1,448 research outputs found

    Through the Eyes of the Beholder: Simulated Eye-movement Experience (“SEE”) Modulates Valence Bias in Response to Emotional Ambiguity

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    Although some facial expressions provide clear information about people’s emotions and intentions (happy, angry), others (surprise) are ambiguous because they can signal both positive (e.g., surprise party) and negative outcomes (e.g., witnessing an accident). Without a clarifying context, surprise is interpreted as positive by some and negative by others, and this valence bias is stable across time. When compared to fearful expressions, which are consistently rated as negative, surprise and fear share similar morphological features (e.g., widened eyes) primarily in the upper part of the face. Recently, we demonstrated that the valence bias was associated with a specific pattern of eye movements (positive bias associated with faster fixation to the lower part of the face). In this follow-up, we identified two participants from our previous study who had the most positive and most negative valence bias. We used their eye movements to create a moving window such that new participants view faces through the eyes of one our previous participants (subjects saw only the areas of the face that were directly fixated by the original participants in the exact order they were fixated; i.e., Simulated Eye-movement Experience). The input provided by these windows modulated the valence ratings of surprise, but not fear faces. These findings suggest there are meaningful individual differences in how people process faces, and that these differences impact our emotional perceptions. Furthermore, this study is unique in its approach to examining individual differences in emotion by adapting a methodology previously used primarily in the vision/attention domain

    Notes on Iowa Diatoms XII: Common Diatoms of Big Spirit Lake

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    A natural history of the diatoms of Spirit Lake was in preparation by the senior author prior to his death in 1973. This report is derived from his notes plus some additional observations, and is published in his behalf. A table lists 139 common taxa distributed among 34 genera and notes whether these taxa occur also in Lake West Okoboji and Clear Lake

    Shift and deviate: Saccades reveal that shifts of covert attention evoked by trained spatial stimuli are obligatory

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    The premotor theory of attention predicts that motor movements, including manual movements and eye movements, are preceded by an obligatory shift of attention to the location of the planned response. We investigated whether the shifts of attention evoked by trained spatial cues (e.g., Dodd & Wilson, 2009) are obligatory by using an extreme prediction of the premotor theory: If individuals are trained to associate a color cue with a manual movement to the left or right, the shift of attention evoked by the color cue should also influence eye movements in an unrelated task. Participants were trained to associate an irrelevant color cue with left/right space via a training session in which directional responses were made. Experiment 1 showed that, posttraining, vertical saccades deviated in the direction of the trained response, despite the fact that the color cue was irrelevant. Experiment 2 showed that latencies of horizontal saccades were shorter when an eye movement had to be made in the direction of the trained response. These results demonstrate that the shifts of attention evoked by trained stimuli are obligatory, in addition to providing support for the premotor theory and for a connection between the attentional, motor, and oculomotor systems

    Shift and deviate: Saccades reveal that shifts of covert attention evoked by trained spatial stimuli are obligatory

    Get PDF
    The premotor theory of attention predicts that motor movements, including manual movements and eye movements, are preceded by an obligatory shift of attention to the location of the planned response. We investigated whether the shifts of attention evoked by trained spatial cues (e.g., Dodd & Wilson, 2009) are obligatory by using an extreme prediction of the premotor theory: If individuals are trained to associate a color cue with a manual movement to the left or right, the shift of attention evoked by the color cue should also influence eye movements in an unrelated task. Participants were trained to associate an irrelevant color cue with left/right space via a training session in which directional responses were made. Experiment 1 showed that, posttraining, vertical saccades deviated in the direction of the trained response, despite the fact that the color cue was irrelevant. Experiment 2 showed that latencies of horizontal saccades were shorter when an eye movement had to be made in the direction of the trained response. These results demonstrate that the shifts of attention evoked by trained stimuli are obligatory, in addition to providing support for the premotor theory and for a connection between the attentional, motor, and oculomotor systems

    Modelling mitochondrial site polymorphisms to infer the number of segregating units and mutation rate

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    We present a mathematical model of mitochondrial inheritance evolving under neutral evolution to interpret the heteroplasmies observed at some sites. A comparison of the levels of heteroplasmies transmitted from mother to her offspring allows us to estimate the number Nx of inherited mitochondrial genomes (segregating units). The model demonstrates the necessity of accounting for both the multiplicity of an unknown number Nx, and the threshold θ, below which heteroplasmy cannot be detected reliably, in order to estimate the mitochondrial mutation rate μm in the maternal line of descent. Our model is applicable to pedigree studies of any eukaryotic species where site heteroplasmies are observed in regions of the mitochondria, provided neutrality can be assumed. The model is illustrated with an analysis of site heteroplasmies in the first hypervariable region of mitochondrial sequence data sampled from Adélie penguin families, providing an estimate Nx and μm. This estimate of μm was found to be consistent with earlier estimates from ancient DNA analysis

