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Pop-Out Doesn’t Always Poop-Out Bill Prinzmetal and Nadia Taylor University of California, Berkeley Folk psychology suggests that when viewing a scene, a unique item will stand out and draw attention to itself. However, this belief stands in contrast to numerous studies in the attention literature that indicate that a unique item does not stand out in visual search when uniqueness is unrelated to the search task. For example, in searching for a target letter in an array of colored letters, subjects are no faster when the target is a unique color than when it is not, if uniqueness is unrelated to being the target. This finding holds of properties including color, shape, and motion. In visual search, unique popout poops out. We hypothesized that this nonintuitive finding is the results of task demands of visual search, and that when the task does not involve visual search, uniqueness will popout. We tested this hypothesis in a task in which subjects were presented an array of letters and ask to respond aloud, as quickly as possible, the identity of any one of the letters. Subjects were significantly more likely to respond with a uniquely colored letter than would be expected by chance. Thus, in a task in which subjects blurt out the first thing that they see, unique popout does not poop out. These results are discussed both in terms of theories of visual attention and in applied research in web page design. (2) Encoding during the attentional lapse Jonathan Smallwood and Jonathan Schooler University of British Columbia This talk will review a series of recent studies, which investigate the ability of an individual to encode information during periods when their attention has departed from task relevant information. In these studies attentional lapses can be defined in behavioral terms, when the participants fails to inhibit a response on a no go task (Robertson et al., 1997) or via self-report, when the participant verbally or otherwise indicates that their attention is off task (Smallwood et al., 2003). Convergent evidence from these two lines of evidence suggests that periods in which attention is off task are associated with a shift in retrieval towards retrieval based on familiarity rather than recollection. The implications of these findings are discussed in the context of recent accounts of awareness. Is cognitive control managed by a single central mechanism or by multiple independent systems? (3) Is cognitive control managed by a single central mechanism or by multiple independent systems Mary Beth Knight & Diego Fernandez-Duque Villanova University The title question was addressed by a paradigm in which color and number Stroop tasks alternated every trial. In Experiment 1, dynamic trial-to-trial changes of cognitive control were assessed: incongruent trials led to task-specific reduction of conflict (trial n+2), but no cross-task modulation (trial n+1). In Experiment 2, the ratio of incongruent trials in the color Stroop trials varied between blocks, while the ratio in the alternating number Stroop task remained constant. The increase in incongruent trials led to a task-specific modulation of conflict resolution in color Stroop, but the effect did not generalize across tasks. In sum, the results from both studies argue against a single central mechanism of cognitive control. Experiment 3 (in progress) investigates whether a voluntary mindset to process conflict in one task enhances conflict resolution in other tasks. Results will be discussed in relation to neurobiological theories of cognitive control. (4) Integration of auditory and visual long-range sequences: Case study of a clarinet concerto Authors: Bradley Vines (1), Carol Krumhansl (2), Marcelo Wanderley (3), Daniel Levitin (1,3)* (1) Department of Psychology and Program in Behavioral Neuroscience, McGill University (2) Department of Psychology, Cornell University (3) Department of Music Theory, McGill University The literature in psychology is rich with studies of audio/visual integration over short-term stimuli, such as is the case with the McGurk Effect, the Greenwich Observatory Problem (ie "The Perceptual Moment" work of the 1800s), and the Ventriloquism Effect. Relatively fewer studies have looked at the integration over long-term sequences such as musical pieces. We studied performances of a Stravinsky clarinet concerto as experimental participants made real-time continuous judgements of musical emotion and musical structure. Using functional data analysis techniques we were able to quantify the relative importance of the auditory vs. the visual channel in contributing to participant's perception of structure and emotion, and the degree of audio/visual integration present at different parts of the piece. The visual channel in music performance indeed conveys information that is sometimes orthogonal to, and sometimes complements, the auditory information. We also were able to quantify the ways that audio/visual integration changed over the course of the musical piece. (5) Quick Minds Don't