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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.
11

How memory of the past, a predictable present and expectations of the future underpin adaptation to the sound environment

Nöstl, Anatole January 2015 (has links)
By using auditory distraction as a tool, the main focus of the present thesis is to investigate the role of memory systems in human adaptation processes towards changes in the built environment. Report I and Report II focus on the question of whether memory for regularities in the auditory environment is used to form predictions and expectations of future sound events, and if violations of these expectations capture attention. Collectively the results indicate that once a stable neural model of the sound environment is created, violations of the formed expectations can capture attention. Furthermore, the magnitude of attentional capture is a function of the pitch difference between the expected tone and the presented tone. The second part of the thesis is concerned with, (a) the nature (i.e. the specificity) of the neural model formed in an auditory environment and, (b) whether complex cognition in terms of working memory capacity modulates habituation rate. The results in Report III show that the disruptive effect of the deviation effect diminishes with the number of exposures over time, and also as a function of working memory capacity. The aim of Report IV was to investigate the nature (and specificity) of the neural model formed in an auditory environment. If the neural model is fashioned around a specific stimulus then an observable increase of response latency should occur in conjunction with the deviant change. The results in Experiment 1 in Report IV, however, show that the habituation rate remained the same throughout the experiment. To further test the specificity of the neural model the modalityof the deviant event was switched (from auditory to visual and vice versa) in Experiment 3 in Report IV. The collective findings indicate that the formed neural model may be of a more general nature than previously suggested. The aim of Experiment 2 in Report IV was to investigate what properties of the sound environment underpin habituation rate, more specifically if predictability of a deviant trial facilitates the habituation process. The finding that the habituation rate was similar whether there was a fixed temporal interval between the deviant trials or a random interval suggests that the amount of occurrences (i.e. number of deviant trials) determines habituation rate, not the predictability of a deviant trial. / Denna avhandling undersöker vilken roll minnessystem har i anpassningen till förändringar i den byggda miljön. Delrapport I och Delrapport II fokuserar på frågan om regelbundenheter i den auditiva miljön används för att skapa förväntningar och prediktioner gällande framtida händelser, och vidare, om avvikelser från dessa förväntningar fångar uppmärksamheten. Sammantaget tyder resultaten på att uppmärksamheten fångas om nämnda förväntningar inte infrias. Vidare visar resultaten att magnituden av den fångade uppmärksamheten är en funktion av skillnaden mellan den förväntade tonen och den presenterade tonen. Den andra delen av avhandlingen undersöker (a) karaktären (dvs. specificiteten) av den neurala modellen och (b) om komplex kognition i termer av arbetsminneskapacitet påverkar habituation. Resultaten i Delrapport III visar att den störande effekten av den avvikande tonen minskar dels med antalet exponeringar och dels som en funktion av arbetsminneskapacitet. Syftet med Delrapport IV var att undersöka hur specifik den skapade neurala modellen är. Resultaten i Experiment 1 i Delrapport IV visar att habituationstakten förblev densamma under hela experimentet även om den avvikande tonen byttes ut under experimentets gång. Detta tillsammans med resultaten i Experiment 3 i Delrapport IV, där habituation kunde påvisas även om modaliteten av den avvikande händelsen byttes från auditiv till visuell och vice versa, indikerar att den neurala modellen är av en mer allmän karaktär än vad man tidigare trott. Syftet med Experiment 2 i Delrapport IV var att undersöka vilka egenskaper i ljudmiljön som påverkar habituationstakten. Upptäckten att takten var likvärdig oavsett om det fanns ett fast eller ett slumpmässigt intervall mellan de avvikande tonerna tyder på att det är mängden förekomster (dvs. antalet avvikande toner), snarare än predicerbarhet, som avgör habituationstakten.
12

The neural mechanisms of attention : exploring threat-related suppression and enhancement using ERPs

