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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Stimulus property effects on cue competition and temporal estimates during causal learning

Spoor, Willemijn Magda Elly Maria January 2013 (has links)
Learning and timing models have developed along different trajectories within psychology; however, more recent theorising has speculated that both of these phenomena might be modelled within a single theoretical model. While such an approach has merit, the majority of studies into how learning and timing interact have employed nonhuman subjects. Consequently, little is known about how these core psychological processes might interact in humans; this body of experiments was, conducted in order to investigate this issue. Experiments were run to test the hypothesis that cue competition attenuates the ability of participants to estimate a stimulus’ temporal parameters. By studying whether temporal estimates differed between cues in conditions in which blocking and overshadowing was predicted to be weaker or stronger, it could be determined whether time and association were encoded together. In a series of causal learning experiments participants were trained with a cue competition paradigm. On test both cue competition and temporal estimates were examined. The results showed that participant instructions influenced cue competition and that cue properties could influence blocking and overshadowing in specific cases. Temporal estimates made by participants were influenced by cue properties: less accurate estimates of target cue duration were made in several experiments, and temporal estimates between groups varied when blocking and overshadowing were constant. Existing associative learning theories could predict blocking and overshadowing, but could not predict the temporal results. Timing models, for example, the SET model, failed to predict temporal results. To conclude, the results suggest that timing is not encoded as part of the association.

Control and maintenance processes in working memory : neuropsychological investigations

Moro, R. January 2008 (has links)
The aim of this thesis was to investigate working memory by investigating performance on an updating task devised to pose variable demands on maintenance and control processes. The task required participants to recall information that was "relevant" according to a given criterion, at the same time inhibiting information that was not relevant to that criterion. Performance on this task was investigated in healthy participants, in order to understand the impact of different loads on maintenance and inhibition processes, and of different stimuli on recall performance and on error production. The predictions tested were that recall performance on the updating task would be affected by both load on maintenance and load on control processes and that the production of errors due to the recall of "to-be-inhibited" information would only be affected by load on control processes. The hypothesis that the central executive component of working memory would be differentially affected by normal aging, dementia of the Alzheimer's type and brain damage affecting the prefrontal lobes was also explored by investigating performance on the updating task in groups with these characteristics. The predictions were that in normal ageing maintenance would be reduced but control processes would be spared, in senile dementia both processes would be impaired and in presence of prefrontal damage only control processes would be affected. Moreover, since the multi-component model of working memory was originally conceived as the basis for complex cognitive abilities such as mental arithmetic, this was also investigated in groups of participants reported in the literature as having problems in these functions as well as in working memory. The findings are discussed in light of the predictions.

Effects of Visual Working Memory (VWM) load and selective attention on recognition memory for unfamiliar faces

Onwuegbusi, Tochukwu Ojiakonobi January 2015 (has links)
When we look around, our subjective impression is of a highly detailed visual representation, which allows us to perceive changes in the identity and location of the objects and people around us. However, research has shown that this impression is misleading; the acuity and amplitude of visual sensory information varies across space and time and is subject to numerous post-perceptual filters. Among these, Visual Working Memory (VWM) is a limited capacity, transient store for visual information that supports the continuity of sensory experience. Selective visual attention protects VWM capacity by filtering relevant from irrelevant visual information during the encoding and maintenance of remembered objects. The aim of this thesis was to provide insights into the way in which capacity limits in VWM interact with selective attention to predict recognition accuracy for unfamiliar faces. In order to explore this issue, a Change detection paradigm was used to assess the relationship between memory load (set size) and d’ (an index of discriminability derived from Signal detection theory), while manipulating target-distractor similarity, mode of stimulus presentation, visual attention and eye movement. The results of six experiments yielded four key findings: (1) the sensitivity of recognition memory for unfamiliar faces is independently affected by the similarity and number of faces to remember, (2) stimulus-driven shifts of attention bias the allocation of VWM resources when multiple to-be-remembered (TBR) faces compete for selection, (3) the biasing signals that mediate competition between faces operate independently of the resolution of the information available to the observer, and (4) the sensitivity of recognition memory for unfamiliar faces is mediated by emotional valence. Taken together, these findings suggest that selective attention and VWM interact to mediate the accuracy of recognition memory for unfamiliar faces in a number of different situations.

