Implicit and explicit memory without awareness

Summary Three experiments are reported which investigate the conscious status of subjects during an implicit-memory test. In all experiments the subjects either named each visually presented target item or generated each item from an anagram in a first phase of incidental learning. In a second phase, they were either given a visual word-stem completion task as an implicit-memory test or given a recognition task (Experiment 1), or a cued-recall task (Experiments 2 and 3) as explicit-memory tests. Finally, in a third phase the subjects were required to make decisions about the input status (i. e., they had to decide whether the item was present in the first phase) as well as about the output status of information (i. e., they had to decide whether the item had been completed, recognized or recalled in the second phase). A generation effect (i. e., generated items were remembered better than named items) was evident in the recognition and recall data, but only for items whose recognition or recall was accompanied by conscious recollection of their previous occurrence in the study list. Judgments about the input status were more precise, given that items had been consciously recognized or recalled rather than completed. The same pattern of findings was observed for judgments about the output status. The results are interpreted as evidence that subjects in implicit-memory tests are less aware of the fact that some of their productions are relevant to prior experiences. In addition, they are less aware of the fact that they are retrieving information from their memories. However, the same state of nonawareness may be present in explicit-memory tests, as was revealed by the performance of subjects on those items whose recognition or recall was not accompanied by conscious recollection.     

Implicit and explicit memory bias in anxiety

Previous investigations of recall and recognition for threatening information in clinically anxious subjects have yielded equivocal results. The present study contrasts implicit (word completion) with explicit (cued recall) memory and shows that indices of bias for emotional material derived from the two types of memory are independent of one another. The explicit measure was correlated with trait anxiety scores, but did not clearly distinguish between subjects with clinical anxiety states and normal control subjects. On the implicit memory measure, clinically anxious subjects produced more threat word completions, but only from a set to which they had recently been exposed. These results are taken as evidence that internal representations of threat words are more readily or more persistently activated in anxiety states, although they are not necessarily better elaborated.     

Implicit and explicit memory for visual patterns

The article reports an investigation of implicit and explicit memory for novel, visual patterns. Implicit memory was assessed by a speeded perception task, and explicit memory by a four-alternative, forced-choice recognition task. Tests were given either immediately after testing or 7 days later. The results suggest that a single exposure of a novel, nonverbal stimulus is sufficient to establish a representation in memory that is capable of supporting long-lived perceptual priming. In contrast, recognition memory showed significant loss over the same delay. Performance measures in the two tasks showed stochastic independence on the first trial after a single exposure to each pattern. Finally, a specific occurrence of a previously studied item could be retrieved from explicit memory but did not affect the accuracy of perception in the implicit memory test. The results extend the domain of experimental dissociations between explicit and implicit memory to include novel, nonverbal stimuli.     

Implicit and explicit memory for compound words

Subjects studied visually presented compound words (e.g.,toothpaste, heartache) and then received a recognition, perceptual identification, or word-fragment completion test that contained old, recombined (e.g.,toothache), and partially and completely new words. False recognitions increased with the increasing number of previously studied components; however, priming in perceptual identification occurred only for old words. Priming in word-fragment completion occurred for old and recombined words. Reducing the time available to solve word fragments, from 20 sec to 5 sec, did not affect the pattern of results; it is therefore unlikely that priming for recombined words resulted from the use of a recollection-based strategy. Memory tasks that involve a conceptual component access memories that are constructed from parts; memory tasks that are primarily perceptual do not access such memories.     

Implicit memory bias,explicit memory bias,and anxiety

Abstract

Normals high, medium, and low in trait anxiety performed two encoding tasks (one predominantly data-driven and the other conceptually driven) on threat-related and neutral words, followed by tests of word completion, cued recall, and free recall. Memory performance indicated the existence of negative memory biases in the high trait-anxious group, but it was generally not possible to decide whether the biases were associated with trait anxiety rather than with depression. The biases were obtained mainly when there was a match between the processes at encoding and those at the time of test, whether the matching processes were predominantly data-driven or conceptually driven. Implications of these findings for implicit and explicit memory biases associated with high trait anxiety are discussed.     