Bretherton, Paul January 2016 (has links)
The capacity of the visual system to process information about multiple objects at any given moment in time is limited. This is because not all information can be processed equally or in parallel and subsequently reach consciousness. Previous research has utilized behavioural experiments to explore visual attention. More recently research, however, has used electroencephalography (EEG) to measuring the electrical brain activity in the posterior scalp. By time locking visual stimulus events to fluctuations in scalp activity researchers have been able to estimate the time course of attentional changes by measuring changes in these event-related potentials (ERP). One component in particular (N2pc) has been a reliable tool in measuring either the suppression of, or the shift of attentional to, both ignored and attended items in the visual scene. The N2pc is measured by comparing the ERP activity contralateral and ipsilateral to the visual field of interest. More recently, evidence has been presented that the mechanisms of attention thought to be represented by the N2pc (suppression and attentional selection) could be separated into different ERP components (Pd: indexing attentional suppression of an ignored item; and Nt: indexing attentional selection of the target) and measured independently. In six experiments, using ERPs, this thesis employs these components to explore the mechanisms and strategies of the human attentional system. Additionally, this thesis focuses on the impact of different types of simultaneous processing load on the attentional system and how the mechanisms of this system are influenced. Experiment 1 explores the idea that the type or valence of information to be ignored may influence the ability to suppress it. Results of this experiment 4 show that neither the type nor valence of the irrelevant information modulated the amplitude of the distractor positivity (Pd), indicating suppression of the irrelevant distractor was not altered. Noted in experiment 1 was also the presence of an early negativity (Ne) that appeared to represent attentional capture of the ignored lateral stimulus. Experiment 2 demonstrated that the valence of the lateral target did not alter the target negativity (Nt), indicating a different pattern of results between the Nt and the N2pc reported in previous studies (e.g. Eimer & Kiss, 2007; Feldmann-Wüstefeld et al., 2010). Experiment 2 also showed a similarity of the target negativity (Nt) to the early negativity (Ne; the N2pc like component observed in exp 1) toward face and non-face stimuli. This comparison supported the idea that the early negativity (Ne) reflected attentional capture of the ignored lateral distractor and as a result was relabelled the distractor negativity (Nd) in subsequent experiments. Experiment 3 showed that the salience of the lateral image did not modulate the Pd as should be the case if the Pd reflected sensory-level processing. An early contralateral negativity (similar to the Nd observed in exp 1) was altered by the salience of the distractor which added support to the hypothesis that this reflects attentional capture of the lateral ignored image. Experiment 4 attempted to manipulate working memory (WM) to assess the effect of WM load on attentional capture and suppression. While the results did indicate modulation of suppression under WM load, the limitations of the design of experiment 4 made any definitive interpretation of the results unreliable. The results of experiment 5 showed that suppression, as indexed by the Pd, was not altered by cognitive load. However, reductions in attentional capture under high cognitive load, as indexed by the distractor negativity (Nd), were observed and contradict the results of previous experiments (c.f. Lavie & De Fockert, 2005) 5 where cognitive load resulted in an increase in attentional capture. Although, there appears to be some issue in the authors interpretation of the results of these experiments (see chapter 6 for discussion). The results of Experiment 6 show the opposite effect with a significant increase in the laterality of the Pd under high perceptual load. A similar increase in the laterality of the Pd was not reflected in terms of valence though, where suppression of threat related distractors was not altered under high perceptual load. The hypothesis that an increase in perceptual load will result in a decrease in attentional capture was generally supported by the results of experiment 6. Under high perceptual load angry face distractors captured attention, as indexed by the laterality of the Nd, with neutral face distractors showing a reduction in attentional capture. While under low perceptual load, both angry and neutral face distractors resulted in a significant (and similar) laterality of the Nd. The thesis concludes by discussing issues concerning Lavie’s Load Theory of attention and outlines some potential misinterpretations of previous data that have led to the proposal that cognitive load results in a decrease in attentional resources and therefore a decrease in attentional capture of ignored stimuli. It is argued in this thesis that the results of Lavie and de Fockert (2005), which concluded that the increase in cognitive load resulted in a decrease in attentional capture, are more likely to be due to changes in attentional capture (i.e. a reduction) and changes in RT (i.e. an increase), under cognitive load being separate responses to the availability of resources, one that focusses attention on the goal directed task and the other that results in extended processing time to carry out the more difficult task. In this case both ‘changes’ appear to work to prioritise resources in favour of the goal directed task.
13

