David Gilden

University of Texas at Austin | UT · Department of Psychology

Objective: We use psychophysical methods to examine the maximum time intervals over which discrete events can be temporally integrated into the percept known as apparent motion. We hypothesized that the maximum time interval would be shorter in participants with attention deficit hyperactivity disorder (ADHD) than it would be in a control group....

Hilary Koprowski, MD, a distinguished and highly respected biomedical researcher, died on April 11, 2013 at the age of 96. Dr. Koprowski was best known for development of the first oral polio vaccine, for the currently used oral rabies vaccine, and for pioneering work in monoclonal antibodies to detect and treat cancer.

The perception of moment-to-moment environmental flux as being composed of meaningful events requires that memory processes coordinate with cues that signify beginnings and endings. We have constructed a technique that allows this coordination to be monitored indirectly. This technique works by embedding a sequential priming task into the event und...

The conditions for serial search are described. A multiple target search methodology (Thornton & Gilden, 2007) is used to home in on the simplest target/distractor contrast that effectively mandates a serial scheduling of attentional resources. It is found that serial search is required when (a) targets and distractors are mirror twins, and (b) whe...

Residual fluctuations produced in typical experimental methodologies are examined as correlated noises. The effective range of the correlations was assessed by determining whether the decay over look-back time is better described as a power law or exponential. Both of these decay laws contain free parameters and it is argued that it is not possible...

Attention-deficit hyperactivity disorder (ADHD) has been associated with anomalies in dopamine systems. Recent advances in the understanding of the core cognitive deficits in ADHD suggest that dopamine dysfunction might be expressed through shortened time scales in reward-based learning. Here this perspective is extended by the conjecture that temp...

1/f fluctuations have been discovered in a number of time series collected in psychological and behavioral experiments (e.g. Beltz & Kello, 2006, Gilden, 2001; Torre, Lemoine & Delignières, 2007). This ubiquity is per se an intriguing phenomenon, and the origin of such fluctuations remains in question. One considers that this very specific kind of...

Reaction times in a mental rotation task were measured across a diverse population that sorted into two groupings based on overall variability. Although both the low- and the high-variance groups produced data that displayed the trends typical of mental rotation, the two groups' reaction time sequences had very different autocorrelation functions....

A long-standing issue in the study of how people acquire visual information centers around the scheduling and deployment of attentional resources: Is the process serial, or is it parallel? A substantial empirical effort has been dedicated to resolving this issue (e.g., J. M. Wolfe, 1998a, 1998b). However, the results remain largely inconclusive bec...

Two distinct families of statistical processes are considered in the production of psychophysical time series data (Gilden, 1997, 2001; Gilden, Thornton, & Mallon, 1995). We inquire whether the spectral signatures of the underlying dynamics are better described in terms of short-range autoregressive moving-average (ARMA) processes or long-range fra...

Attentional constraints in the perceptual analysis of motion direction were examined using two independent paradigms: redundant target visual search and the analysis of fluctuations in discrimination accuracy at threshold. Results from both methods implied that directions of object motion are analyzed in parallel when those motions are translations...

The residual fluctuations that naturally arise in experimental inquiry are analyzed in terms of their time histories. Although these fluctuations are generally relegated to a statistical purgatory known as unexplained variance, this article shows that they may harbor a long-term memory process known as 1/f noise. This type of noise has been encount...

In 6 experiments, incidental memory was tested for direction of motion in an old-new recognition paradigm. Ability to recognize previously shown directions depended greatly on motion type. Memory for translation and expansion-contraction direction was highly veridical, whereas memory for rotation direction was conspicuously absent. Similar results...

Fluctuations in cognitive activity are examined in the three fundamental domains of psychophysical measurement: discrimination accuracy, reaction time latency, and production. Forced choice signal detection is found to be generally streaky; correct responses tend to be clustered. Clustering magnitude is maximal when attentional demand is minimized....

The nature of reaction time variability is analyzed in a suite of four experiments involving tasks, methodologies, and types of perceptual judgment commonly encountered in cognitive psychology In every case, a substantial fraction of the trial-by-trial variability in reaction time latency is shown to be well described by a particular type of fluctu...

Purpose. Local rotational motions generate weak memory encodings for direction relative lo expanding/contracting and translational motions. Similarly, people exhibit a general ineffectiveness in reasoning about rotational motions that does not exist with respect to translational motions. We were interested in determining if similar dissociations oc...