Implicit and explicit memory in young and older adults

In three experiments, young and older adults were compared on both implicit and explicit memory tasks. The size of repetition priming effects in word completion and in perceptual identification tasks did not differ reliably across ages. However, age-related decrements in performance were obtained in free recall, cued recall, and recognition. These results, similar to those observed in amnesics, suggest that older adults are impaired on tasks which require conscious recollection but that memory which depends on automatic activation processes in relatively unaffected by age.     

Implicit and explicit memory for odors: Hemispheric differences

In two experiments, implicit and explicit tests were used to investigate the lateralization of odor memory. Odors were at all times presented monorhinically. At test, odors were presented to either the ipsi- or the contralateral side of the nostril used for inspection. In Experiment 1, participants were first primed to a set of odors. At test, response latencies for odor identification were measured. The results were that priming odors tested via the left but not the right nostril were identified faster than control odors. In Experiment 2, a similar design probed episodic recognition memory. Memory performance did not differ between the left and right nostrils, but the measures of response latency favored the right side. The study demonstrates that it is possible to tap differences in memory performance between the cerebral hemispheres through monorhinic presentation of odors in healthy persons, and that these differences depend on the test nostril rather than the inspection nostril.     

Implicit and explicit memory bias in depressed and non depressed subjects

Abstract

Two experiments were carried out to investigate a possible mood-congruent memory bias in explicit memory (free-recall test) and implicit memory (word-stem completion task) for positive and negative words in depressed and non depressed college students. A comparison of implicit and explicit mood-congruent memory bias should help to reveal cognitive processes involved in this effect. The results of both studies indicated that depressed subjects showed a memory bias not only on the traditional explicit memory task, but on the implicit memory task as well. The theoretical implications of these results are discussed.     

Implicit and explicit memory for affective passages in temporal lobectomy patients

Eighteen temporal lobectomy patients (9 left, LTL; 9 right, RTL) were administered four verbal tasks, an Affective Implicit Task, a Neutral Implicit Task, an Affective Explicit Task, and a Neutral Explicit Task. For the Affective and Neutral Implicit Tasks, participants were timed while reading aloud passages with affective or neutral content, respectively, as quickly as possible, but not so quickly that they did not understand. A target verbal passage was repeated three times; this target passage was alternated with other previously unread passages, and all passages had the same number of words. The Explicit Affective and Neutral Tasks were administered at the end of testing, and consisted of multiple choice questions regarding passage content. Verbal priming effects in terms of improved reading speed with repetition for the target but not non-target passages were found for patients with both left and right temporal lobectomies. As in the Burton, Rabin et al. [Burton, L., Rabin, L., Vardy, S.B., Frohlich, J., Wyatt, G., Dimitri, D., Constante, S., Guterman, E. (2004). Gender differences in implicit and explicit memory for affective passages. Brain and Cognition, 54(3), 218-224] normative study, there were no interactions between this priming effect and affective/neutral content. For the explicit tasks, items from the repeated passages were remembered better than the unrepeated passages, and there was a trend for information from the affective passages to be remembered better than the neutral passages, similar to the normative pattern. The RTL group did not show the normative pattern of slower reading speed for affective compared to neutral passages that the LTL group showed. Thus, the present findings support the idea that intact right medial temporal structures are important for affective content to influence some aspects of verbal processing.     

Implicit and explicit memory for new associations in normal and amnesic subjects

Two experiments examined whether repetition priming effects on a word completion task are influenced by new associations between unrelated word pairs that were established during a single study trial. On the word completion task, subjects were presented with the initial three letters of the response words from the study list pairs and they completed these fragments with the first words that came to mind. The fragments were shown either with the paired words from the study list (same context) or with other words (different context). Both experiments showed a larger priming effect in the same-context condition than in the different-context condition, but only with a study task that required elaborative processing of the word pairs. This effect was observed with college students and amnesic patients, suggesting that word completion performance is mediated by implicit memory for new associations that is independent of explicit recollection.     