Rôle des boucles cortico-ganglions de la base sur l'attention visuelle : effets de la stimulation dopaminergique et du noyau subthalamique dans la maladie de Parkinson / Role of the cortico-basal ganglia loops in visual attention : effects of dopaminergic and subthalamic nucleus stimulation in Parkinson's disease. / Ruolo dei circuiti cortico-sottocorticali nell’attenzione visiva : Effetti della stimolazione dopaminergica e del nucleo subtalamico nella malattia di parkinson

Tommasi, Giorgio 16 May 2011 (has links)
Le but de cette étude était d'évaluer le rôle des boucles des ganglions de la base et des voies dopaminergiques sur les mécanismes « bottom-up » et « « top-down » du contrôle de l'attention visuelle (AV). Nous avons comparé les performances sur 3 tâches informatisés, appropriées à l'étude de la capture attentionnelle (CA), des mécanismes de sélection de la réponse motrice et d'initiation du mouvement, de deux groupes de patients avec maladie de Parkinson (MP) - un groupe étant évalué dans trois différentes conditions de stimulation électrique (sans stimulation, ou stimulation sélective de la partie sensorimotrice, SM, ou de la partie associative, AS, du noyau subthalamique, NST), l'autre groupe étant évalué dans deux différentes conditions de traitement médical (avec ou sans levodopa) - avec celles d'un groupe des sujets contrôles. Nos résultats suggèrent dans la MP un affaiblissement des mécanismes « top-down » de contrôle de l'AV, ce qui pourrait aussi expliquer indirectement l'augmentation de la CA. Le traitement dopaminergique est efficace dans le rétablissement des mécanismes « top-down » de l'AV, suggérant une implication des voies dopaminergiques dans ce domaine cognitif. Ces voies semblent aussi jouer un rôle dans les mécanismes « bottom-up » de l'attention, comme l'a suggéré le renforcement de la CA sous traitement dopaminergique. La stimulation du NST a montré un effet similaire à celui obtenu par un traitement dopaminergique, en favour d'une implication directe des boucles des ganglions de la base dans le contrôle de l'AV. Nos résultats ont mis en évidence une spécialisation fonctionnelle de différents sous-territoires du NST en ce qui concerne les mécanismes de « top-down ». La stimulation SM produit des effets marqués sur les processus d'initiation de mouvement et des effets positifs sur les mécanismes endogènes de l'AV, alors que la stimulation de la partie AS semble être plus particulièrement efficace dans l'amélioration des mécanismes de sélection de cible. / We aimed to investigate the possible role of cortico-basal ganglia loops and dopaminergic pathways in the mechanisms of top-down and bottom-up control of visual attention (VA). We compared the performances on 3 computerized tasks, respectively suitable to study attentional capture (AC), motor response selection and movement initiation, of two groups of patients with Parkinson's disease (PD), one evaluated in different sets of electrical stimulation (without stimulation, or selective stimulation of the sensorimotor, SM, or associative, AS, parts of the subthalamic nucleus, STN), the other in different conditions of medication (with or without levodopa), with those of a group of controls. Our results showed that in PD there is a weakening of the mechanisms underlying the top-down control of VA, which also would account indirectly account for the enhancement of AC. Dopaminergic treatment proved to be effective in restoring the top-down mechanisms of VA, suggesting an involvement of dopaminergic pathways in this cognitive domain. These pathways seem to play a role also in the bottom-up mechanisms of attention, as suggested by the enhancement of AC under dopaminergic treatment. The STN-stimulation showed a similar effect to that obtained by dopaminergic treatment, establishing a direct involvement of the basal ganglia loops in VA control. Our results highlighted a functional specialization of different sub-territories of the STN in relation to the top-down mechanisms. SM stimulation produced marked effects on the movement initiation processes and appreciable positive effects on endogenous VA mechanisms, while AS stimulation seems to be especially effective in improving the mechanisms of target selection.
14