Blink: Electrophysiological Correlates of Individual Differences in Attentional Selection. Sander Martens, Neuroimaging Center, University of Groningen, the Netherlands Jaap Munneke, Experimental Psychology, University of Groningen, the Netherlands Dick Smid, Psychiatry Department, University of Groningen, the Netherlands Addie Johnson, Experimental Psychology, University of Groningen, the Netherlands A well-established phenomenon in the study of attention is the attentional blink: A deficit in reporting the second of two targets when it occurs 200-500 ms after the first. Although the effect has been shown to be robust in a wide variety of task conditions, not every individual participant shows the effect. We measured EEG activity for "non-blinkers" and "blinkers" during execution of a task in which two letters had to be detected in an RSVP stream of digit distractors. Non-blinkers showed an earlier P3 peak, suggesting that they are quicker to consolidate information than are blinkers. Differences in frontal selection positivity (FSP) were also found, such that non-blinkers showed a larger difference between target and non-target activation than blinkers did. Non-blinkers seem to extract target information at an earlier stage than blinkers do, allowing them to reject distractors more easily and leaving sufficient resources available to report both targets. (6) Nelson Cowan (1), Emily M. Elliott (2), J. Scott Saults (1), and Candice C. Morey (1) (1) Department of Psychological Sciences, University of Missouri, Columbia (2) Department of Psychological Sciences, Louisiana State University Working memory is the limited amount of information that can be retained temporarily in a state that is more quickly and reliably accessible than the rest of the memory system. Yet, there has been little consensus on how working-memory capacity should be measured. George Miller (1956) noted that adult humans can recall about 7 items in the correct serial order but his reference to that "magical" number was tongue-in-cheek. We will sketch out conditions in which one critically important component of working-memory capacity, the contents of the focus of attention, might be measured. The conditions are those in which stimulus items are familiar, task demands prevent or control the grouping of stimulus items into higher-level units, and covert rehearsal is prevented or is impractical. Under a wide variety of such circumstances, it can be shown that adults recall about 4 chunks of information. Whereas many researchers believe that working-memory performance estimates how well attention maintains a goal in the presence of interference, we present research suggesting that working memory involves an adjustable attentional focus that can zoom in to maintain a goal or zoom out to apprehend up to about 4 concurrent chunks. Its capacity, like goal maintenance, predicts intellectual aptitude. (7) Clark G. Ohnesorge, Nick Palmer, Justin Kalemkiarian, Gustavus Adolphus College We present data from several studies investigating hemispheric specialization for self-recognition. Researchers have recently addressed this issue using techniques ranging from behavioral responding to neuroimaging during self-recognition, often using stimuli created by morphing together each subjects' face with that of a familiar other. Generally split-visualfield presentation is used to support inferences about lateralization. While previous studies have shown changes in response probability (i.e. the classification of a particular stimulus as either "self or "other) as a function either of visual field or response hand , it has remained unclear whether those changes are due to differences in perceptual sensitivity or decisional bias. In our first study we presented individualized morphed stimuli using a split-visualfield technique and using a detection design (theory of Signal Detectability) to reveal large effects in both Sensitivity and in Bias. In each case the effect was an interaction between Visual Field and Response Hand. In a second study we used a 2afc task to eliminate bias and yield a cleaner, but somewhat different view, of the Sensitivity effect we observed in our first study. We are currently extending our studies to evaluate the generality of our findings for a broader range of perceptual discrimination tasks. (8) Content Borrowing and Vivid False Memories James Michael Lampinen, Christopher Meier, , Jack Arnal, Juliana Leding, University of Arkansas False memories are sometimes accompanied by surprisingly vivid experiential detail that makes them difficult to distinguish from actual memories. The authors have proposed that such strikingly real false memories are produced by a process called content borrowing. In content borrowing details from presented items are errantly borrowed to corroborate the occurrence of the false memory item. In two experiments using think out loud protocols at both study and test, evidence for content borrowing occurred for more than half of the false remember judgments participants reported. (9) David G. Elmes, Washington and