Observers judged the motion coherence of randomdot cinematograms Theoretical models were developed for coherence matches between cinematograms constructed from different angle distributions Evidence is presented that coherence matches are made on the basis of the Shannon-Wiener information entropy We show how the formal structure of information the...

Experiments in golf putting and darts demonstrated that skilled performance is streaky. The tendency for outcome sequences to form streaks was greatest when the task difficulty was such that about half the trials were successful. Mixtures of the two activities were also streaky, even when periodic interruption made the individual components resembl...

When a person attempts to produce from memory a given spatial or temporal interval, there is inevitably some error associated with the estimate. The time course of this error was measured in a series of experiments where subjects repeatedly attempted to replicate given target intervals. Sequences of the errors in both spatial and temporal replicati...

Human performance in the domain of signal detection is analyzed with respect to the formation of streaks. Streakiness was found to be a general property of auditory and visual discrimination in the sense that correct and incorrect responses have a positive sequential dependency. Success tends to follow success and failure tends to follow failure. L...

The logic of judging relative mass from a two-body collision is developed from data presented by Runeson and Vedeler (1993). Data from two experiments are analyzed on a point-by-point basis, and strong support for the theory that mass-ratio judgments are mediated by separate speed and angle heuristics is shown. This analysis is accomplished by redu...

The logic of judging relative mass from a two-body collision is developed from data presented by Runeson and Vedeler (1993). Data from two experiments are analyzed on a point-by-point basis, and strong support for the theory that mass-ratio judgments are mediated by separate speed and angle heuristics is shown. This analysis is accomplished by redu...

The aims of this project are to (1) develop a physiologically and psychophysically based model of low-level human visual processing (a key component of which are local frequency coding mechanisms), (2) develop image models and image-processing methods based upon local frequency coding, (3) develop algorithms for performing certain complex visual ta...

The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. The perceptual protocols that underlie discrimination between fractals and between other types of random contour and fractals are examined. Discrimination algorithms that have precisely the same sensitivities as...

The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. The perceptual protocols that underlie discrimination between fractals and between other types of random contour and fractals are examined. Discrimination algorithms that have precisely the same sensitivities as...

A series of experiments examined auditory contour formation, investigating listeners' sensitivities to a family of random fractals known as fractional Brownian noises. Experiments 1A and 1B looked at identification of contours when 3 different noises were portrayed using variations in the pitch, duration, or loudness of successive notes of a sequen...

Numerical simulations in one dimension with radiative losses approximately taken into account were conducted to evaluate the effectiveness of a hydrodynamical mechanism proposed to account for the ejection of bipolar flows from systems undergoing disk accretion. When radiative cooling is taken into account, the mechanism fails to accelerate matter...

An inquiry into the origins of dynamical awareness is conducted. Particular attention is given to a theory that postulates that impressions of dynamical quantities are derived from and structured by lawful physical relations. It is shown that impressions of dynamical quantities are not generally correlated with the values that these quantities take...

asked 124 subjects to simulate a series of 240 tosses of a fair coin / multiple regression analyses revealed that sequence generation is constrained by run length, the frequency of alternation, and the imbalance between heads and tails / these results are discussed in terms of the way subjects view the history of prior responses as they form future...

The short- and long-range apparent motion processes are discussed in terms of the statistical properties of images. It is argued that the short-range process, exemplified by the random-dot kinematogram, is primarily sensitive to the dipole statistics, whereas the long-range process, exemplified by illusory occlusion, is treated by the visual system...

The short- and long-range apparent motion processes are discussed in terms of the statistical properties of images. It is argued that the short-range process, exemplified by the random-dot kinematogram, is primarily sensitive to the dipole statistics, whereas the long-range process, exemplified by illusory occlusion, is treated by the visual system...

In two experiments we investigated people's ability to judge the relative mass of two objects involved in a collision. It was found that judgments of relative mass were made on the basis of two heuristics. Roughly stated, these heuristics were (a) an object that ricochets backward upon impact is less massive than the object that it hit, and (b) fas...

When making dynamical judgments, people can make effective use of only one salient dimension of information present in the event. People do not make dynamical judgments by deriving multidimensional quantities. The adequacy of dynamical judgments, therefore, depends on the degree of dimensionality that is both inherent in the physics of the event an...

