanisms of motivated forgetting of self-referential memories. Every participant provided 40 life events (20 negative and 20 neutral) from their past personal experience, and then completed the Think/No-Think task while undergoing functional magnetic resonance imaging (fMRI). The first sample showed a significant reduction in recall in the No-Think condition relative to the Think condition. Attempting to exclude negative autobiographical memories from awareness was associated with increased activity in the right MFG, superior frontal gyrus (SFG), and inferior frontal gyrus (IFG), while reduced activity was observed in the bilateral Brodmann areas BA18 and BA19, bilateral medial prefrontal cortex (mPFC), bilateral precuneus, bilateral post cingulate cortex (PCC), the left parahippocampus, and the left hippocampus. Functional connectivity analyses showed that the right MFG projected into the bilateral mPFC, bilateral precuneus, and bilateral middle occipital gyrus (MOG) for negative autobiographical memories. The second sample replicated the results of the first sample at both the behavioral and brain levels. These results suggest that retrieval suppression of autobiographical memories involve the pathway between the MFG and the mPFC and precuneus to exclude self-referential memories. These results reveal how people engage in motivated forgetting of negative events in their daily lives.
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Whenever we face a new problem, we recall the similar ones we encountered in the past, so we try to solve it with all the information available to us. Memory therefore serves to reveal our life story. This requires us to take a closer look at how memory plays such a role, and at the scientific methods used to demonstrate it. Scientific psychological studies were developed from 1873 in order to study memory and they are presented and discussed here. Other approaches are possible, however. They were developed most notably by neurosciences and psychoanalysis, two sharply contrasting disciplines born at nearly the same time. We conclude with the replication crisis that has confronted psychology more recently and with the means to resolve it.
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Typical consciousness can be defined as an individual-specific stream of experiences. Modern consciousness research on dynamic functional connectivity uses clustering techniques to create common bases on which to compare different individuals. We propose an alternative approach by combining modern theories of consciousness and insights arising from phenomenology and dynamical systems theory. This approach enables a representation of an individual’s connectivity dynamics in an intrinsically-defined, individual-specific landscape. Given the wealth of evidence relating functional connectivity to experiential states, we assume this landscape is a proxy measure of an individual’s stream of consciousness. By investigating the properties of this landscape in individuals in different states of consciousness, we show that consciousness is associated with short term transitions that are less predictable, quicker, but, on average, more constant. We also show that temporally-specific connectivity states are less easily describable by network patterns that are distant in time, suggesting a richer space of possible states. We show that the cortex, cerebellum and subcortex all display consciousness-relevant dynamics and discuss the implication of our results in forming a point of contact between dynamical systems interpretations and phenomenology.
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Accumulating research has shown that acute exercise can enhance memory function. Although counterintuitive, acute exercise may also facilitate aspects of forgetting. Specifically, retrieving a subset of items from memory can facilitate the retention of retrieved items (retrieval practice) and inhibit the subsequent retrieval of non-retrieved items from the same category (retrieval-induced forgetting; RIF). Given that acute exercise has been shown to enhance cognition-related inhibition, acute exercise may facilitate RIF, which was evaluated in three experiments. In Experiment 1, a sample of 180 young adults completed either a control (N = 60), moderate-intensity acute exercise (N = 57), or vigorous-intensity acute exercise session (N = 63). Both acute exercise sessions lasted 20 min and occurred prior to the study list. Participants then completed a standard RIF protocol, with the final test occurring via a recognition task. Acute exercise, regardless of intensity, had no effect on RIF. Experiment 2 (N = 225) was similar to Experiment 1 but used a cued recall final test, and also showed no effects of acute exercise on RIF. In Experiment 3 (N = 158), two cued recall tests were implemented, with acute exercise occurring between the two tests. Acute exercise, but not a control scenario, preserved the RIF effect across the cued recall assessments. These findings suggest that acute exercise prior to study may not influence RIF, but when positioned between two recall assessments, acute exercise may preserve the RIF effect over time.
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Processes that might facilitate the forgetting of unwanted experiences typically require the actual or imagined re-exposure to reminders of the event, which is aversive and carries risks to people. But it is unclear whether awareness of aversive content is necessary for effective voluntary forgetting. Disrupting hippocampal function through retrieval suppression induces an amnesic shadow that impairs the encoding and stabilization of unrelated memories that are activated near in time to people’s effort to suppress retrieval. Building on this mechanism, here we successfully disrupt retention of unpleasant memories by subliminally reactivating them within this amnesic shadow. Critically, whereas unconscious forgetting occurs on these affective memories, the amnesic shadow itself is induced by conscious suppression of unrelated and benign neutral memories, avoiding conscious re-exposure of unwelcome content. Combining the amnesic shadow with subliminal reactivation may offer a new approach to voluntary forgetting that bypasses the unpleasantness in conscious exposure to unwanted memories.
