Lives as Collections of Strands: An Essay in Descriptive Psychology.

In this article I generalize the notion of multiple self-aspects to create a descriptive framework in which lives are partitioned into containers of activities called strands. Strands are nearly decomposable life modules, structured, stable, and concurrent longitudinal streams of extended duration whose momentary cross-sections constitute self-aspects. They are differentiated by five features: the person's role, the cast, the setting, norms and values, and habits and routines.

Questioning the automaticity of audiovisual correspondences.

An audiovisual correspondence (AVC) refers to an observer's seemingly arbitrary yet consistent matching of sensory features across the two modalities; for example, between an auditory pitch and visual size. Research on AVCs has frequently used a speeded classification procedure in which participants are asked to rapidly classify an image when it is either accompanied by a congruent or an incongruent sound (or vice versa). When, as is typically the case, classification is faster in the presence of a congruent stimulus, researchers have inferred that the AVC is automatic and bottom-up.

Competition between rhythmic and linguistic meaning revisited: the effect of task demands.

This paper revisits the conclusion of our previous work regarding the dominance of meaning in the competition between rhythmic parsing and linguistic parsing. We played five-note rhythm patterns in which each sound is a spoken word of a five-word sentence. We asked listeners to indicate the starting point of the rhythm while disregarding which word would normally be heard as the first word of the sentence.

Perceiving the initial note: quantitative models of how listeners parse cyclical auditory patterns.

In this paper, we explore the rules followed by the auditory system in grouping temporal patterns. Imagine the following cyclical pattern (which we call an "auditory necklace"-AN for short-because those patterns are best visualized as beads arranged on a circle) consisting of notes (1s) and rests (0s): … 1110011011100110 …. It is perceived either as repeating 11100110 or as repeating 11011100.

Dysrhythmia of timed movements in Parkinson's disease and freezing of gait.

A well-established motor timing paradigm, the Synchronization-Continuation Task (SCT), quantifies how accurately participants can time finger tapping to a rhythmic auditory beat (synchronization phase) then maintain this rhythm after the external auditory cue is extinguished, where performance depends on an internal representation of the beat (continuation phase). In this study, we investigated the hypothesis that Parkinson's disease (PD) patients with clinical symptoms of freezing of gait (FOG) exhibit exaggerated motor timing deficits. We predicted that dysrhythmia is exacerbated when finger tapping is stopped temporarily and then reinitiated under the guidance of an internal representation of the beat.

Competition between rhythmic and linguistic organization in a sentence-rhythm Stroop task.

We provide a test of Patel's [( 2003 ). Language, music, syntax and the brain. Nature Neuroscience, 6, 674-681] shared syntactic integration resources hypothesis by investigating the competition between determinants of rhythmic parsing and linguistic parsing using a sentence-rhythm Stroop task.

Deciphering the impact of cerebellar and basal ganglia dysfunction in accuracy and variability of motor timing.

Studies in motor timing have shown that the basal ganglia and cerebellum play an important role in temporal processing. Timing studies in Cerebellar/ataxic Disorders (CD) and Parkinson's disease (PD) patients contrast the roles of the cerebellum and basal ganglia in motor timing. Here, we used a synchronization-continuation task to compare accuracy and variability of motor timing during repetitive tapping.

A century of Gestalt psychology in visual perception: I. Perceptual grouping and figure-ground organization.

In 1912, Max Wertheimer published his paper on phi motion, widely recognized as the start of Gestalt psychology. Because of its continued relevance in modern psychology, this centennial anniversary is an excellent opportunity to take stock of what Gestalt psychology has offered and how it has changed since its inception. We first introduce the key findings and ideas in the Berlin school of Gestalt psychology, and then briefly sketch its development, rise, and fall.

Structural salience and the nonaccidentality of a Gestalt.

We perceive structure through a process of perceptual organization. Here we report a new perceptual organization phenomenon-the facilitation of visual grouping by global curvature. Observers viewed patterns that they perceived as organized into collections of curves.

Multistability, cross-modal binding and the additivity of conjoined grouping principles.

We present a sceptical view of multimodal multistability--drawing most of our examples from the relation between audition and vision. We begin by summarizing some of the principal ways in which audio-visual binding takes place. We review the evidence that unambiguous stimulation in one modality may affect the perception of a multistable stimulus in another modality.

Modeling accuracy and variability of motor timing in treated and untreated Parkinson's disease and healthy controls.

