Absence Of Feedback Research Articles

Ultrasound‐guided high intensity focused ultrasound therapy—Safety concerns from a clinical perspective.

The use of high intensity focused ultrasound (HIFU) in surgical applications has continued to grow at a rapid pace. Nevertheless, safety concerns limit the adoption of ultrasound guidance due to the persistent lack of real‐time monitoring and quantitative measures of clinical endpoints. Imaging and temperature estimation using magnetic resonance remains the preferred approach for guidance and monitoring in much of the Western world, while ultrasound imaging has seen wide use in China. Recent reviews of clinical outcomes have raised new regulatory concerns in China and are likely to increase scrutiny elsewhere. Still lacking are near real‐time measures of in situ parameters such as acoustic power, heating rate, or temperature, from which clinical endpoint metrics may be obtained with acceptable accuracy. Furthermore, therapy planning remains a semiquantitative process, producing highly variable results, particularly in the absence of feedback. This presentation provides an update on the clinical impact of insufficient quantification of ultrasound‐guided HIFU therapy.

The impact of studying in a second language (L2) medium university on the development of L2 writing

The number of international ESL students completing their degree programs in Australia has risen dramatically in the past decade. One factor that may be motivating students to undertake tertiary studies in Australia is the expectation that this form of immersion will lead to improved English language skills. However, existing research, such as research on the impact of study abroad programs on learners’ L2 skills, has produced mixed findings. Furthermore, most of this research has tended to focus on progress in L2 speaking skills. To date there has been very little research on the impact of living and studying in the L2 environment on learners’ L2 writing development. This paper reports on a study (part of a larger project) which used a test – re-test design to investigate changes, if any, in the learners’ academic writing after one semester of study in an L2-medium university. The writing scripts of 25 students who did not access the formal language support programs offered by the university were analysed using a range of qualitative and quantitative measures. The study found that after a semester of study at the university, the learners’ writing improved mainly in terms of structure and development of ideas. There was also some improvement in the formality of learners’ language, but there was no evidence of improvement in linguistic accuracy or complexity. Strategies used to incorporate source materials also remained largely unchanged, with learners continuing to copy verbatim from sources and acknowledging sources incorrectly. A number of factors are put forward to explain these findings. These factors include the short duration of the study (one semester) as well as perhaps the absence of feedback.

The Effect of Audio and Written Teacher Responses on EFL Student Revision

Providing feedback is one of the foreign language writing teacher's most important tasks (Ferris, 2007). However, there is less certainty about the techniques that should be used (K. Hyland & F. Hyland, 2006). This article reports on research that investigated the effects of two types of teacher feedback, on-tape and written, and of the absence of feedback on students' (n = 89) error correction. A comparison of the number of macro (content, organization) and micro (vocabulary, grammar, mechanics) errors before and after the experiment yielded a statistically significant reduction in the number of mistakes in final drafts. Students perceived the type of response received (either taped or written) had been helpful in revising their papers and considered the most beneficial aspect of teacher feedback to have been a focus on micro errors. This study offers insights into an ecclectic approach to teaching writing in similar EFL contexts.

The Effects of Cognitive Style and Feedback Type on Performance in an Internal Control Task

ABSTRACT: To facilitate the task of evaluating the internal control environment, auditors typically use internal control questionnaires (ICQ) to identify and document audit information. One drawback of structured ICQs is that beginning auditors charged with their completion could use them mechanistically, overlooking important cues that do not match ICQ prompts. We investigate the effects of cognitive style and feedback type on auditors' ability to identify internal control cues using ICQs. Student participants, proxying for beginning staff auditors with no experience, were classified as possessing either a sensor or an intuitive cognitive style. In an experiment, participants used an ICQ to identify internal control cues for one accounting cycle. After receiving varying kinds of feedback, participants repeated the internal control cue identification task using an ICQ for a second accounting cycle. Contrary to expectations, cognitive style did not significantly affect performance in the absence of feedback. As expected, significant associations between cognitive style and post-feedback task performance were found, with the combination of cognitive style and outcome feedback yielding positive performance improvements.

