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    ABSTRACT: Curvature is a highly informative visual cue for shape perception and object recognition. We introduce a novel illusion-the Lemon Illusion-in which subtle illusory curvature is perceived along contour regions that are devoid of physical curvature. We offer several perceptual demonstrations and observations that lead us to conclude that the Lemon Illusion is an instance of a more general illusory curvature phenomenon, one in which the presence of contour curvature discontinuities lead to the erroneous extension of perceived curvature. We propose that this erroneous extension of perceived curvature results from the interaction of neural mechanisms that operate on spatially local contour curvature signals with higher-tier mechanisms that serve to establish more global representations of object shape. Our observations suggest that the Lemon Illusion stems from discontinuous curvature transitions between rectilinear and curved contour segments. However, the presence of curvature discontinuities is not sufficient to produce the Lemon Illusion, and the minimal conditions necessary to elicit this subtle and insidious illusion are difficult to pin down.
    Frontiers in Human Neuroscience 02/2015; 9:95. DOI:10.3389/fnhum.2015.00095
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    ABSTRACT: The Ebbinghaus illusion is a classic example of the influence of a contextual surround on the perceived size of an object. Here, we introduce a novel variant of this illusion called the Dynamic Ebbinghaus illusion in which the size and eccentricity of the surrounding inducers modulates dynamically over time. Under these conditions, the size of the central circle is perceived to change in opposition with the size of the inducers. Interestingly, this illusory effect is relatively weak when participants are fixating a stationary central target, less than half the magnitude of the classic static illusion. However, when the entire stimulus translates in space requiring a smooth pursuit eye movement to track the target, the illusory effect is greatly enhanced, almost twice the magnitude of the classic static illusion. A variety of manipulations including target motion, peripheral viewing, and smooth pursuit eye movements all lead to dramatic illusory effects, with the largest effect nearly four times the strength of the classic static illusion. We interpret these results in light of the fact that motion-related manipulations lead to uncertainty in the image size representation of the target, specifically due to added noise at the level of the retinal input. We propose that the neural circuits integrating visual cues for size perception, such as retinal image size, perceived distance, and various contextual factors, weight each cue according to the level of noise or uncertainty in their neural representation. Thus, more weight is given to the influence of contextual information in deriving perceived size in the presence of stimulus and eye motion. Biologically plausible models of size perception should be able to account for the reweighting of different visual cues under varying levels of certainty.
    Frontiers in Human Neuroscience 02/2015; 9:77. DOI:10.3389/fnhum.2015.00077
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    ABSTRACT: Despite implications for theory and treatment, commonality in responding to non-bereavement and bereavement losses are not well explicated. This study identified the factor structure of the three most common responses to bereavement, prolonged grief, posttraumatic stress, and major depression in a bereaved community sample (n=151, 59% female, 68% white) from the U.S. recruited from Amazon's MTurk using a cross-sectional survey design, then cross-validated the structure in samples where people had lost other potentially self-defining roles; one's employment (n=157, 47% female, 69% white) and one's marriage (n=116, 62% female, 80% white). Results indicated that symptoms of prolonged grief, posttraumatic stress, and major depression were distinct factors in the bereaved sample, the three-factor solution was a good fit for the job-loss and divorce samples, and levels of grief in each sample appeared to be best predicted by time since loss and centrality of the loss to one's identity. Limitations include potential sample bias due to convenience sampling, and the cross-sectional design did not allow examination of the stability of factors over time. These results suggest that grief is not a unique response to loss of loved one but instead may be a common phenomenology across types of loss. This implies that facilitating meaningful engagement in self-defining activities that compensate for the disrupting loss might be efficacious in promoting grief resolution without the need for working through individuals' emotional attachment to a specific individual or processing one's emotional responses to the loss.
    Journal of Affective Disorders 06/2014; 161:136-43. DOI:10.1016/j.jad.2014.03.018
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    ABSTRACT: Alexithymia is a term used to describe individuals who seem unable to experience or at least describe emotions. This paper offers a theoretical interpretation of alexithymia from a radical behaviorist perspective. While there have been attempts to explain the etiology of alexithymia, the current analysis is unique in that it provides direct treatment implications. The pragmatic analysis described focuses on the verbal behavior of individuals rather than looking “inside” for explanations. This is supported by a review of experimental research that has failed to find consistencies among alexithymic individuals’ physiological responding. Descriptions of the various discriminative and consequential stimulus conditions involved in the complex learning histories of individuals that could result in an alexithymic presentation are provided. This analysis helps situate the alexithymia construct in a broader behavior analytic understanding of emotions. Finally this paper outlines implications for assessment and treatment, which involve influencing discriminative and consequential interpersonal stimulus conditions to shape verbal behavior about emotions.
    04/2014; DOI:10.1016/j.jcbs.2014.03.002
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    ABSTRACT: A recent study showed that color synesthetes have increased color sensitivity but impaired motion perception. This is exciting because little research has examined how synesthesia affects basic perceptual processes outside the context of synesthetic experiences. The results suggest that synesthesia broadly impacts perception with greater neural implications than previously considered.