Attentional capture by a looming ringtone

Liljenberg, Robin January 2017 (has links)
Ringtones are a common distracting sound in modern workspaces. In an earlierexperiment, ringtones increasing in volume (looming) produced greater attentional capture effectin the context of serial short-term memory, than ringtones with sudden onsets that decreased involume (receding). To determine whether this effect occurred merely because the loudest part ofthe looming ringtone coincided with the most sensitive part of the serial short-term memory task,this study repeated the sound conditions of the first experiment, but altered their timing. In thisstudy, the onset of the ringtones were brought forward in time such that the loudest part of thelooming ringtone now coincided with the part of the serial short-term memory task wherein theonset of the looming ringtone occurred in the first experiment. The looming ringtone againproduced more disruption than the receding ringtone, which failed to disrupt performance relativeto the quiet control condition. The presence of a masking sound eliminated the looming ringtoneeffect, as in the previous study. The results here support previous work demonstrating that thelooming sounds give rise to attentional capture and that this reflects an evolutionary adaptation tounconsciously react to approaching sounds/objects.
15

La distraction par des stimuli associés à une récompense et le contrôle attentionnel dans des tâches de recherche visuelle / Distraction by stimuli associated with reward and attentional control in visual search tasks

Matias, Jérémy 16 July 2019 (has links)
Au quotidien, notre attention sélective nous permet de sélectionner les informations pertinentes au regard de notre tâche et d'ignorer celles qui ne le sont pas, afin de maintenir un comportement cohérent avec nos buts. Néanmoins, dans certaines situations, un stimulus complètement non-pertinent peut capturer notre attention contre notre volonté et, de ce fait, produire un phénomène de distraction. La distraction a initialement été considérée comme essentiellement dépendante de la saillance perceptive des distracteurs. Cependant, de récentes études ont mis en évidence que les stimuli associés à l'obtention d'une récompense (i.e., disposant d'une histoire de récompense) sont également susceptibles de produire des effets de distraction particulièrement robustes et persistants (indépendamment de leur pertinence pour la tâche en cours et de leur saillance perceptive). Parallèlement, tout un autre champ de recherche a été consacré à l’étude du contrôle attentionnel qui peut être mis en place afin de prévenir une distraction par des stimuli visuellement saillants. Cependant, à ce jour, très peu de travaux ont tenté de manipuler la qualité du contrôle attentionnel qui peut être instauré pour éviter la distraction par des stimulus associés à une récompense. L'objectif de notre travail était donc de déterminer si, et si oui, dans quelles conditions, ces distracteurs pouvaient être ignorés efficacement ou, au contraire, pouvaient résister au contrôle attentionnel. Dans sept études, nous avons associé des stimuli visuels initialement neutres à une récompense (monétaire ou sociale) afin d’étudier leur impact sur les performances lorsqu’ils apparaissaient comme distracteurs dans des tâches recherche visuelle. Nous avons manipulé la qualité du contrôle attentionnel en faisant varier les contraintes perceptives (i.e., charge perceptive : Études 1 et 2), cognitives (i.e., charge cognitive : Étude 3) ou sensorielles (i.e., dégradation sensorielle : Études 4-7) imposées par la tâche. Nous avons mis en évidence que l'interférence provoquée par un distracteur associé à une forte récompense monétaire, contrairement à celle provoquée par des distracteurs uniquement saillants, peut résister à l'augmentation de la charge perceptive (Étude 1). L'analyse des potentiels cérébraux évoqués par ces distracteurs (Etude 2) suggère que cet effet puisse résulter d’une capture attentionnelle (N2pc) accrue en charge perceptive faible et d’une suppression attentionnelle (Pd) moins efficace en charge perceptive forte pour ces distracteurs. Contrairement à nos attentes, aucun effet de la récompense n'a été observé dans l’étude manipulant la charge cognitive (Étude 3), nous conduisant à proposer que notre manipulation ait pu drainer les ressources cognitives nécessaires à l'apprentissage de l’association distracteur-récompense. Ensuite, nous avons montré que l'augmentation de la pression temporelle (Étude 4-5), réputée pour favoriser la sélection précoce d'une cible, peut au contraire, dans certaines conditions, entrainer une plus grande difficulté à ignorer les distracteurs. Pour autant, dans ces conditions, le simple fait