Multiple types of memory guide attention: Both long-term memory (LTM) and working memory (WM) effectively guide visual search. Furthermore, both types of memories can capture attention automatically, even when detrimental to performance. It is less clear, however, how LTM and WM cooperate or compete to guide attention in the same task. In a series of behavioral experiments, we show that LTM and WM reliably cooperate to guide attention: Visual search is faster when both memories cue attention to the same spatial location (relative to when only one memory can guide attention). LTM and WM competed to guide attention in more limited circumstances: Competition only occurred when these memories were in different dimensions - particularly when participants searched for a shape and held an accessory color in mind. Finally, we found no evidence for asymmetry in either cooperation or competition: There was no evidence that WM helped (or hindered) LTM-guided search more than the other way around. This lack of asymmetry was found despite differences in LTM-guided and WM-guided search overall, and differences in how two LTMs and two WMs compete or cooperate with each other to guide attention. This work suggests that, even if only one memory is currently task-relevant, WM and LTM can cooperate to guide attention; they can also compete when distracting features are salient enough. This work elucidates interactions between WM and LTM during attentional guidance, adding to the literature on costs and benefits to attention from multiple active memories.
To what extent do creativity and imagination decline in childhood? What factors might influence a decline? Theories of cognitive development show only uni-directional progress (although theorists may disagree whether such progress occurs steadily in small continuous improvements or comes in stages separated by plateaus during which developmental gains are consolidated). Declines in levels of skill are quite uncommon, yet many have observed just such an unusual pattern with regard to the development of creativity and of the imagination. Is there something about the development of one kind of thinking that undermines imaginative and creative thinking? Is it perhaps the process of schooling itself, with its focus on the acquisition of knowledge and the production of correct (rather than imaginative) answers, which promotes this decline? This book explores these questions from a variety of perspectives. Essays from psychologists and educators from diverse backgrounds discuss the relationships among creativity, reason, and knowledge.
This innovative textbook is the first to integrate learning and memory, behaviour, and cognition. It focuses on fascinating human research in both memory and learning (while also bringing in important animal studies) and brings the reader up to date with the latest developments in the subject. Students are encouraged to think critically: key theories and issues are looked at in detail; descriptions of experiments include why they were done and how examining the method can help evaluate competing viewpoints. By looking at underlying cognitive processes, students come away with a sense of learning and memory being interrelated actions taken by the same human being, rather than two separate activities. Lively and engaging writing is supported by lots of examples of practical applications that show the relevance of lab-based research to everyday life. Examples include treatments for phobias and autism, ways to improve eyewitness testimony, and methods of enhancing study techniques.
There is now ample evidence from the preclinical and clinical fields that early life trauma has both dramatic and long-lasting effects on neurobiological systems and functions that are involved in different forms of psychopathology as well as on health in general. To date, a comprehensive review of the recent research on the effects of early and later life trauma is lacking. This book fills an obvious gap in academic and clinical literature by providing reviews which summarize and synthesize these findings. Topics considered and discussed include the possible biological and neuropsychological effects of trauma at different epochs and their effect on health. This book will be essential reading for psychiatrists, clinical psychologists, mental health professionals, social workers, pediatricians and specialists in child development.
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Prefrontal cortex provides both inhibitory and excitatory input to distributed neural circuits required to support performance in diverse tasks. Neurological patients with prefrontal damage are impaired in their ability to inhibit task-irrelevant information during behavioral tasks requiring performance over a delay. The observed enhancements of primary auditory and somatosensory cortical responses to task-irrelevant distractors suggest that prefrontal damage disrupts inhibitory modulation of inputs to primary sensory cortex, perhaps through abnormalities in a prefrontal-thalamic sensory gating system. Failure to suppress irrelevant sensory information results in increased neural noise, contributing to the deficits in decision making routinely observed in these patients. In addition to a critical role in inhibitory control of sensory flow to primary cortical regions, and tertiary prefrontal cortex also exerts excitatory input to activity in multiple sub-regions of secondary association cortex. Unilateral prefrontal damage results in multi-modal decreases in neural activity in posterior association cortex in the hemisphere ipsilateral to damage. This excitatory modulation is necessary to sustain neural activity during working memory. Thus, prefrontal cortex is able to sculpt behavior through parallel inhibitory and excitatory regulation of neural activity in distributed neural networks.
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Much effort has been made to understand the role of attention in perception; much less effort has been placed on the role attention plays in the control of action. Our goal in this chapter is to account for the role of attention in action, both when performance is automatic and when it is under deliberate conscious control. We propose a theoretical framework structured around the notion of a set of active schemas, organized according to the particular action sequences of which they are a part, awaiting the appropriate set of conditions so that they can become selected to control action. The analysis is therefore centered around actions, primarily external actions, but the same principles apply to internal actions—actions that involve only the cognitive processing mechanisms. One major emphasis in the study of attentional processes is the distinction between controlled and automatic processing of perceptual inputs (e.g., Shiffrin & Schneider, 1977). Our work here can be seen as complementary to the distinction between controlled and automatic processes: we examine action rather than perception; we emphasize the situations in which deliberate, conscious control of activity is desired rather than those that are automatic.