Parkinson's disease (PD) is characterized by difficulty with the timing of movements. Data collected using the synchronization-continuation paradigm, an established motor timing paradigm, have produced varying results but with most studies finding impairment. Some of this inconsistency comes from variation in the medication state tested, in the inter-stimulus intervals (ISI) selected, and in changeable focus on either the synchronization (tapping in time with a tone) or continuation (maintaining the rhythm in the absence of the tone) phase.

Grouping by Regularity and the perception of illumination.

The purpose of this work is to describe how the visual system groups surfaces of unequal lightness under complex patterns of illumination. We propose that the Gestalt principle of Grouping by Regularity explains this process better than the more often cited principle of Grouping by Similarity. In our first experiment we demonstrate that in a perceptual organization task, pitting proximity against illumination gradients, discounting the illuminant was contingent upon the periodicity of the illuminant.

Causality and cross-modal integration.

Schutz and Lipscomb (2007) reported an audiovisual illusion in which the length of the gesture used to produce a sound altered the perception of that sound's duration. This contradicts the widely accepted claim that the auditory system generally dominates temporal tasks because of its superior temporal acuity. Here, in the first of 4 experiments, we show that impact gestures influence duration ratings of percussive but not sustained sounds.

Visual determinants of a cross-modal illusion.

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, a sudden change of direction concurrent with tone onset) and (2) the illusion is controlled primarily by the duration of post-impact motion. Other aspects of the post-impact motion--distance traveled, velocity, acceleration, and the rate of its change (i.

The whole is equal to the sum of its parts: a probabilistic model of grouping by proximity and similarity in regular patterns.

The authors investigated whether the gestalt grouping principles can be quantified and whether the conjoint effects of two grouping principles operating at the same time on the same stimuli differ from the sum of their individual effects. After reviewing earlier attempts to discover how grouping principles interact, they developed a probabilistic model of grouping by proximity, which allows measurement of strength on a ratio scale. Then, in 3 experiments using dot lattices, they showed that the strength of the conjoint effect of 2 grouping principles--grouping by proximity and grouping by similarity--is equal to the sum of their separate effects.

Dissociation of early evoked cortical activity in perceptual grouping.

Perceptual grouping is a multi-stage process, irreducible to a single mechanism localized anatomically or chronometrically. To understand how various grouping mechanisms interact, we combined a phenomenological report paradigm with high-density event-related potential (ERP) measurements, using a 256-channel electrode array. We varied the relative salience of competing perceptual organizations in multi-stable dot lattices and asked observers to report perceived groupings.

The lawful perception of apparent motion.

Visual apparent motion is the experience of motion from the successive stimulation of separate spatial locations. How spatial and temporal distances interact to determine the strength of apparent motion has been controversial. Some studies report space-time coupling: If we increase spatial or temporal distance between successive stimuli, we must also increase the other distance between them to maintain a constant strength of apparent motion (Korte's third law of motion).

The economics of motion perception and invariants of visual sensitivity.

Neural systems face the challenge of optimizing their performance with limited resources, just as economic systems do. Here, we use tools of neoclassical economic theory to explore how a frugal visual system should use a limited number of neurons to optimize perception of motion. The theory prescribes that vision should allocate its resources to different conditions of stimulation according to the degree of balance between measurement uncertainties and stimulus uncertainties.

On the surprising salience of curvature in grouping by proximity.

The authors conducted 3 experiments to explore the roles of curvature, density, and relative proximity in the perceptual organization of ambiguous dot patterns. To this end, they developed a new family of regular dot patterns that tend to be perceptually grouped into parallel contours, dot-sampled structured grids (DSGs). DSGs are similar to the dot lattices used to study grouping by proximity, except that only one of the potential organizations is rectilinear; the others are curvilinear.

Stability and change in perception: spatial organization in temporal context.

Perceptual multistability has often been explained using the concepts of adaptation and hysteresis. In this paper we show that effects that would typically be accounted for by adaptation and hysteresis can be explained without assuming the existence of dedicated mechanisms for adaptation and hysteresis. Instead, our data suggest that perceptual multistability reveals lasting states of the visual system rather than changes in the system caused by stimulation.

Perceived complexity and the grouping effect in band patterns.

Symmetry properties have been shown to determine the perceived complexity of certain patterns. We used a paired-comparison method to obtain judgments of relative complexity for a family of two-dimensional regular patterns called band patterns. Although the complexity of these patterns is well predicted by their symmetry properties we were unable to explain an interaction observed between two of these properties for our experimental patterns.