que des distracteurs récompensés puissent apparaître semble impacter encore plus négativement la sélection d'une cible que la pression temporelle elle-même. Enfin, nos deux dernières études (Études 6-7) ont mobilisé un cadre expérimental plus écologique, impliquant la recherche de cibles dans des photographies de scènes routières prises du point de vue d’un conducteur d’automobile et l’apparition de distracteurs récompensés sur l’écran d’un smartphone présent dans l’habitacle. Nous avons mis en évidence que la dégradation sensorielle de la cible (via une augmentation de l'intensité du brouillard) entraine une distraction plus importante pour des distracteurs associés à une récompense sociale, en particulier pour les personnes présentant un niveau élevé de FoMO (Fear of Missing Out ; peur de manquer une expérience sociale). [...] / In our daily activities, selective attention allow us to select task-relevant information among irrelevant ones, in order to maintain consistent, goal-directed behavior. However, sometimes, a completely irrelevant stimulus can capture our attention against our will and, as a result, produce a distraction phenomenon. Distraction was initially considered to be essentially dependent on the perceptual salience of the distractors. Nevertheless, recent studies have shown that stimuli associated with reward outcome (i.e., with a reward history) are also likely to produce particularly robust and persistent distraction effects (regardless of their relevance to the task at hand and their perceptual salience). Alongside, a large body of works has been devoted to the study of attentional control, which could prevent distraction by perceptually salient distractors. However, to date, very little work has attempted to manipulate the quality of the attentional control that could be implemented to avoid distraction by reward history. The objective of our work was therefore to determine whether, and if so, under what conditions, reward-distractors could be ignored or, on the contrary, could resist attentional control. Seven studies were conducted with neutral visual stimuli associated with (monetary or social) reward outcome, in order to investigate how they could affect task performance when they appeared as distractors in visual search tasks. Attentional control was manipulated by varying the perceptual (i.e., perceptual load: Studies 1 and 2), cognitive (i.e., cognitive load: Study 3) or sensory (i.e., sensory degradation: Studies 4-7) demands imposed by the task. We have shown that high-reward distractor interference resists to perceptual load increase, unlike that caused by only salient distractor (Study 1). Our event-related potentials study (Study 2) suggests that this effect may be due to an enhanced attentional capture (N2pc) under low perceptual load and by a less effective attentional suppression (Pd) under high perceptual load for high-reward distractors. Next, contrary to our expectations, no effect of reward history was observed when manipulating cognitive load (Study 3), leading us to propose that our manipulation could have drained the cognitive resources necessary to learn the distractor-reward association. Then, we have shown that the increase in time pressure (Studies 4-5), known to promote the early selection of relevant targets, could also enhanced the difficulty to ignore distractors under some circumstances. Nevertheless, in these conditions, the mere fact that rewarded distractors may appear seems to increase the difficulty to ignore the distractors, more than the time pressure itself. Finally, our last two studies (Studies 6-7) mobilized a more ecological visual search task, involving pictures of driving situations taken from a driver point-of-view, in which reward distractors were displayed on the screen of a smartphone in the vehicle cabin. The sensory degradation of the target (achieved by increasing the fog density outside the car) has led to greater distraction for distractors paired with a social reward, especially for people with a high level of FoMO (Fear of Missing Out; that is, the pervasive apprehension that others might be having rewarding social experiences from which one is absent). These results are discussed in the light of the literature on distraction by reward history and attentional control, in order to integrate the reward history into these models. Moreover, our observations are discussed under the scope of applied researches that focused on driver distraction, in which our work has a particular resonance.
16

Neurophysiological Mechanisms of Auditory Distractibility in the Healthy, Aging or Damaged Human Brain / Les mécanismes neuropsychologiques de la distractibilité auditive dans le cerveau humain sain, âgé ou lésé