Memory recall performance in emotional contexts: cognitive and physiological investigations

Christoforou, Eugenia January 2014 (has links)
This thesis was devoted to the investigation of how emotionally pleasant, unpleasant and neutral in valence contexts influence memory recall performance for neutral words presented in such contexts, and whether the physiological technique of measuring finger skin temperature can differentiate emotional valence. The plethora of research studies investigating the effects of emotion on memory performance have focused on emotional content of high arousal and not context. Thus, up to now there is limited existing empirical evidence concerning the relationship of memory recall performance and emotional contexts. In addition, the practical value of using the physiological measurement of finger skin temperature proposed for identifying emotional valence has not been extensively investigated. In five studies, employing a repeated measures experimental design, volunteers with an age range of 21 - 45 years offered the collection of data with the use of memory free recall tests and measurements of their finger skin temperature. Based on a dimensional approach to emotion, contexts were chosen to be pleasant, unpleasant, and neutral in emotional valence and not of extreme arousal, and words were neutral in valence and not arousing. Finger skin temperature was initially analysed using five different measurements in order to detect the most appropriate measurement to assess its relationship to emotional valence of contexts. Memory recall performance appeared to be better facilitated in both induced and perceived neutral contexts, then in pleasant and least facilitated in unpleasant contexts. The mean and linear regression of finger skin temperature, were selected as the most appropriate physiological measurements for this set of studies. Finger skin temperature was constant during periods of no stimulation and indicated physiological differentiation across emotional contexts. There was no replicated statistically significant physiological differentiation of emotional valence based on the finger skin temperature during the emotionally pleasant, unpleasant and neutral contexts.

Instruction based manipulation of memory confidence and perceived responsibility in a non-clinical sample and its effects on checking behaviour and memory task performance

Murray, Sara January 2014 (has links)
Individuals with Obsessive-Compulsive Disorder (OCD), specifically checking compulsions (CC), report they check because they doubt their memory ability. Repeated checking, however, appears to perpetuate checking behaviour and further enhances uncertainty over memory ability. It is unclear if a memory deficit underlies CC or whether beliefs about one's memory ability initially induce CC. Beliefs about one's metamemory (specifically low memory confidence: LMC) and a high sense of responsibility (HR) over preventing harm have separately been associated with CC. However, the influence of LMC and HR together have not causally been linked to actual checking or memory performance as yet. Therefore the current study manipulated healthy participants' (n= 61) memory confidence by providing either positive or negative false feedback on performance in a memory task involving presentation of verbal and visual items. Furthermore, high or low responsibility feedback was given to manipulate sense of responsibility. Performance (memory accuracy and response bias) and memory confidence for tasks on an actual recognition test were measured, in addition to checking behaviour (urge to check and actual checking). Results revealed that the manipulations did not affect urge to check but did affect memory confidence, specifically numerically enhancing actual checking of verbal stimuli in LMC groups. Memory accuracy was better for easier visual tasks but also response bias was more liberal for verbal items in LMC groups. The responsibility manipulation appeared to be ineffective. Thus metamemory beliefs may induce checking behaviour and affect memory task performance. Limitations of the study and the roles of task difficulty and response bias are discussed in relation to CC experimental investigations, but also regarding cognitive behavioural formulations and treatments of OCD.

Balanced time perspective as a mediator of the relationship between mindfulness and subjective well-being: a cross sectional study

Perman, Gemma January 2014 (has links)
Objectives: Time perspective refers to a process that attempts to make sense of everyday experience by drawing on memories, present experiences and predicted future outcomes (Zimbardo & Boyd, 1999). A time perspective that is more balanced and able to flexibly move between time orientations (i.e. past, present, future) is hypothesized to be more adaptive than one that is dominated by one time orientation. Previous research has found that both mindfulness and balanced time perspective are associated with greater subjective well-being. The present study examined whether balanced time perspective mediated the positive relationship between mindfulness and subjective well-being (SWB). Method: A cross-section~l online questionnaire design was employed. Two hundred and seventy five participants completed measures of mindfulness (Five Facets of Mindfulness Questionnaire short-version), time perspective (Zimbardo's Time Perspective Inventory) and cognitive and emotional indicators of SWB (Satisfaction With Life Scale; Scale of Positive and Negative Experience). Results: Pearson's correlation coefficients revealed that higher levels of mindfulness were significantly associated with greater SWB and balance in time perspective profiles. Greater balance in time perspective profiles was significantly associated with greater SWB. Balanced time perspective was found to be a mediator of the relationship between mindfulness and SWB. Evidence for an additional mediation pathway was found, and suggested that higher levels of mindfulness positively influences SWB, through decreasing levels of the time perspective dominated by a past-negative orientation. Conclusions: Although the cross-sectional design limits causality conclusions, these findings suggest that the development of mindfulness may positively influence SWB, through promoting balance in time perspective profiles or through decreasing the negative influence that a time perspective dominated by the past-negative orientation has on SWB. The clinical implications of these findings for SWB enhancing interventions are outlined.

Intrusive memories, coping and outcome in depression : towards a traumatic processing model?