Lee University Miller and Lachman’s (1999) socio-cognitive theory of memory provided the impetus for a series of studies concerned with factors associated with memory performance and attitudes about memory performance of college-aged and elderly participants. The general procedure involved assessments of the participants‚ beliefs about their own memory ability. They then judged the causes of memory problems exhibited by both young and elderly targets in written scenarios. Negative attitudes, such as ageism, are associated with fatalistic views of the memory failures of targets. Elderly subjects who received positive, but false feedback about their memory performance performed better than elderly controls on a continuation of the task and had more negative attitudes about targets‚ memory failures, especially the elderly targets. False feedback had a minor influence on college students. The elderly are generally more fatalistic and dispositional in their attitudes about memory than are college students. (10) Evidence for Path Integration by Humans Edward H. Cornell and Elaine Greidanus, Department of Psychology, University of Alberta There are two accounts of navigation processes that track direction and speed of movement, path integration and dead reckoning. Path integration involves the continuous sensing of linear and rotary velocity and acceleration. Automatic calculations produce a moment-to-moment updating of self to an anchor point for travel. In contrast, dead reckoning can be accomplished using episodic memories. Legs and turns are configurally represented as routes and the bearing to the origin of travel can be estimated by connecting the endpoint of the current leg to the starting point of the first leg. Because people take more time to estimate the origin of routes with more legs and turns, it is argued that we use a process akin to dead reckoning. In the research reported here, we find that people show better than chance performance in estimating the origin of outdoor routes when they are asked to point immediately. It appears that we have available a continuously updated representation of our position and heading based on the cues that accompany self-movement. (11) Circles of working memory: Exploring the capacity of the focus of attention and the retrieval dynamics of focus-switching Chandramallika Basak & Paul Verhaeghen Department of Psychology and Center of Health and Behavior, Syracuse University In three experiments, we explore the process of switching items in and out of the focus of attention within working memory. The task used is an N-Count task (expanded from Garavan, 1998). This task yielded a focus size of one. Additionally, we found that focus switch costs in RT increased with working memory load, but only in untrained subjects, and that maintaining and switching to and from a passive load did not increase costs or decrease the accuracy of items. The results support a concentric theory of working memory: a small focus at its core, a surrounding area of (at least) 3 readily available items, and a still wider region of passive storage, possibly more LTM than WM. Retrieval dynamics can take the form of either a controlled search or of immediate content-addressable retrieval, depending on the task and the amount of prior practice. (12) Long Term Activation of Lexical and Sublexical Representations Meghan Sumner and Arthur Samuel (presented by Arthur Samuel) Dept of Psychology SUNY Stony Brook When a listener hears a word like “tape”, current theories of spoken word recognition assert that recognition involves the activation of both lexical (“tape”) and sublexical (e.g., /t/, /e/, /p/) representations. In contrast, when an unfamiliar utterance (“dape”) is heard, no lexical representations can be settled on. Using a long-term priming paradigm, we examine whether representations remain active for at least 10-20 minutes. We approach this by examining lexical decision times for nonwords (e.g. “dape”), as a function of the words or nonwords heard 10-20 minutes earlier. In four experiments we find that the time needed to identify a nonword as a nonword is delayed if a similar word was heard 10-20 minutes before; there is no such delay if the nonword itself had previously been heard. The delay suggests that the word’s lexical representation remains active, and competes with the nonword during its recognition. This interference is found both for items sharing onsets (“flute-floose”) and offsets (“tape-dape”). The equivalence of these two cases supports word recognition models in which a word’s lexical neighborhood determines the set of lexical competitors. (13) The effects of stimulus complexity on switching the focus of attention in visual working memory Yanmin Zhang and Paul Verhaeghen, Syracuse University We explored the effects of stimulus complexity on focus switching costs in visual working memory. The task was an identity-judgment N-Back task; the stimuli were abstract shapes formed by squares in a virtual 3x3 grid. Stimulus complexity was manipulated by varying the number of squares. In Experiment 