Elshafei, Hesham 22 November 2018 (has links)
Les mécanismes volontaires (V) et involontaires (I) de l’attention reposent sur les réseaux dorsal et ventral, convergeant dans le cortex préfrontal latéral (lPFC). La distractibilité accrue liée au vieillissement ou à une lésion frontale pourrait être due à une altération de l’équilibre entre ces mécanismes V et I, essentiel mais rarement étudié. Notre objectif est de tester, dans la modalité auditive, si (1) les oscillations alpha coordonnent l'activité du réseau dorsal, (2) les oscillations gamma celle du réseau ventral, (3) le couplage oscillatoire dans le lPFC maintient l’équilibre entre les deux réseaux. Ce travail vise également à étudier les corrélats oscillatoires de la distractibilité accrue liée au vieillissement ou à une atteinte frontale. Des données MEEG ont été enregistrées alors que des participants réalisaient le Competitive Attention Test, qui permet d’étudier simultanément les mécanismes V et I de l’attention. Nous avons montré que les oscillations alpha reflètent l’activation des mécanismes facilitateurs et suppresseurs de l’attention V, et la communication au sein du réseau dorsal ; alors que les oscillations gamma indexent l’activation du réseau ventral. De plus, le lPFC serait impliqué dans la communication au sein des deux réseaux, et le PFC médian dans l’équilibre attentionnel V/I. Nous avons également montré que la distractibilité accrue était liée à un déficit d’attention V au cours du vieillissement, et à une altération des processus V et I après lésion frontale. Ce travail de thèse offre donc une meilleure compréhension de la dynamique cérébrale oscillatoire sur laquelle repose l'équilibre attentionnel V/I, et donc la distractibilité / Top-down (TD) and bottom-up (BU) mechanisms of attention are supported by dorsal and ventral networks that mainly overlap in the lateral prefrontal cortex (lPFC). A balance between these mechanisms is essential, yet rarely investigated. Increased distractibility observed during ageing or after frontal damage could result from jeopardizing this balance. It has been proposed that distinct oscillatory frequencies support the activation of these two attention networks. Our main aim was to test, in the auditory modality, whether (1) alpha oscillations would coordinate activity within the dorsal TD network, (2) gamma activity would index the activation of the ventral BU network, (3) the lPFC would support the balance between these networks through oscillatory coupling. We also aimed to investigate the oscillatory correlates of the increased distractibility associated with ageing or frontal damage. MEEG data were recorded while participants performed the Competitive Attention Test, which enables simultaneous investigation of BU and TD attention mechanisms. We showed that alpha oscillations indexed facilitatory and suppressive mechanisms of TD attention, and communication within the dorsal network; while gamma oscillations indexed the ventral network activation. Moreover, the lPFC subtended communication in the two networks; with the TD/BU interaction occurring in the medial PFC. We also showed that ageing-related distractibility was of TD deficit origin. Finally, preliminary results suggest that lPFC damage can impact both TD and BU attention. This thesis provides novel insights into the brain oscillatory dynamics of the TD/BU attentional balance supporting distractibility
17

L-DOPA administration shifts the stability-flexibility balance towards attentional capture by distractors during a visual search task

Riedel, P., Domachowska, I. M., Lee, Y., Neukam, P. T., Tönges, L., Li, S. C., Goschke, T., Smolka, M. N. 21 May 2024 (has links)
Rationale The cognitive control dilemma describes the necessity to balance two antagonistic modes of attention: stability and flexibility. Stability refers to goal-directed thought, feeling, or action and flexibility refers to the complementary ability to adapt to an ever-changing environment. Their balance is thought to be maintained by neurotransmitters such as dopamine, most likely in a U-shaped rather than linear manner. However, in humans, studies on the stability-flexibility balance using a dopaminergic agent and/or measurement of brain dopamine are scarce. Objective The study aimed to investigate the causal involvement of dopamine in the stability-flexibility balance and the nature of this relationship in humans. Methods Distractibility was assessed as the difference in reaction time (RT) between distractor and non-distractor trials in a visual search task. In a randomized, placebo-controlled, double-blind, crossover study, 65 healthy participants performed the task under placebo and a dopamine precursor (L-DOPA). Using 18F-DOPA-PET, dopamine availability in the striatum was examined at baseline to investigate its relationship to the RT distractor effect and to the L-DOPA-induced change of the RT distractor effect. Results There was a pronounced RT distractor effect in the placebo session that increased under L-DOPA. Neither the RT distractor effect in the placebo session nor the magnitude of its L-DOPA-induced increase were related to baseline striatal dopamine. Conclusions L-DOPA administration shifted the stability-flexibility balance towards attentional capture by distractors, suggesting causal involvement of dopamine. This finding is consistent with current theories of prefrontal cortex dopamine function. Current data can neither confirm nor falsify the inverted U-shaped function hypothesis with regard to cognitive control.
18