    Object-based warping in three-dimensional environments

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    Object-based warping is a powerful visual illusion wherein space between features within figural regions is regularly overestimated compared with those within ground regions. Originally, the effect was only examined in displays of two-dimensional (2D) stimuli. The present study sought to examine whether object-based warping persists in more naturalistic viewing conditions, where additional contextual cues are present. Stimuli were presented with either three-dimensional (3D) printed objects (Experiment 1) or 3D objects in virtual reality (Experiments 2–4). The testing metric was actual distance of features (dots) compared with estimated distances made by participants. Responses for the 3D printed stimuli were measured with replica dots on a slide ruler device. The virtual reality experiments collected responses either with a computer mouse or motion-tracked controller and included manipulations of object type, spatial separation, viewing distance of stimuli, and head motion. A standard warping effect in 3D was observed in all experiments, although the effect was not present in one condition that elicits warping in 2D (Occluded Rectangle). The final experiment resolves this discrepancy by reducing the multicomponent object (Occluded Rectangle) to a single component figure, while demonstrating the influence of depth cues on the warping effect under occlusion. Collectively, these experiments reveal that object-based warping is a powerful effect, even in naturalistic settings

    Convolutional neural networks can decode eye movement data: A black box approach to predicting task from eye movements

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    Previous attempts to classify task from eye movement data have relied on model architectures designed to emulate theoretically defined cognitive processes and/or data that have been processed into aggregate (e.g., fixations, saccades) or statistical (e.g., fixation density) features. Black box convolutional neural networks (CNNs) are capable of identifying relevant features in raw and minimally processed data and images, but difficulty interpreting these model architectures has contributed to challenges in generalizing lab-trained CNNs to applied contexts. In the current study, a CNN classifier was used to classify task from two eye movement datasets (Exploratory and Confirmatory) in which participants searched, memorized, or rated indoor and outdoor scene images. The Exploratory dataset was used to tune the hyperparameters of the model, and the resulting model architecture was retrained, validated, and tested on the Confirmatory dataset. The data were formatted into timelines (i.e., x-coordinate, y-coordinate, pupil size) and minimally processed images. To further understand the informational value of each component of the eye movement data, the timeline and image datasets were broken down into subsets with one or more components systematically removed. Classification of the timeline data consistently outperformed the image data. The Memorize condition was most often confused with Search and Rate. Pupil size was the least uniquely informative component when compared with the x- and y-coordinates. The general pattern of results for the Exploratory dataset was replicated in the Confirmatory dataset. Overall, the present study provides a practical and reliable black box solution to classifying task from eye movement data

    Obama cares about visuo-spatial attention: Perception of political figures moves attention and determines gaze direction

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    Processing an abstract concept such as political ideology by itself is difficult but becomes easier when a background situation contextualizes it. Political ideology within American politics, for example, is commonly processed using space metaphorically, i.e., the political “left” and “right” (referring to Democrat and Republican views, respectively), presumably to provide a common metric to which abstract features of ideology can be grounded and understood. Commonplace use of space as metaphor raises the question of whether an inherently non-spatial stimulus (e.g., picture of the political “left” leader, Barack Obama) can trigger a spatially-specific response (e.g., attentional bias toward “left” regions of the visual field). Accordingly, pictures of well-known Democrats and Republicans were presented as central cues in peripheral target detection (Experiment 1) and saccadic free-choice (Experiment 2) tasks to determine whether perception of stimuli lacking a direct association with physical space nonetheless induce attentional and oculomotor biases in the direction compatible with the ideological category of the cue (i.e., Democrat/left and Republican/right). In Experiment 1, target detection following presentation of a Democrat (Republican) was facilitated for targets appearing to the left (right). In Experiment 2, participants were more likely to look left (right) following presentation of a Democrat (Republican). Thus, activating an internal representation of political ideology induced a shift of attention and biased choice of gaze direction in a spatially-specific manner. These findings demonstrate that the link between conceptual processing and spatial attention can be totally arbitrary, with no reference to physical or symbolic spatial information

    Examining the influence of task set on eye movements and fixations

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    The purpose of the present study was to examine the influence of task set on the spatial and temporal characteristics of eye movements during scene perception. In previous work, when strong control was exerted over the viewing task via specification of a target object (as in visual search), task set biased spatial, rather than temporal, parameters of eye movements. Here, we find that more participant-directed tasks (in which the task establishes general goals of viewing rather than specific objects to fixate) affect not only spatial (e.g., saccade amplitude) but also temporal parameters (e.g., fixation duration). Further, task set influenced the rate of change in fixation duration over the course of viewing but not saccade amplitude, suggesting independent mechanisms for control of these parameters

    The political left rolls with the good and the political right confronts the bad: connecting physiology and cognition to preferences

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    We report evidence that individual-level variation in people’s physiological and attentional responses to aversive and appetitive stimuli are correlated with broad political orientations. Specifically, we find that greater orientation to aversive stimuli tends to be associated with right-of-centre and greater orientation to appetitive (pleasing) stimuli with left-of-centre political inclinations. These findings are consistent with recent evidence that political views are connected to physiological predispositions but are unique in incorporating findings on variation in directed attention that make it possible to understand additional aspects of the link between the physiological and the political
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