1, complexity did not matter for N=1, but it did for N=2, indicating that the focus switch is executed more slowly and less accurately for more complex stimuli, even though the comparison process occurs equally fast and accurate for all levels of complexity. The effect appears to be larger for new than for old stimuli, suggesting that the focus switching effect is at least partially due to encoding difficulties. In Experiment 2, we find that further increasing the load to N=3 does not qualitatively alter the effects, demonstrating that the focus switch is the locus of the effect, and not working memory load. (14) Contingent Attentional capture: Timecourse, semantics, and electrophysiology Pierre Jolicoeur, Emilie Leblanc, David Prime, Paola Sessa, Roberto Dell'Acqua, and Nicolas Robitaill, Université de Montréal When searching for a particular type of target based on a particular cue (e.g., red when looking for a red digit among digits of other colours), distractors that match the target search cue (e.g. red) appear to attract attention to their spatial location whereas equally salient distractors (e.g., green) do not. We studied this contingent attentional capture phenomenon in the attentional blink phenomenon, and also using variants of the paradigm developed by Folk, Leber, and Egeth (2002, Perception & Psychophysics). We studied its timecourse, extended it to non physical features (e.g., letters vs. digits), and examined electrophysiological correlates using the N2pc event-related potential. We also examined a similar phenomenon in a paradigm involving attentional control settings, meaning, and spatial capture described by Pratt and Hommel (2003, JEP:HPP). Psychophysical and electrophysiological results confirm and extend the contingent capture model developed by Folk and his colleagues. (15) Sheri Mizumori, Oxana Yeshenko and David M. Smith, University of Washington Neuropsychological data and animal research suggest that hippocampus plays a critical role in episodic-like learning and memory. Neurophysiological evidence, however, indicate that hippocampal neurons fire in relation to an animal’s position in space. This finding suggests that hippocampus contributes to adaptive navigation. Recent studies have attempted to bridge these disparate theories of hippocampal function. Emphasis has been placed on the role that hippocampal ‘place cells’ might play in the evaluation of the spatial context in which learned behaviors occur. These efforts have revealed that place cells code not only sensory and motor information, but also information about an animal’s internal state, task goals, reinforcement history, and the cognitive strategy used to solve a task. Moreover, hippocampus may organize such spatial context information across time. Thus, hippocampal place cells may be uniquely qualified to make significant contributions to episodic learning and memory by temporally distinguishing meaningful events, or spatial contexts. (16) Comparative Studies of Spatial Encoding Strategies. Marcia Spetch, University of Alberta When trained to find a goal that bears a constant spatial relationship to an array of identical discrete landmarks, adult humans consistently adopt a relative encoding strategy (e.g., learning a rule such as “in the middle”). This strategy is revealed through array expansion tests in which the landmarks are moved farther apart. On these tests, adult humans adjust their distance of searching from individual landmarks and maintain the same relative location to the array as a whole. By contrast, birds, rodents and non-human primates adopt an absolute encoding strategy: On expansion tests they maintain the same distance from individual landmarks as in training. These contrasting behaviors hold across both computer-based and open field tasks, and they appear to reflect strategy rather than ability differences. For example, birds can use a relative rule if trained on a task that cannot be solved with absolute encoding, and they are more likely to use a relative encoding strategy if the spatial information is derived from walls of an enclosure rather than discrete landmarks. Recent studies using three different tasks with human children (ages 3-9) have revealed that children also differ from adults in their preferred strategy. Although children and non-humans may be capable of using relative spatial information, a preference for using relative encoding of spatial information from landmark arrays may be unique to adult humans. We speculate that experience with symbolic and scale transformation tasks, such as map reading, may contribute to this preference. (17) Neural mechanisms involved in the positive and negative effects of glucose on spatial working memory Marise Parent, Georgia State University Modest increases in circulating blood glucose levels enhance memory, whereas larger elevations produce deficits. Several lines of evidence suggest that these mnemonic effects of glucose are mediated, at least in part, via an effect on the brain. For instance, direct infusions of glucose into specific brain