We investigated changes in bias (preference for one response alternative) in signal detection when relative reinforcer frequency for correct responses varied across sessions. In Experiment 1, 4 rats responded in a two-stimulus, two-response identification procedure employing temporal stimuli (short vs. long houselight presentations). Relative reinforcer frequency varied according to a ...

We demonstrate a method to count small numbers of atoms held in a deep, microscopic optical dipole trap by collecting fluorescence from atoms exposed to a standing wave of light that is blue detuned from resonance. While scattering photons, the atoms are cooled by a Sisyphus mechanism that results from ...

This paper describes a 4.596 GHz frequency synthesis based on a 2.1 GHz solid mounted resonator (SMR) voltage-controlled oscillator (VCO). The SMR oscillator presents a chip size lower than 2 mm(2), a power consumption of 18.2 mW, and exhibits a phase noise of -89 dBc/Hz and -131 dBc/Hz at 2 ...

After prolonged viewing of a continuous periodic motion stimulus at frequencies around 10 Hz, observers experience a fleeting impression of reversed motion: the continuous Wagon Wheel Illusion (c-WWI). To account for this phenomenon it has been proposed that attentional mechanisms discretely sample motion information. Alternative accounts argue that the illusion ...

Edward Morley was an early member of the faculty of Western Reserve University in Cleveland. He was a very talented experimentalist who collaborated with Michelson of the Case School of Applied Science on the famous "Speed Of Light through the Ether" measurements in the 1880's. In the 1890's, Morley accomplished ...

The purpose of this study was to clarify the effects of nutrients on the gonadal development of male rats kept under constant darkness as a model of disturbed daily rhythm. In the present study we examined fat-soluble vitamins and their interactions in this test population. Four fat-soluble vitamins (vitamin A ...

We have studied the dynamics of quartz tuning fork resonators used in atomic force microscopy taking into account the mechanical energy dissipation through the attachment of the tuning fork base. We find that the tuning fork resonator quality factor changes even in the case of a purely elastic sensor-sample interaction. ...

The "centroid" explanation of the Müller-Lyer and similar illusions of extent supposes the perceptual positional shifts of the stimulus terminators in direction of the centers-of-masses of adjacent contextual flanks. In the present study, the validity of the assumption was tested in psychophysical examination of illusory figures comprising the Müller-Lyer wings ...

Previous studies have been unable to induce the Cutaneous Rabbit Effect (CRE) when the most likely perceived location of the illusory stimulus is on a non-continuous skin area. To determine whether the CRE could be elicited when each of the delivered stimuli were on non-continuous skin areas, we developed a ...

Right brain damaged patients with left spatial neglect typically bisect long horizontal lines to the right of their midpoint. However, bisections of very short lines can favour the emergence of a paradoxical "cross-over" effect in which lines are bisected to the left of the true midpoint. It has been suggested that ...

Individuals in different contexts are referred to as "heroes" for seemingly different reasons. To better understand how and why people use this term, three studies were conducted. Approaching the question deductively, individuals defined the term "hero" and responses were coded according to existing definitions. Then, a definition of hero was ...

According to the Oppel-Kundt illusion, a filled space appears larger than an empty one. In the present research we studied how textural characteristics affect the perceived size of two-dimensional patterns. We investigated the perceived extension of square textures by manipulating spatial frequency and filling microelements' numerosity. Subjects compared the test ...

Cast shadows can be salient depth cues in three-dimensional (3D) vision. Using a motion illusion in which a ball is perceived to roll in depth on the bottom or to flow in the front plane depending on the slope of the trajectory of its cast shadow, we investigated cortical mechanisms ...

In a number of experiments, blindfolded subjects traced convex curves whose verticals were equal to their horizontal extent at the base. Overestimation of verticals, as compared with horizontals, was found, indicating the presence of a horizontal-vertical illusion with haptic curves, as well as with visible curves. Experiment 1 showed that ...

Simultaneous direction repulsion (the direction illusion) occurs in bidirectional motion displays, typically transparent motion random dot kinematograms. Several laboratories have reported a greatly reduced illusion with dichoptic presentation of the two coherently translating stimuli as compared to monocular or binocular presentation. Some researchers have argued that those results might be ...

We examine the time course of visual grouping and figure-ground processing. Figure (contour) and ground (random-texture) elements were flickered with different phases (i.e., contour and background are alternated), requiring the observer to group information within a pre-specified time window. It was found this grouping has a high temporal resolution: less ...

