Opposite effects of motion dynamics on the Ebbinghaus and corridor illusions.

We recently showed that motion dynamics greatly enhance the magnitude of certain size contrast illusions, such as the Ebbinghaus and Delboeuf illusions. Here, we extend our study of the effect of motion dynamics on size illusions through a novel dynamic corridor illusion, in which a single target translates along a corridor background. Across three psychophysical experiments, we quantify the effects of stimulus dynamics on the Ebbinghaus and corridor illusions across different viewing conditions.

Attention Combines Similarly in Covert and Overt Conditions.

Attention is classically classified according to mode of engagement into voluntary and reflexive, and type of operation into covert and overt. The first distinguishes whether attention is elicited intentionally or by unexpected events; the second, whether attention is directed with or without eye movements. Recently, this taxonomy has been expanded to include automated orienting engaged by overlearned symbols and combined attention engaged by a combination of several modes of function.

The Wandering Circles: A Flicker Rate and Contour-Dependent Motion Illusion.

Understanding of the visual system can be informed by examining errors in perception. We present a novel illusion-Wandering Circles-in which stationary circles undergoing contrast-polarity reversals (i.e.

Interactions of flicker and motion.

We present a series of novel observations about interactions between flicker and motion that lead to three distinct perceptual effects. We use the term flicker to describe alternating changes in a stimulus' luminance or color (i.e.

Combined attention controls complex behavior by suppressing unlikely events.

Attention enables behavior by modulating both sensory inputs and task goals. Combining attentional resources from both of those sources exerts qualitatively large effects on manual performance. Here we tested how combined attention was represented in sensory processing, as reflected by the P1 component and associated activity in the alpha band.

Where Is Your Attention? Assessing Individual Instances of Covert Attentional Orienting in Response to Gaze and Arrow Cues.

Humans spontaneously follow where others are looking. However, recent investigations suggest such gaze-following behavior during natural interactions occurs relatively infrequently, only in about a third of available instances. Here we investigated if a similar frequency of orienting is also found in laboratory tasks that measure covert attentional orienting using manual responses.

The Dynamic Ebbinghaus: motion dynamics greatly enhance the classic contextual size illusion.

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.

Dynamic illusory size contrast: a relative-size illusion modulated by stimulus motion and eye movements.

We present a novel size-contrast illusion that depends on the dynamic nature of the stimulus. In the dynamic illusory size-contrast (DISC) effect, the viewer perceives the size of a target bar to be shrinking when it is surrounded by an expanding box and when there are additional dynamic cues such as eye movements, changes in retinal eccentricity of the bar, or changes in the spatial position of the bar. Importantly, the expanding box was necessary but not sufficient to obtain an illusory percept, distinguishing the DISC effect from other size-contrast illusions.

Synesthetic grapheme-color percepts exist for newly encountered Hebrew, Devanagari, Armenian and Cyrillic graphemes.

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.

Form features provide a cue to the angular velocity of rotating objects.

As an object rotates, each location on the object moves with an instantaneous linear velocity, dependent upon its distance from the center of rotation, whereas the object as a whole rotates with a fixed angular velocity. Does the perceived rotational speed of an object correspond to its angular velocity, linear velocities, or some combination of the two? We had observers perform relative speed judgments of different-sized objects, as changing the size of an object changes the linear velocity of each location on the object's surface, while maintaining the object's angular velocity. We found that the larger a given object is, the faster it is perceived to rotate.

The effect of attention on context dependent synesthetic experiences.

Here we report the results of a brief experiment investigating the role of attention in mediating contextual effects on synesthetic experiences. Specifically, we examine a grapheme-color synesthete for whom the grapheme letter 'O' and number '0' are associated with two very different colors. We presented the grapheme '0' in an array of graphemes that provided ambiguous contextual cues, such that the same grapheme could be perceived either as the number '0' or as the letter 'O'.