regions, such as the septum or hippocampus, influence spontaneous alternation, a measure of spatial working memory. The findings of these studies have led to the hypothesis that glucose interacts with different neurotransmitter systems in the septo-hippocampal system to enhance or impair spatial working memory. Specifically, the gamma-aminobutyric (GABA) neurotransmitter system in the septum may contribute to the impairing effects of glucose, whereas increases in hippocampal acetylcholine function likely contribute to its enhancing effects. Combined, the evidence indicates that the effects of glucose on spatial working memory are not mediated via global, non-specific mechanisms, but rather involve interactions with particular neurotransmitters in specific brain regions. (18) The evolution of spatial orientation and hippocampal function Lucia Jacobs, University of California, Berkeley The mammalian hippocampus mediates diverse cognitive processes, from human episodic memory to spatial memory in birds and mammals. The relationship between these and other forms of memory in mammals and other vertebrates is still unfolding. As with other examples of complex cognitive traits, the current functions of the hippocampus may be best understood in light of its evolutionary history. Its function must therefore be understood not only across forms of memory or across mammalian species, but also comparisons of function across other medial pallium homologues, such as the lateral telencephalic pallium of teleost fishes, the medial pallium of amphibians and the medial cortex of reptiles. In the parallel map theory of hippocampal function the cognitive map emerges from the integration of two components, the bearing and the sketch map. According to the theory, these two maps are mediated by dissociable hippocampal subfields, the bearing map by the dentate gyrus and the CA3 subfield of Ammon’s horn, and the sketch map by the CA1 subfield. Because these hippocampal subfields differ in their evolutionary history and degree of development among different vertebrate taxa, an analysis of the structure of the medial pallium homologue should predict spatial strategy under similar experimental conditions. Evidence from other vertebrate groups may therefore help explain recent results on the dissociable functions of the subfields of Ammon’s horn. (19) Relations between visual attention and working memory Philip Quinlan, Univ. of York, Yorkshire There is increasing interest in the relationship between the operation of short-term (working) memory and visual attention. A basic approach is to examine how performance on an attentional task may be affected by the demands of a second and concurrent memory task. Relevant work has used this approach to examine particular issues concerning processes of visual feature binding. In other cases variants on the paradigm have been used to garner support for a more general framework for thinking about attentional mechanisms. The present paper will introduce both strands of research. Experiments will be presented that examine the idea that filling up working memory increases the likelihood of interference from irrelevant sources in the attentional task. Discussion will focus on Treisman's feature integration theory and Lavie's load theory. (20) In behavioral and fMRI analyses, we investigated inhibitory control processes at both stimulus input and response decision. Conflict during stimulus encoding was manipulated by having subjects respond to the direction indicated by arrows in the presence of Stroop-like interference (e.g., direction of arrow conflicting with location of arrow). Conflict during response decision was manipulated by having subjects respond to the direction opposite to that indicated by the arrow on half of the trials. These „anti-response‰ trials were intermixed with „pro-response‰ trials and cued by the color of the arrow. Thus, both Stroop-like interference (congruent vs incongruent conditions) and anti-response interference (anti- vs pro- responses) were manipulated within the same block of trials. Reaction time data suggest that these two effects are additive. Neuroimaging data suggest both similar and different dorsolateral prefrontal regions are recruited for inhibitory control of stimulus features compared to the control of response selection. These findings are couched in terms of dynamic filtering theory, which identifies different executive components for selection and rerouting. (21) On the time course of consolidation of a complex, implicitly learned task Arthur S. Reber & Leib Litman, Brooklyn College and the Graduate Center of CUNY The sequential reaction time (SRT) task has two distinct components to it, a cognitive component where knowledge about the sequence of events is acquired and a sensorimotor component where procedural knowledge about pressing appropriate buttons to lights is learned. By manipulating two classic methods for evaluating how long it takes for these skills to undergo long-term potentiation, we found two distinct time courses for consolidation. The motoric component