Music ensemble playing relies heavily on a conductor's gestural cues. Visibility of those cues varies within the ensemble, so conductors typically use compensation strategies selectively to improve the clarity of their gestures for different players. Currently, there are no quantitative studies evaluating the efficacy of such compensatory strategies. The present ...

Thermohaline intrusions have intrigued physical oceanographers since the first XBT section was published by Spilhaus in 1939. Characterized by vertical gradients of temperature and salinity having compensating density effects, intrusions are meters to tens of meters thick and extend laterally for hundreds of meters to many kilometers. Boundaries often have ...

A central bar presented in counterphase with two flanking bars creates the perception of only two bars, instead of three, flickering (standing wave of invisibility illusion). Current explanations of this illusion highlight the importance of local interactions between the central bar and the flankers as a reason for the invisibility ...

Orthographic frontal/back projections of biological-motion figures are bistable: The point-light figure in principle can be perceived either as facing toward the viewer or as facing away from the viewer. Some point-light actions--for example, walking--elicit a strong "facing bias": Despite the absence of objective cues to depth, observers tend to interpret ...

Neuronal oscillations are an essential part of several brain processes like perception, memory and attention, but little is known about the simultaneous dynamics of different frequency bands in such processes. Here, we studied the low- and high-frequency dynamics of neuronal oscillations in a task that involves covert searching and visual ...

Individuals exposed to both an increase in magnitude and a rotation of the gravitoinerital acceleration vector experience changes in visual and auditory localization and apparent body orientation. These effects are known as the oculogravic, audiogravic and somatogravic illusions, respectively. In our main experiment, we measured the magnitude, direction, and time ...

Differences between target and flanker orientations become exaggerated in the tilt illusion. However, small differences sometimes go unnoticed. This small-angle assimilation shares many similarities with other types of visual crowding but is typically found only with small and/or hard-to-see stimuli. In Experiment 1, we investigated the effect of stimulus visibility ...

The midpoint of the axis of bisection in a triangle appears to be displaced toward the apex so that the apical extent seems to be shorter than the basal extent, an effect originally reported in 1895 by Thiéry and later in 1898 by Wundt and, therefore, referred to here as ...

A new motion illusion based on dot-trajectory misperception is presented. The illusory effect can not be explained by the aperture problem unlike some previous illusions characterised by misperception of motion direction. We propose an explanation in terms of 'perceptual compromise' between an original type of apparent motion and the veridical ...

The origin of motion illusions in simple black and white patterns such those as used by Op artists has been at the center of a lively scientific debate, relating motion processing mechanisms to involuntary eye movements that generate characteristic motion patterns. To overcome the limitations of using subjective ratings as ...

Figure-ground assignment to a contour is a fundamental stage in visual processing. The current paper introduces a novel, highly general dynamic cue to figure-ground assignment: "Convex Motion." Across six experiments, subjects showed a strong preference to assign figure and ground to a dynamically deforming contour such that the moving contour ...

BACKGROUND: Altering the normal association between touch and its visual correlate can result in the illusory perception of a fake limb as part of our own body. Thus, when touch is seen to be applied to a rubber hand while felt synchronously on the corresponding hidden real hand, an illusion ...

We describe a compelling motion illusion elicited by a huge billboard placed along a street, depicting a building that contains strong perspective cues. When observers move fast along the opposite sidewalk, they perceive the depicted building as rotating in their direction of travel. This is a special case of the ...

Determining how the visual system locates moving stimuli continues to be an experimental and theoretical challenge. By making a moving visual stimulus equiluminant with its background, and immersing it in luminance noise, the spatial lead it normal enjoys over a flashed stimulus (the flash-lag illusion) was completely eliminated (the illusion ...

We report a new illusion in which the edges of diamonds placed at the intersections of grids are perceived to be jaggy (the jaggy diamonds illusion). Interestingly, the illusion disappears when the stimulus is rotated by 45 degrees, when the stimuli are observed at a close distance, and on the ...

Abstract. Perceived occlusion at T-junctions or illusory contours at implicit T-junctions are often modelled by using edge information without surface context. We explored the effect of closure on perceived occlusion at T-junctions. Two vertical lines separated by a gap each had six abutting horizontal lines on opposite sides forming T-junctions. ...

BACKGROUND: In rubber hand illusions and full body illusions, touch sensations are projected to non-body objects such as rubber hands, dolls or virtual bodies. The robustness, limits and further perceptual consequences of such illusions are not yet fully explored or understood. A number of experiments are reported that test the ...