Parker, Julie Diane January 1997 (has links)
Recent studies (e.g. Kuyken & Brewin, 1994a) have noted the presence of high levels of disturbing intrusive memories in depressed women. Intrusive memories are best known as a post-traumatic symptom and have received considerable attention from researchers in this field. The presence of a post-traumatic symptom in depression indicates that trauma models might be useful in refining our understanding and treatment of depression. Predictions based on theories of post-traumatic processing were tested in relation to the intrusive memories of a sample of 26 depressed women. The women showed a pattern of intrusive memory experiences which indicate that their memories are likely to be traumatic in nature. The equal availability of childhood and adulthood memories to depressed women contrasts the pattern observed in the 12 control participants, and in other non-clinical samples (e.g. Berntsen, 1996), and is interpreted as lending support to theoretical models of depression which emphasise the importance of childhood experiences to adult depression. The coping strategies deployed to deal with negative intrusive memories were assessed in both groups. The clinical group showed greater use of avoidant coping than controls, in line with predictions derived from the literature regarding coping and depression. The predictive power of coping style for outcome of depression and intrusion was tested by following up 20 of the 26 depressed participants, approximately four months after initial assessment. The data indicate that the use of approach coping, specifically of Positive Reappraisal, in relation to intrusive memories was significantly predictive of better outcome of depression. This finding is interpreted in the context of psychodynamic models of depression. The data also indicate that the use of avoidant coping, specifically of Cognitive Avoidance, is significantly predictive of the maintenance of disturbing intrusions. This finding is interpreted in the context of traumatic processing models. Finally, predictions based on the conceptualisation of dissociation as an avoidant coping mechanism, used to keep traumatic affects and experiences out of consciousness, were tested. Dissociation did not show the pattern of associations predicted, but rather seemed to be more closely allied with passive resignation than active avoidance. The pattern of results obtained in this study are interpreted as lending support to the conceptualisation of depression as a trauma-related disorder, and also as lending support to theoretical models which assign great importance to childhood experiences in the aetiology of adult disorder. Potential implications of the study for clinical practice are discussed, and suggestions made for future research.

Unfamiliar face recognition : how we perceive and remember new faces

Zimmermann, Friederike Gisela Sophie January 2013 (has links)
Most humans are experts in recognizing faces of familiar individuals, but are poor at individuating unfamiliar faces. The discrepancy between these two types of face recognition suggests qualitative differences in the perceptual encoding and memory storage of familiar and unfamiliar faces, yet little is known about the neural basis of these differences. In the present thesis, behavioural and event-related brain potential (ERP) measures were combined to investigate the mechanisms that underlie the perception and recognition of unfamiliar faces. The first two experiments investigated whether memory traces for unfamiliar faces are based on low-level view-dependent or more high-level view-independent codes. Results provide strong evidence for a qualitative change from strictly view-dependent to view-independent representations in visual face memory as initially novel unfamiliar faces become more familiar. A second series of three experiments examined whether identity-specific cues are processed in an optional or obligatory fashion. Findings suggest that the perception of facial identity is strongly task-dependent (i.e., optional), even for famous faces, but can also show a degree of mandatory processing when identity is task-irrelevant. The sixth study examined the persistence of perceptual memories of unfamiliar faces and revealed a substantial weakening of face representations in visual working memory over short periods of time. The final experiment investigated the neural basis of developmental prosopagnosia (DP). Results demonstrated spared identity-sensitive processing in DP participants, indicating that their face recognition deficits do not always result from severely disrupted visual face recognition processes. However, despite evidence for perceptual learning of invariant aspects of face structure, these processes seemed to be inefficient in individuals with DP. Taken together, this thesis explored how we perceive and remember individual unfamiliar faces. Results indicate that unfamiliar face recognition is mediated by fast and flexible (i.e., strongly task-dependent) identity-specific visual processes, which rapidly become view-invariant during face learning.

Memory interference and the benefits and costs of testing

Potts, R. January 2014 (has links)
Testing often enhances memory, but memory can be harmed by interference from similar or competing items. This thesis examines two situations in which it has been proposed that testing can be harmful to memory because the test itself increases susceptibility to interference. Experiments 1-8 investigate the effect of generating errors during new learning. Participants learned definitions for unfamiliar English words, or translations for foreign vocabulary, either by generating a response and being given corrective feedback, by reading the word and its definition, or by selecting from a choice of definitions followed by feedback. In a final test of all words, generating errors followed by feedback led to significantly better memory for the correct definition than either reading or making incorrect choices, suggesting that the benefits of generation are not restricted to correctly generated items. Even when information to be learned is novel, errorful generation may play a powerful role in potentiating encoding of corrective feedback. Metacognitive judgments of learning revealed that participants were strikingly unaware of this benefit, judging errorful generation to be a less effective encoding method than reading or incorrect choosing, when in fact it was better. Predictions reflected participants’ subjective experience during learning. A second series of experiments (Experiments 9-10) examines the claim that reactivating a consolidated memory destabilizes it, making it more susceptible to interference from new learning. Participants learned English-Swahili word pairs (List 1) on Day 1 with a final test on Day 3. When memory of List 1 was reactivated in the form of a reminder test immediately before learning Finnish words (List 2) on Day 2, testing, far from impairing List 1 memory, enhanced it, revealing a testing effect. Furthermore, List 2 learning disrupted List 1 memory when there was no reminder test, but reminder testing immunized the memory against interference.

Physicochemical models of the memory storage process : the historical role of argument from analogy

Colville-Stewart, S. B. January 1976 (has links)
No description available.

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