consolidates monotonically and is essentially completely established in about five hours. The cognitive component requires a night's sleep and is not fully robustly represented until approximately 24 hours has passed. The data are discussed in the context of neural mechanisms of consolidation and the need to distinguish the various kinds of learning in this, seemingly simple, task. Progress monitoring versus representational change accounts of two insight problems. Ed Chronicle, Yun Chu and Andy Dewald, University of Hawaii at Manoa There has been a considerable resurgence of interest in the topic of insight in recent years. Two broad theoretical positions have been established. The first, progress-monitoring theory, suggests that problem solvers monitor their progress against a plausible criterion based on the problem statement, and that they maximize the value of moves made early in their attempt. Impasse occurs when maximizing moves that meet the criterion of progress - but are incorrect - are selected and retained. The second, representational change theory, suggests that the mental representation of problem components must change, for example by dechunking - before an impasse can be overcome. In this paper we present data from a series of experiments with two insight problems - the ball weighing problem and the cheap necklace problem - that allow direct comparison of the two theoretical accounts. Hints that facilitated the necessary representational change - dechunking for the cheap necklace problem and grouping for the ball weighing problem - were less effective in promoting solution than simple verbal hints not to maximize on the first move. We discuss these data in terms of an information-processing account of insight. (23) Automatic Attention and Accuracy: An Alliterative Account Ed Awh and Sei-Hwan Oh, University of Oregon Affiliation: University of Oregon Prinzmetal, McCool and Park (2005) examined the effects of voluntary and involuntary attention and suggested that involuntary attention influences which locations are consulted to drive responses, but not the quality of the perceptual representations that are derived from the cued locations. This hypothesis predicts reaction time but not accuracy effects under conditions where stimulus-driven shifts of attention are elicited using non-informative spatial cues. Prinzmetal et al. verified this conclusion using four different cueing paradigms and a variety of visual targets. In these studies, however, the target displays contained little interference from irrelevant objects. Given that one of the primary functions of attention is to resolve interference between relevant and irrelevant objects, greater sensitivity to accuracy effects might be achieved using high-interference displays. Using distractor-free displays, we replicated the findings of Prinzmetal et al. -- non-informative spatial cues did not affect the accuracy of target discrimination. However, when the same targets were embedded in a distractor-laden display, we found robust improvements in accuracy at the cued locations. We suggest that stimulus-driven visual selection can improve the quality of perceptual representations through a process that resolves interference between relevant and irrelevant visual representations. (24) Neural mechanisms mediating the flexible representations of cognitive and affective associations Christine I. Hooker, Robert .T. Knight, and Mark D‚Esposito
Prior research shows that the medial and orbital prefrontal (PFC) cortices mediate the flexible learning and updating of stimulus reinforcement contingencies. However, the dorsolateral PFC is also involved in learning and updating associations. We investigated whether different systems exist for cognitive versus affective associative learning. In an event-related fMRI study, healthy adult subjects performed three domain specific visual discrimination, reversal-learning tasks: 1) object-emotion association in which a person on the screen has an emotional (happy or fearful) or neutral reaction to a novel object. 2) an object-physiological association (i.e. the person has a physiological but nonemotional response), and 3) an object-object association in which each object is associated with a particular color. After an initial learning period, the association is reversed, and subjects guide subsequent responses by using feedback gained from the trial. Results show a dissociation in the prefrontal cortex whereby the medial PFC is more involved in learning object-emotion associations as compared to object-physiological or object-object associations. However, the dorsolateral PFC is more involved in learning object-object associations than object-emotion or object-physiological association. In addition, we found that neural activity during the object-emotion association task shows individual variability according to reward and punishment sensitivity. When learning from fearful faces, brain activity in the midbrain and thalamus shows a positive correlation with self-reported behavioral sensitivity to punishment, as