Implicit and explicit memory bias for threat in post-traumatic stress disorder.

We investigated explicit (cued recall) and implicit (word completion) memory in Vietnam combat veterans with (n = 24) and without (n = 24) post-traumatic stress disorder (PTSD). Half of the subjects in each group encoded combat, social threat, positive, and neutral words elaboratively, whereas the others encoded these words nonelaboratively. On the cued recall test, under both encoding conditions, both groups recalled more combat words than other words. However, difference scores obtained by subtracting the mean recall for neutral words from the mean recall scores for the other words revealed that PTSD patients exhibited a relative explicit memory bias for combat words. That is, PTSD patients tended to exhibit poor memory for everything but combat words. On the word completion test, only PTSD subjects exhibited an implicit memory bias for combat words. This bias was greater for primed than for unprimed words, thereby ruling out a response bias. Such memory bias may underlie the 'reexperiencing' symptoms characteristic of PTSD (e.g. intrusive thoughts, nightmares).     

High-risk students in junior college: a special program

The college student who is considered a “high academic risk” offers to teachers, counselors, and curricula a great challenge. Most “bright” students have to exert little effort to achieve academic successs; however, there are other students for whom learning comes only with great personal effort, as well as great patience and concern on the part of their instructors, who can also benefit from higher education. The results of Project speed , representing one attempt to do something with high-risk students, strongly suggest that developmental programs can have a measurably positive influence upon their participants.     

Implicit and explicit memory performance in children with attention deficit/hyperactivity disorder

The present investigation examined implicit and explicit memory in 20 children diagnosed with attention deficit/hyperactivity disorder (AD/HD) and 20 matched controls. Consistent with previous research, children with AD/HD performed more poorly than controls on an explicit test of long‐term memory for pictures. New results were that (a) there was no deficit on an implicit memory test for equivalent material and that (b) the observed deficit in explicit memory operated over and above any effects of depression/anxiety. Another finding to emerge was that AD/HD children had greater difficulty than controls in identifying pictures of objects that were presented in an unusual form, either rotated or degraded. Overall, the pattern of results is interpreted in terms of deficient effortful/resource‐intensive processes in AD/HD but intact automatic processes.     

Poly‐victimization and executive functions in junior college students

This study sought to characterize executive dysfunctions in poly‐victimized students without posttraumatic stress disorder (PTSD) symptoms and the relationship between neuropsychological and behavioral rating measures of executive functions (EFs). Based on self‐report data of exposure to victimization and PTSD symptoms, 259 junior college students aged 18–21 years were classified into four groups: poly‐victimization with PTSD symptoms (PVP), poly‐victimization without PTSD symptoms (PVnP), non‐poly‐victimization (nPV), and non‐victimization (nV). Respondents also completed the Behavior Rating Inventory of Executive Function‐Adult Version (BRIEF‐A). Of the 259 participants, 131 were administered a battery of neuropsychological tests from the Cambridge Neuropsychological Testing Automated Battery (CANTAB). The PVP group and the PVnP group performed worse than the nV group on most BRIEF‐A scales. When compared with the nPV group, the PVP group demonstrated poorer performance on the scales of Inhibit, Shift, Emotional Control, Initiate, and Working Memory, while the PVnP group performed more poorly on the Working Memory scale and the Task Monitor scale. For all BRIEF‐A scales, no significant differences were detected between the PVP group and the PVnP group. This study showed no between‐group differences for most of the neuropsychological tests except for the Stop Signal Task (SST), and no correlations between these two measures of EFs. Overall, we found evidence of an association between deficits in EFs and poly‐victimization. Although our study raises questions about the relationship between these two measures of EFs, it suggests that the use of the BRIEF‐A in conjunction with the CANTAB provides a more complete assessment of the executive dysfunctions.     