由上而下因素對情緒刺激之注意力攫取的影響 / The influence of top-down factors on attentional capture of emotional stimuli

鐘弘達, Chung hung Ta Unknown Date (has links)
過去的研究指出,具有威脅訊息的情緒臉孔會比正向情緒臉孔快速地吸引個體的注意力。視覺搜尋研究發現情緒臉孔的突顯程度會引發由下而上的注意力攫取,而由下而上的注意力攫取是否能夠被由上而下的因素所凌駕,一直是一個很重要的論爭,因此,本研究同時呈現兩種情緒臉孔,並以文字線索引發由上而下注意力選擇,以探討由上而下的因素是否能夠凌駕情緒臉孔之注意力攫取,並比較不同情緒臉孔攫取注意力的強度。實驗一探討文字線索是否能夠幫助注意力搜尋目標情緒臉孔。實驗二使用一致效果當作注意力攫取指標,探討當臉孔情緒與作業相關時,由上而下因素是否能夠凌駕干擾情緒臉孔為生氣臉孔或快樂臉孔之注意力攫取,以及比較生氣與快樂臉孔攫取注意力的強度。實驗三延續實驗二的研究,將臉孔情緒改為與作業無關,比較生氣臉孔與快樂臉孔攫取注意力的強度。實驗四與實驗二實驗程序相同,但增加倒立中性臉孔與生氣臉孔或快樂臉孔同時呈現情況,如此在以倒立中性臉孔為目標或干擾臉孔情況,可以比較生氣臉孔與快樂臉孔之由上而下因素注意力選擇與由下而上注意力攫取強度。本研究結果在大部分情況下並未獲得一致效果,顯示由上而下之注意力選擇會影響由下而上之情緒臉孔攫取注意力,使得干擾臉孔未能吸引注意力於其上。然而由下而上注意力攫取仍影響搜尋情緒臉孔的反應時間,結果顯示生氣臉孔與快樂臉孔競爭下,生氣臉孔的突顯程度大於快樂臉孔,說明生氣臉孔較快樂臉孔吸引注意力。 / Previous studies using visual search task showed that the saliency of the emotional faces was sufficient to induce the bottom-up attentional capture. It is a critical debate that whether top-down factors can override bottom-up attentional capture. To address this issue, we presented two emotional faces at the same display while using word cues to induce top-down attentional selection. Experiment 1 investigated the effect of word cues on the target face searching. Using congruency effect as an index of attentional capture, Experiment 2 investigated whether top-down factors could override attentional capture of the emotional distractors when emotion is task-relevant and the degree of attentional capture of angry faces was compared with that of happy faces. In Experiment 3, face emotion was changed to be task-irrelevant rather than task-relevant, and the degree of attentional capture of angry and happy faces was also contrasted. In Experiment 4, the invert neutral face was included additionally as another target or distractor. We can use the invert neutral face as the common basis to dissociate the components of top-down attentional selection and bottom-up attentional capture, and contrast the attention effects between angry and happy faces in these two aspects independently. The results showed that congruency effect could not be found in most conditions. This implies that top-down attentional selection can influence the bottom-up attentional capture of emotional faces. But reaction time for searching target was still found to be influenced by bottom-up process. When an angry face competes with a happy face, the saliency of the angry face is higher than the happy face.

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