Linear eaters turned decelerated: Reduction of a risk for disordered eating?

It has been suggested that restrained eating is a cognitive strategy that an individual uses for control of food intake. If losing control, the restrained eater enters a state of disinhibition and is therefore thought to be at risk for developing eating disorders and obesity. Restrained eaters eat at a constant rate and can therefore also be referred to as linear eaters. Here, we have tested the hypothesis that restrained eating is a state that can be modified by teaching linear eaters to eat at a decelerated rate. Seventeen female linear eaters scored high on a scale for restrained eating. When challenged to eat at an increased rate, a test of disinhibition, the women overate by 16% on average. The women then practiced eating at a decelerated rate by use of feedback from a training curve displayed on a computer screen during the meals. The training occurred three times each week and lasted eight weeks. When re-tested in the absence of feedback, the women ate at a decelerated rate, they did not overeat in the test of disinhibition and they scored lower on the scale for restrained eating. It is suggested that restrained eating is a state that can be reduced by training.

Interplay of subthreshold activity, time-delayed feedback, and noise on neuronal firing patterns

Feedback connections and noise are ubiquitous features of neuronal networks and affect in a determinant way the patterns of neural activity. Here we study how the subthreshold dynamics of a neuron interacts with time-delayed feedback and noise. We use a Hodgkin-Huxley-type model of a thermoreceptor neuron and assume the feedback to be linear, corresponding effectively to a recurrent electrical connection via gap junctions. This type of feedback can model electrical autapses, which connect the terminal fibers of a neuron's axon with dendrites from the same neuron. Thus the delay in the feedback loop is due basically to the axonal propagation time. We chose model parameters for which the neuron displays, in the absence of feedback and noise, only subthreshold oscillations. These oscillations, however, take the neuron close to the firing threshold, such that small perturbations can drive it above the level for generation of action potentials. The resulting interplay between weak delayed feedback, noise, and the subthreshold intrinsic activity is nontrivial. For negative feedback, depending on the delay, the firing rate can be lower than in the noise-free situation. This is due to the fact that noise inhibits feedback-induced spikes by driving the neuronal oscillations away from the firing threshold. For positive feedback, there are regions of delay values where the noise-induced spikes are inhibited by the feedback; in this case, it is the feedback that drives the neuronal oscillations away from the threshold. Our study contributes to a better understanding of the role of electrical self-connections in the presence of noise and subthreshold activity.

Individual differences in auditory localization of real sources in the horizontal plane

Recent studies on spatial hearing showed that individual variability is greater with virtual sources than with real ones, but that sensorial feedback provides an efficacious and rapid learning procedure. This study evaluated the degree of inter-individual variability with real sound sources in the absence of feedback. Fifty normal-hearing listeners, aged 18-62, either left- or right handed, participated. The experiment was conducted in an anechoic room. One of twelve loudspeakers placed in the frontal horizontal plane and hidden by a curtain emitted a train of low-pass pulses. Listeners had to indicate the estimated direction of that source by placing a pointer on a screen. No feedback was given to them. Each listener completed 480-720 trials. Results indicated that variability between individual was great in both resolution in bias. Precisely, individuals differed (1) in the size of their maximum error, (2) in the azimuthal region in which this maximum error occurred, and (3) in the spatial symmetry of their performance. Indeed, 25% of the listeners showed significant left-right differences in their performance, these differences always favoring the left side of space. Such asymmetries have been noticed earlier but attributed to greater front-back confusions on the right, which cannot explain the present results.