measured by the behavioral inhibition scale. When learning from happy faces, brain activity in the superior temporal sulcus and ventral prefrontal cortex shows a positive correlation with self-reported reward sensitivity, as measured by the behavioral activation scale. These results illustrate domain specificity and personality influences in association learning. (25) A Binary Mapping Hypothesis for Perception of Visual Structure Hal Pashler & Liqiang Huang, University of California, San Diego Studies of the perception of multidimensional displays have focused almost entirely on search tasks. However, observers often view scenes without trying to find any particular target, and when doing so, they frequently apprehend structures and patterns, not just the presence of "target" elements. Exactly what kinds of structures and patterns can people detect without scrutiny, and what role does attention play? We propose and discuss what we call the binary mapping theory, according to which perception of structure in multidimensional displays is constrained to occur through one or more iterations of a two-stage sequence: (1) voluntary dichotomization of the display by attending to a subregion in a single featural dimension, and (2) the spatial analysis of the envelope(s) characterizing "positive" regions of the display. This hypothesis is related to feature integration theory, but differs in some important ways. Some tests of the theory will be presented, involving perception of figure-ground segregation, color symmetry, and various forms of clustering and higher order structures. The practical implications for visual interpretation of multidimensional data (e.g., in visual data mining and medical imaging) will also be discussed. (26) Do perceptually demanding objects consume more working memory capacity? Edward K. Vogel & Akiko Ikkai, University of Oregon Visual working memory (VWM) is well known to be highly capacity-limited, typically estimated to be approximately 3 simple objects. Here we examined whether this capacity is best expressed in terms of the number of items or the perceptual requirements of the memory items. To do this we examined an ERP correlate of maintenance in VWM while subjects performed a memory task with items that were either perceptually demanding or posed minimal perceptual requirements. The amplitude of the Contralateral delay activity (CDA) has previously been shown to be strongly modulated by the number of items currently held in memory. In this study, we examined whether the amplitude of this activity would be modulated by the perceptual requirements of the memory items, irrespective of the number of items in the display. We manipulated the luminance of the memory items (bright vs. dim) as well as set size (2 items vs. 4 items) in a standard VWM task. Behaviorally, performance was significantly impaired on the perceptually-challenging dim trials as compared to the bright items. However, despite this increase in the perceptual demands for the dim memory items, CDA amplitude was not modulated by the perceptual requirements imposed by the items in the display but was primarily sensitive to the number of items in the display. These results support models that propose that the number of items and not the properties of the items primarily determines the capacity of visual working memory. (27) Top-down and Bottom-up Control in Attention and Saccades: Evidence from Attentional Capture, Oculomotor Capture, and IOR Shu-Chieh Wu and Roger Remington, NASA Ames Research Center The close coupling between attention and saccades is widely observed and well accepted. Because of this accepted coupling, phenomena associated with saccadic eye movements, such as oculomotor capture and inhibition-of-return (IOR), have been used as measures of the orienting of attention. Here we show that despite the acknowledged close coupling, attention and saccades can be dissociated by their differential response to color and onset distractors. In one series of studies we show that irrelevant onset distractors produce oculomotor capture in saccade conditions, even though those same distractors fail to capture attention in fixation conditions. Conversely, color distractors produce attentional capture in fixation conditions, even though those same distractors fail to produce oculomotor capture in saccade conditions. In a separate series of experiments we find IOR to onset distractors at long SOAs even with strong evidence that at short SOAs attention was captured by a color distractor, which was presented simultaneously with the onset. Conversely, we find no IOR to color cues even with strong evidence that attention was drawn to them. We propose that this pattern of results indicates the presence of two separate systems, one associated with saccade control, the other with attention. The system for saccade control is sensitive to transient stimulation and does not in itself reflect top-down goals mediated by attentional control settings. The system for controlling attention is sensitive to a wide range of stimulus properties and