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We demonstrate that an irreducibly simple, uncontrolled, two-dimensional, two-link model, vaguely resembling human legs, can walk down a shallow slope, powered only by gravity. This model is the simplest special case of the passive-dynamic models pioneered by McGeer (1990a). It has two rigid massless legs hinged at the hip, a point-mass at the hip, and(More)
This paper discusses the mechanics of a rigid rimless spoked wheel, or regular polygon, 'rolling' downhill. By rolling, we mean motions in which the wheel pivots on one 'support' spoke until another spoke collides with the ground, followed by transfer of support to that spoke, and so on. We carry out three-dimensional numerical and analytical stability(More)
In brachiation, an animal uses alternating bimanual support to move beneath an overhead support. Past brachiation models have been based on the oscillations of a simple pendulum over half of a full cycle of oscillation. These models have been unsatisfying because the natural behavior of gibbons and siamangs appears to be far less restricted than so(More)
OBJECTIVE We investigated whether spatial working memory (WM) is associated with functional specialization of the right prefrontal cortex (PFC) relative to WM for shapes. We designed spatial and shape WM tasks that are relatively easy to perform and that minimize both task-switching and manipulation demands. The tasks use identical stimuli and require the(More)
Face recognition is thought to rely on configural visual processing. Where face recognition impairments have been identified, qualitatively delayed or anomalous configural processing has also been found. A group of women with Turner syndrome (TS) with monosomy for a single maternal X chromosome (45, Xm) showed an impairment in face recognition skills(More)
Historically, bipolar disorder and schizophrenia have been considered distinct disorders with different etiologies. Growing evidence suggests that overlapping genetic influences contribute to risk for these disorders and that each disease is genetically heterogeneous. Using cluster analytic methods, we empirically identified homogeneous subgroups of(More)
Women with Turner's syndrome (TS), who lack a complete X-chromosome, show an impairment in remembering faces and in classifying "fear" in face images. Could their difficulties extend to the processing of gaze? Three tasks, all of which rely on the ability to make use of the eye-region of a pictured face, are reported. Women with TS were impaired at judging(More)
Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI(More)
This study reports evidence that schizophrenia patients are significantly impaired in both spatial and object (shape) working memory. A 3-s delay between exposure and recall of targets was used and Bayesian item-response theory was applied to compensate for the tasks' differential difficulty while simultaneously taking account of missing data from(More)