Transmission of Progressive Images Over Noisy Channels: An End-to-End Statistical Optimization Framework

We present a statistical optimization framework for solving the end-to-end problem of multiple antenna transmission of progressive images over noisy channels. Such channels exhibit temporally correlated loss characteristics and are associated with wireless communication links. In our study, we protect the progressive bitstream associated with an image source utilizing a family of rate compatible punctured Reed-Solomon (RS) product codes along with receiver feedback. We consider the impacts of transmission bit errors as well as packet erasures. To cope with the impact of random bit errors, we formulate an optimization problem aimed at minimizing the end-to-end expected distortion of a reconstructed image subject to rate and efficiency constraints. In order to eliminate the impact of packet erasures, we propose utilizing an algorithm that is capable of statistically guaranteeing the delivery of a number of packet sets associated with a progressive bitstream. Our experiments capture the effects of embedding multiple antennas in the transmission of progressive images over wireless tandem channels. Under identical power constraints, our results show that increasing the number of antennas on either transmitting or receiving sides improves the quality of a reconstructed image. Further, the use of receive diversity used in conjunction with simple communication coding schemes such as maximum ration combining (MRC) yields more improvements than the use of transmit diversity used in conjunction with comparable communication coding schemes such as space-time block code (STBC). Finally, the use of receiver feedback can further improve the quality of an image reconstructed in the absence of feedback.

The effect of combined visual feedback and verbal encouragement on isokinetic concentric performance in healthy females

The purpose of this study was to compare isokinetic concentric quadriceps and hamstring performance in healthy females in the absence of feedback versus combined visual feedback and verbal encouragement at 60, 180 and 300 ◦ /s. A repeated-measures randomised cross-over design was used. Twenty two asymptomatic females were tested at the three test velocities under two randomly ordered conditions: (a) combined visual feedback and verbal encouragement; and (b) no feedback. The two sessions were separated by seven days. Examination of results revealed that with feedback there was a statistically significant increase in peak torque at the three test velocities ( p< 0.05) for both muscles. This study demonstrated that combined feedback can result in increased concentric muscle performance in females at three test velocities.

Effect of indirect information on system trust and control allocation¶

In contrast with most other experimental system trust research, this paper examines indirect information as a basis for trust. In experiment 1, the overall valence of an evaluation concerning a route planner was pitted against a consensus cue, i.e. a favourable opinion about the system endorsed by a minority versus a majority. A positive evaluation caused an increase of system trust, whereas a negative evaluation led to a decrease. Control allocation, i.e. choosing manual or automatic mode, however, remained unaffected. Furthermore, no effect was found of consensus; one explanation holds that, despite the absence of outcome feedback, displaying of routes on-screen provided interfering trust-relevant information. Focusing solely on the consensus effect in the absence of route display, experiment 2 revealed consensus to affect both trust and control allocation. These experiments show that trust-relevant information can be processed heuristically and systematically. Possibly, trust can also be based on direct information despite absence of feedback whether generated solutions are good or bad.

Linguistic Self‐Correction in the Absence of Feedback: A New Approach to the Logical Problem of Language Acquisition

In a series of studies children show increasing mastery of irregular plural forms (such as mice) simply by producing erroneous over-regularized versions of them (such as mouses). We explain this phenomenon in terms of successive approximation in imitation: Children over-regularize early in acquisition because the representations of frequent, regular plural forms develop more quickly, such that at the earliest stages of production they interfere with children's attempts to imitatively reproduce irregular forms they have heard in the input. As the strength of the representations that determine children's productions settle asymptotically, the early advantage for the frequent regular forms is negated, and children's attempts to imitate the irregular forms they have observed become more likely to succeed (a process that produces the classic U-shape in children's acquisition of plural inflection). These data show that children can acquire correct linguistic behavior without feedback in a situation where, as a result of philosophical and linguistic analyses, it has often been argued that it is logically impossible for them to do so.