New approaches to understanding unconscious processes: Implicit and explicit memory systems

Abstract

Freud viewed the unconscious as being roughly equivalent to dynamically repressed wishes, needs, and motivations. Findings from developmental psychology, cognitive psychology, psychoanalysis, and neuroscience over the past 40 years have dramatically changed our views of unconscious processes and the human mind. It is now clear that Freud's dynamic unconscious is only a minor segment of information that is processed at subsymbolic, implicit, and automatic levels. Only a fraction of this information is further processed at explicit conscious levels. Moreover, the vast majority of the information that remains nonconscious is adaptive and has major consequences for development. We examine some clinical implications of these views.     

Implicit and explicit memory: Implications for the symbol-manipulation versus connectionism controversy

Summary This paper deals with three issues. First, the symbol-manipulation versus connectionism controversy is discussed briefly. Both can be seen as formalisms or languages for describing human behavior, but it is argued that these languages are not fully equivalent. The importance of the ability of connectionist models to learn autonomously, often underestimated, allows them to perform tasks that may defy formalization. Secondly, the structural and functional characteristics of a new connectionist learning model are presented. It avoids some of the psychological and biological implausibilities of currently popular models and solves some of the problems and shortcomings of these models. Thirdly, some simulation results are presented. The model successfully simulates the dissociation between explicit and implicit memory performance as found in patients with anterograde amnesia. This simulation provides an example of the advantages of using the connectionist language in the domain of memory psychology. It is also a good example of how psychological evidence can be used to improve connectionist models.The second author is supported by the Dutch Organization for Scientific Research (NWO)     

Implicit and explicit tests of odor memory reveal different outcomes following interference

Experiencing two odors as a mixture can later increase their perceived similarity when presented separately. Such an increase in similarity can be used as an implicit measure of how well participants remember the mixture. Three experiments tested the resistance to interference of this effect by first giving participants exposure to two 2-odor mixtures and then presenting each odor from one mixture (interfered pair) separately many times. After the latter interference phase, participants rated the similarity of the two odors in each pair. The experiments varied in terms of the number of initial exposures to the mixtures, the number of odor presentations in the interference phase, and the control conditions employed. No difference in similarity ratings for the interfered and non-interfered pair was found in any experiment. In contrast to the lack of interference with this implicit measure, an explicit measure of memory based on participants’ ratings of odor frequency revealed that they could recall to some degree that the interfered odors had been presented alone in the second phase. These results suggest that implicit memory for odor mixtures is highly resistant to interference and is consistent with a configural encoding account of this effect.     

Attention and memory biases for aggressive information in college students with fragile high self-esteem

In this study, we examined attention and memory biases for aggressive information in two groups of college students. Individuals with fragile high self-esteem (n = 30) and individuals with secure high self-esteem (n = 30) first performed a dot-probe task investigating attention bias, followed by a memory task. Incidental free recall of words presented in the memory task was then completed to assess memory bias. Results revealed that individuals with fragile high self-esteem exhibited significant attention and memory biases for aggressive words compared with secure high self-esteem individuals. Attention bias for aggressive words was positively correlated with memory bias in individuals with fragile high self-esteem, but no correlation was found for individuals with secure high self-esteem. These findings suggest that individuals with fragile high self-esteem selectively attend to and remember aggression-related information. They may process information in ways that are congruent with an aggression-related schema. This study reveals the aggressive cognitive processes of individuals with fragile high self-esteem, which may be related to aggression.     

Measurement of social-evaluative anxiety in junior high school students

This paper provides some initial normative and validity data on the Social Avoidance and Distress (SAD) and the Fear of Negative Evaluation (FNE) scales for junior high school students. Findings indicated: the level of social-evaluative anxiety does not significantly vary during the junior high school years or between sexes, junior high school students report similar levels of FNE to college students but less SAD, a significant positive correlation between treatment subjects' SAD scores and peer sociometric ratings of social-evaluative anxiety, and subjects treated for social anxiety reported significantly less SAD and FNE at follow-up assessment. Recommendations for future research and clinical use of the SAD and FNE are offered.