involuntarily orients attention based on task relevant properties mediated by attentional control settings. Possible neural systems for these two systems are discussed. (28) Contingent Inhibition of Return Charles L. Folk, Villanova University There is substantial debate concerning the degree to which bottom-up attentional deployment (also referred to as “attentional capture”) can be modulated by top-down expectancies, at least in the case of search for targets defined by discontinuities in simple features (i.e., featural singletons). Some argue that attentional capture by salient featural singletons is impervious to top-down modulation, while others argue that virtually all capture effects are contingent on top-down “attentional control settings”. Evidence for both of these positions will first be reviewed, with particular emphasis on recent evidence for the former position showing that task-irrelevant color singletons produce Inhibition of Return (IOR) in a hybrid cuing/visual search task. A set of studies will then be described showing that IOR in such tasks is eliminated with systematic variations in the properties defining the target and those defining the distracting singletons. It is concluded that the recent IOR data do not, in fact, provide convincing evidence that irrelevant singletons capture attention independent of top-down set. (30) Repeated masks are less effective Trafton Drew & Edward K. Vogel, University of Oregon When a target is immediately followed by an irrelevant stimulus, it is generally harder to accurately report than when it is presented in isolation. The concept of using target masks is pervasive, yet the underlying mechanisms that predict the efficacy of a particular masking stimulus are still not fully understood. For example, what happens when a target mask is repeated? We investigated this question using a simple target detection task. Subjects were asked to pick a target out of a circular array of 7 other non-targets. The target array was preceded and followed by a circular array of random letters. On half of the trials, the distractor arrays were identical before and after the target. On the other half, both masks were novel. We found a benefit of repeated masks. That is, target detection was significantly better when the trial repeated the same mask twice as compared to trials when there were two novel masks. Under certain circumstances, repeated stimuli have been found to be more difficult to perceive (repetition blindness, Kanwisher, 1987) while under others there is a clear benefit for seeing the same thing twice (repetition priming, Henson et al, 2000). It is not yet clear whether the current results are due to participants being primed to the mask or ‘blind’ to it and it is possible that the same mechanisms may actually underlie both of these processes. (31) Neural correlates of voluntary and involuntary attention: dorsal and ventral stream dissociations Michael Esterman1, Joseph DeGutis1, Eliot Hazeltine2, Timothy Verstynen1 & William Prinzmetal1, 1University of California, Berkeley, 2University of Iowa Behavioral evidence suggests differences between voluntary (endogenous) and involuntary (exogenous) spatial attention. Using fMRI, we sought to dissociate the neural correlates of these processes. Subjects performed a face recognition task. We manipulated involuntary attention by preceding the target face with a spatial cue (box brightening) that was uncorrelated with the subsequent target position. For voluntary attention, we used identical spatial cues, but the stimulus appeared in the cued location on 75% of the trials (valid trials) and in the uncued location on 25% of the trials (invalid trials). The stimulus parameters were identical for voluntary and involuntary attention experiments, only the proportion of valid and invalid trails differed. As in previous studies, we found a behavioral dissociation between voluntary and involuntary attention: both affected RT, but only voluntary attention affected accuracy. We found that the fusiform face area (FFA) was modulated by the spatial cue, independent of the presentation of the target face. Furthermore, the FFA was more active when target faces were preceded by predictive cues (voluntary attention) than non-predictive cues (involuntary attention), suggesting that the FFA is more strongly modulated by voluntary attention. In the parietal lobe there was generally greater activity in the invalid than valid trials for both voluntary and involuntary attention, indicating that re-orienting of attention correlated with increased parietal activity. However, within the parietal lobe, there were qualitative differences in the locus of maximum activation for voluntary and involuntary attention indicating that they have partly dissociable neural correlates. Together, these results indicate that automatic and voluntary attention may be controlled by only partially overlapping dorsal brain regions, and that the mechanism of each type of attention may be dissociated in the ventral stream. |
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