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Forgetting is often assumed to be a passive process. A program of research in theoretical memory is reviewed that shows how many instances of ordinary forgetting arise from active inhibitory processes that serve a very important attentional function: Selective retrieval. These inhibitory processes have been shown to cause long-lasting forgetting of “distracting” memories that interfere during our attempts to retrieve a particular fact or event. It is argued that these inhibitory processes may form the basis of some instances of traumatic forgetting, and that they provide a mechanistic account of an important phenomenon in the study of amnesia for childhood sexual abuse: the greater incidence of forgetting for betrayal traumas than for abuse perpetrated by Strangers.
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This study examines important developmental differences in patterns of activation in the prefrontal cortex during performance of a Go-No-Go paradigm using functional magnetic resonance imaging (fMRI). Eighteen subjects (9 children and 9 adults) were scanned using gradient echo, echo planar imaging during performance of a response inhibition task. The results suggest four general findings. First, the location of activation in the prefrontal cortex was not different between children and adults, which is similar to our earlier pediatric fMRI results of prefrontal activation during a working memory task (Casey et al., 1995). Second, the volume of activation was significantly greater for children relative to adults. These differences in volume of activation were observed predominantly in the dorsal and lateral prefrontal cortices. Third, although inhibitory processes have typically been associated with more ventral or orbital frontal regions, the current study revealed activation that was distributed across both dorsolateral and orbitofrontal cortices. Finally, consistent with animal and human lesion studies, activity in orbital frontal and anterior cingulate cortices correlated with behavioral performance (i.e., number of false alarms). These results further demonstrate the utility of this methodology in studying pediatric populations.
Connectionist models are used to explore the relationship between cognitive deficits and biological abnormalities in schizophrenia. Schizophrenic deficits in tasks that tap attention and language processing are reviewed, as are biological disturbances involving prefrontal cortex and the mesocortical dopamine system. Three computer models are then presented that simulate normal and schizophrenic performance in the Stroop task, the continuous performance test, and a lexical disambiguation task. They demonstrate that a disturbance in the internal representation of contextual information can provide a common explanation for schizophrenic deficits in several attentionand language-related tasks. The models also show that these behavioral deficits may arise from a disturbance in a model parameter (gain) corresponding to the neuromodulatory effects of dopamine, in a model component corresponding to the function of prefrontal cortex.
A theory of ironic processes of mental control is proposed to account for the intentional and counterintentional effects that result from efforts at self-control of mental states. The theory holds that an attempt to control the mind introduces 2 processes: (a) an operating process that promotes the intended change by searching for mental contents consistent with the intended state and (b) a monitoring process that tests whether the operating process is needed by searching for mental contents inconsistent with the intended state. The operating process requires greater cognitive capacity and normally has more pronounced cognitive effects than the monitoring process, and the 2 working together thus promote whatever degree of mental control is enjoyed. Under conditions that reduce capacity, however, the monitoring process may supersede the operating process and thus enhance the person's sensitivity to mental contents that are the ironic opposite of those that are intended.
Theories of the regulation of cognition suggest a system with two necessary components: one to implement control and another to monitor performance and signal when adjustments in control are needed. Event-related functional magnetic resonance imaging and a task-switching version of the Stroop task were used to examine whether these components of cognitive control have distinct neural bases in the human brain. A double dissociation was found. During task preparation, the left dorsolateral prefrontal cortex (Brodmann's area 9) was more active for color naming than for word reading, consistent with a role in the implementation of control. In contrast, the anterior cingulate cortex (Brodmann's areas 24 and 32) was more active when responding to incongruent stimuli, consistent with a role in performance monitoring.
It is controversial whether the dorsolateral prefrontal cortex is involved in the maintenance of items in working memory or in the selection of responses. We used event-related functional magnetic resonance imaging to study the performance of a spatial working memory task by humans. We distinguished the maintenance of spatial items from the selection of an item from memory to guide a response. Selection, but not maintenance, was associated with activation of prefrontal area 46 of the dorsal lateral prefrontal cortex. In contrast, maintenance was associated with activation of prefrontal area 8 and the intraparietal cortex. The results support a role for the dorsal prefrontal cortex in the selection of representations. This accounts for the fact that this area is activated both when subjects select between items on working memory tasks and when they freely select between movements on tasks of willed action.
Theories of cognition frequently assume the existence of inhibitory mechanisms that deactivate mental representations. Justifying this assumption is difficult because cognitive effects thought to reflect inhibition can often be explained without recourse to inhibitory processes. This article addresses the uncertain status of cognitive inhibitory mechanisms, focusing on their function in memory retrieval. On the basis of a novel form of forgetting reported herein, it is shown that classical associative theories of interference are insufficient as accounts of forgetting and that inhibitory processes must be at work. It is argued that inhibitory processes are used to resolve computational problems of selection common to memory retrieval and selective attention and that retrieval is best regarded as conceptually focused selective attention. (PsycINFO Database Record (c) 2012 APA, all rights reserved)