In two experiments we investigated people's ability to judge the relative mass of two objects involved in a collision. It was found that judgments of relative mass were made on the basis of two heuristics. Roughly stated, these heuristics were (a) an object that ricochets backward upon impact is less massive than the object that it hit, and (b) fas...

When making dynamical judgments, people can make effective use of only one salient dimension of information present in the event. People do not make dynamical judgments by deriving multidimensional quantities. The adequacy of dynamical judgments, therefore, depends on the degree of dimensionality that is both inherent in the physics of the event an...

When making dynamical judgements, people can make effective use of o nly one salient dimension of information present in the event. People do not make dynamical judgements by deriving multidimensional quantities. Thus, the adequacy of dynamical judgements depends on the degree of dimensionality that is both 1) inherent in the physics of the event,...

In three experiments, we investigated apparent motion trajectories for stimuli flashed in different locations and at different orientations. It was found that, when stimuli were presented at different orientations, apparent motion trajectories were curved, although these paths were actually circular for only a restricted range of parameters. Curved...

Paracontrast and metacontrast magnitudes were measured in a target identification task. A particular class of illusory contours is described that did not mask in the paracontrast condition but did show a large metacontrast magnitude. The discontinuity in the masking function is interpreted in terms of the Fourier decomposition of the visual scene t...

A class of oscillations observed during eruption of dwarf novae has been interpreted as oscillations of the accretion disks in these systems.These oscillations are quasi-periodic with coherence times typically between three and 15 cycles. It is shown that magnetic field reconnection at high magnetic Reynolds number can drive disk oscillations. The...

The sampling errors that occur in the determination of the total volume and column density of mass at the solar position have been evaluated by analyzing simulated star catalogs as if they were observed sets of stars. The simulations were achieved by generating ensembles of stellar orbits that pass through the solar position in a realistic mass mod...

A computational technique is introduced which allows the student and researcher an opportunity to observe the physical behavior of a class of many-body systems. A series of examples is offered which illustrates the diversity of problems that may be studied using particle simulation. These simulations were in fact assigned as homework in a course on...

Differentially rotating accretion disks threaded by a uniform magnetic field have been numerically simulated. Fast reconnection followed by coalescence allows the magnetic field to drive small amplitude radial oscillations in the disk. These oscillations may be observable as the viscous stresses cause the disk to brighten and fade as the disk expan...

An ensemble of orbits passing through the solar position was generated for a specific mass model of the galaxy. These orbits are randomly sampled to form simulated density distributions of tracer stars perpendicular to the galactic disk. The simulated distributions are analyzed to determine the sampling errors in a self consistent derivation of the...

Gravitational radiation from the head-on collision of two identical compact stars is calculated using a two-dimensional, time-dependent, Newtonian hydrodynamical code. The star fluid is treated in an adiabatic approximation, and all relativistic effects are ignored. Gravitational radiation is computed as a small perturbation using linearized theory...

The cooling function for molecular gas is calculated, and it is found that in environments where CO cooling dominates, molecular gas may be thermally unstable. Two regimes of the condensation mode are isolated; isochorically cooling gas with temperature 10 < T < 200K and density n(H2) ⪉ 105cm-3, and thermally equilibrated gas with temperature 35 <...

Collisions between clumps in molecular clouds are studied in a series of numerical experiments employing a two-dimensional, time-dependent hydrodynamics code that includes self-gravity and an accurate cooling function. It is found that nonlinear effects are critical in the generation of gravitational instability and that linearized, normal mode ana...

There is abundant and diverse evidence that clumping is a common feature of molecular clouds. These observations have motivated a dynamical model of molecular clouds which views them as an ensemble of interacting clumps of gas. The primitive forms of clump interaction were studied through the technique of hydrodynamical simulation. The simplest int...

A fully relativistic hydrodynamics code which incorporates diffusive radiation transport is used to study time-dependent, spherically symmetric, optically thick accretion onto a black hole. It is found that matter free-falls into the hole regardless of whether the diffusion time scale is longer or shorter than the dynamical time. Nonadiabatic heati...

Although many researchers investigate the senses separately, most people have a coherent conscious experience of the world that is not divided into separate perceptions of vision, hearing, or other senses. The brain integrates the information received from our senses into a unified representation of the world around us. Previous research has demons...

A critical function of perception is the organization of temporally spaced input. This is accomplished through grouping, a process by which within-group elements are integrated with one another to form a cohesive unit. Grouping also requires boundaries to set off within-group elements from unrelated stimuli. In the temporal domain, grouping may be...