    Trends in Cognitive Sciences 02/2014; 18(5). DOI:10.1016/j.tics.2014.02.002
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    ABSTRACT: Abstract Objective: This study examined the feasibility of a prototype Web-based acceptance and commitment therapy (ACT) program for preventing mental health problems among college students. Participants: Undergraduate first-year students (N = 76) participated between May and November 2011. Methods: Participants were randomized to ACT or a waitlist, with assessments conducted at baseline, posttherapy, and 3-week follow-up. Waitlist participants accessed the program after the second assessment. Results: Program usability/usage data indicated high program acceptability. Significant improvements were found for ACT knowledge, education values, and depression with ACT relative to waitlist. Subgroup analyses indicated that ACT decreased depression and anxiety relative to waitlist among students with at least minimal distress. Within the ACT condition, significant improvements were observed from baseline to 3-week follow-up on all outcome and process measures. Conclusions: Results provide preliminary support for the feasibility of a Web-based ACT prevention program.
    Journal of American College Health 01/2014; 62(1):20-30. DOI:10.1080/07448481.2013.843533
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    ABSTRACT: This study investigated the feasibility of using behavioral activation to treat enduring postbereavement mental health difficulties using a two-arm, multiple baseline design comparing an immediate start group to a delayed start group at baseline, 12-, 24-, and 36-weeks postrandomization. Participants received 12-14 sessions of behavioral activation within a 12-week intervention period starting immediately after the first assessment or after 12weeks for the delayed start group. Prolonged grief, posttraumatic stress, and depression symptoms were assessed as outcomes. Compared with no treatment, behavioral activation was associated with large reductions in prolonged, complicated, or traumatic grief; posttraumatic stress disorder; and depression symptoms in the intent-to-treat analyses. Seventy percent of the completer sample at posttreatment and 75 percent at follow-up responded to treatment with 45 percent at posttreatment and 40 percent at follow-up being classified as evidencing high-end state functioning at 12-week follow-up.
    Behavior therapy 12/2013; 44(4):639-650. DOI:10.1016/j.beth.2013.04.009
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    ABSTRACT: In grapheme-color synesthesia, graphemes (e.g., numbers or letters) evoke color experiences. It is generally reported that the opposite is not true: colors will not generate experiences of graphemes or their associated information. However, recent research has provided evidence that colors can implicitly elicit symbolic representations of associated graphemes. Here, we examine if these representations can be cognitively accessed. Using a mathematical verification task replacing graphemes with color patches, we find that synesthetes can verify such problems with colors as accurately as with graphemes. Doing so, however, takes time: ∼250ms per color. Moreover, we find minimal reaction time switch-costs for switching between computing with graphemes and colors. This demonstrates that given specific task demands, synesthetes can cognitively access numerical information elicited by physical colors, and they do so as accurately as with graphemes. We discuss these results in the context of possible cognitive strategies used to access the information.
    Consciousness and Cognition 10/2013; 22(4):1384-1392. DOI:10.1016/j.concog.2013.09.005
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    ABSTRACT: Color losses of central origin (cerebral achromatopsia and dyschromatopsia) can result from cortical damage and are most commonly associated with stroke. Such cases have the potential to provide useful information regarding the loci of the generation of the percept of color. One available tool to examine this issue is the chromatic visual evoked potential (cVEP). The cVEP has been used successfully to objectively quantify losses in color vision capacity in both congenital and acquired deficiencies of retinal origin but has not yet been applied to cases of color losses of cortical origin. In addition, it is not known with certainty which cortical sites are responsible for the generation of the cVEP waveform components. Here we report psychophysical and electrophysiological examination of a patient with color deficits resulting from a bilateral cerebral infarct in the ventral occipitotemporal region. Although this patient demonstrated pronounced color losses of a general nature, the waveform of the cVEP remains unaffected. Contrast response functions of the cVEP are also normal for this patient. The results suggest that the percept of color arises after the origin of the cVEP and that normal activity in those areas that give rise to the characteristic negative wave of the cVEP are not sufficient to provide for the normal sensation of color.
    Journal of Vision 08/2013; 13(10). DOI:10.1167/13.10.15
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    ABSTRACT: Grapheme-color synesthetes experience color, not physically present, when viewing symbols. Synesthetes cannot remember learning these associations. Must synesthetic percepts be formed during a sensitive period? Can they form later and be consistent? What determines their nature? We tested grapheme-color synesthete, MC2, before, during and after she studied Hindi abroad. We investigated whether novel graphemes elicited synesthetic percepts, changed with familiarity, and/or benefited from phonemic information. MC2 reported color percepts to novel Devanagari and Hebrew graphemes. MC2 monitored these percepts over 6months in a Hindi-speaking environment. MC2 and synesthete DN, reported synesthetic percepts for Armenian graphemes, or Cyrillic graphemes+phonemes over time. Synesthetes, not controls, reported color percepts for novel graphemes that gained consistency over time. Phonemic information did not enhance consistency. Thus, synesthetes can form and consolidate percepts to novel graphemes as adults. These percepts may depend on pre-existing grapheme-color relationships but they can flexibly shift with familiarity.
    Consciousness and Cognition 07/2013; 22(3):944-954. DOI:10.1016/j.concog.2013.06.002
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