In humans, sensory afferences are combined and integrated by the central nervous system (Ernst MO, Bülthoff HH (2004) Trends Cogn. Sci. 8: 162-169) and appear to provide a holistic representation of the environment. Empirical studies have repeatedly shown that vision dominates the other senses, especially for tasks with spatial demands. ...

Bigger objects look heavier than smaller but otherwise identical objects. When hefted as well as seen, however, bigger objects feel lighter (the size-weight illusion), confirming that the association between visual size and weight has a perceptual component. Darker objects also look heavier than brighter but otherwise identical objects. It is ...

An illusion of motion can be induced by presenting a horizontal line suddenly between two visual markers. If one marker is briefly illuminated (the "cue") prior to the appearance of the line, the line appears to spread from the cue toward the other marker. This is termed the line-motion illusion, ...

We question a central premise upon which the target article is based. Namely, we point out that the evidence for "positive illusions" is in fact quite mixed. As such, the question of whether positive illusions are adaptive from an evolutionary standpoint may be premature in light of the fact that ...

This commentary highlights the distinction between belief and pragmatic acceptance, and asks whether the positive illusions discussed in section 13 of the target article may be judicious pragmatic acceptances rather than adaptive misbeliefs. I discuss the characteristics of pragmatic acceptance and make suggestions about how to determine whether positive illusions ...

The mere fact that a particular aspect of mind could offer an adaptive advantage is not enough to show that that property was in fact shaped by that adaptive advantage. Although it is possible that the tendency towards positive illusion is an evolved misbelief, it it also possible that positive ...

Real lines and illusory contours (ICs) have been reported to either interfere with or facilitate the perception of the other, depending on real line orientation and contrast. Here we investigate contextual effects of real lines on illusory contour perception. Curvature discrimination thresholds of Kanizsa-contours were measured for superimposed real lines ...

We enjoy the illusion that visual resolution is high across the entire field of vision. However, this illusion can be easily dispelled by trying to identify objects in a cluttered environment out of the corner of your eye. This reflects, in part, the well-known decline in visual resolution in peripheral ...

Contrary to the predictions of established theory, Schutz and Lipscomb (2007) have shown that visual information can influence the perceived duration of concurrent sounds. In the present study, we deconstruct the visual component of their illusion, showing that (1) cross-modal influence depends on visible cues signaling an impact event (namely, ...

The watercolor effect (WCE) is a long-range color assimilation effect occurring within an area enclosed by a light chromatic contour, which in turn is surrounded by a dark chromatic contour. Here, we studied the effects of chromatic modulation of the WCE for different kinds of spacing between and within the ...

We have employed the shape frequency and shape-amplitude after-effects (SFAE and SAAE) to investigate: (i) whether the shapes of illusory and real curves are processed by the same or different mechanisms, and (ii) the carrier-tuning properties of illusory curvature mechanisms. The SFAE and SAAE are the phenomena in which adaptation ...

Pointing movements made to a target defined by the imaginary intersection of a pointer with a distant landing line were examined in healthy human observers in order to determine whether such motor responses are susceptible to the Poggendorff effect. In this well-known geometric illusion observers make systematic extrapolation errors when ...

Nakamura, Fujita, Ushitani, & Miyata (2006) have shown that pigeons perceive the standard Müller-Lyer illusion. In this report, the authors examined effects of bracket sizes on perception of this illusion in pigeons (Columba livia) and humans (Homo sapiens). In Experiment 1, three pigeons were retrained to classify six lengths of ...

In their recent article, Anderson and Winawer (2005) presented a dramatic lightness illusion in which identical texture patches appear to be either black or white. Albert (2007) argued that the Anderson and Winawer (2005) illusion can be explained by a simple theory in which occlusion cues determine the depth relationships ...

Perceived duration is conventionally assumed to correspond with objective duration, but a growing literature suggests a more complex picture. For example, repeated stimuli appear briefer in duration than a novel stimulus of equal physical duration. We suggest that such duration illusions appear to parallel the neural phenomenon of repetition suppression, ...

Nineteen psychology undergraduates were requested to "grasp" the lines of a computer image of Titchener's perpendicular with a thumb and index finger pincer grip immediately after the line to be grasped had been indicated and the whole figure extinguished. The hand remained visible. Lines were of three different lengths (6.5, ...

In the occlusion illusion, the visible portion of a partly occluded object appears larger than a physically identical nonoccluded region. Stereoscopic displays allowed for a direct test of the apparent-distance hypothesis. In Experiments 1A and 1B, we measured both the perceived size and the perceived depth of partly occluded targets ...