Through the Looking Glass: How the Relationship between an Object and its Reflection Affects the Perception of Distance and Size

This is the first study to test the extent to which reflections help locate objects in space and perceive their size. For planar mirrors, the relative size of a target and its reflection is informative about the absolute distance of the target in units of the distance between target and mirror surface. When the target is near the mirror, target and reflection are similar in size; as the target moves away from the mirror, the difference in size increases. Observers saw a pair of objects in front of a mirror and judged relative size and distance (separately). Other visual cues to size and distance were eliminated, except lateral offset, which was tested in experiment 3. Experiment 2 controlled for the presence of directional feedback. Results showed orderly psychophysical functions for both size and distance with steeper slopes for distance judgments. In experiments 4 and 5 stereograms were used. Even when binocular information was present, the additional cue provided by reflections increased the accuracy of size and distance judgments. The same pattern of results was observed in the absence of feedback.

Why don't patients attend their appointments? Maintaining engagement with psychiatric services

Patients miss about 20% of scheduled appointments for mental health treatment, almost twice the rate in other medical specialties. Up to 50% of patients who miss appointments drop out of scheduled care. Many who miss appointments because of slips and lapses later rearrange their appointments without adverse consequences. Those that do not are at risk of further deterioration, relapse and hospital readmission. Predictors of non-attendance are complex and linked with the predictors of missed medication. Service barriers and administrative errors are common but are often overlooked in the absence of feedback from patients. Of prime importance are the therapeutic alliance and degree of ‘helpfulness’ of the clinician but again these are rarely measured routinely. Useful markers of engagement include patient-rated trust, satisfaction and degree of perceived participation in treatment decisions. Much can be done to improve attendance in most services. Simple measures such as offering prompt, convenient appointments, offering reminders and augmenting with telephone contact have a reasonable evidence base. Scales to assess therapeutic alliance are now available. Complex interventions need to be evaluated carefully in order that the overall benefits outweigh costs. We suggest that clinicians consider accessibility, discharge policies and patient feedback when examining local rates of non-attendance.

Backward Wave Excitation and Generation of Oscillations in Free-Electron Lasers in the Absence of Feedback—Beyond the High Gain Approximation

Quantum and free-electron lasers (FELs) are based on distributed interactions between electromagnetic radiation and gain media. In an amplifier configuration, a forward wave is amplified while propagating in a polarized medium. Formulating a coupled mode theory for excitation of both forward and backward waves, we identify conditions, leading to efficient excitation of backward wave without any mechanism of feedback or resonator assembly. The excitations of incident and reflected waves are described by a set of coupled differential equations expressed in the frequency domain. The induced polarization is given in terms of an electronic susceptibility tensor. In quantum lasers the interaction is described by two first-order differential equations. In FELs, the excitation of the forward and backward modes is described by two coupled third-order differential equations. In our previous investigation analytical and numerical solutions of reflectance and transmittance for both quantum lasers and high-gain FELs were presented. In this work we extend the study to a general FEL without restriction of the high-gain approximation. It is found that when the solutions become infinite, the device operates as an oscillator, producing radiation at the output with no Held at its input, entirely without any localized or distributed feedback.

On the Descriptive Value of Loss Aversion in Decisions under Risk

Previous studies of loss aversion in decisions under risk have led to mixed results. Losses appear to loom larger than gains in some settings, but not in others. The current paper clarifies these results by highlighting six experimental manipulations that tend to increase the likelihood of the behavior predicted by loss aversion. These manipulations include: (1) framing of the safe alternative as the status quo; (2) ensuring that the choice pattern predicted by loss aversion maximizes the probability of positive (rather than zero or negative) outcomes; (3) the use of high nominal (numerical) payoffs; (4) the use of high stakes; (5) the inclusion of highly attractive risky prospects that creates a contrast effect; and (6) the use of long experiments in which no feedback is provided and in which the computation of the expected values is difficult. In addition, the results suggest the possibility of learning in the absence of feedback: The tendency to select simple strategies, like ``maximize the worst outcome'' which implies ``loss aversion'', increases when this behavior is not costly. Theoretical and practical implications are discussed.

Rapid recalibration based on optic flow in visually guided action

Action capabilities are always subject to limits. Whether on foot or in a vehicle, people can only move so fast, slow down so quickly, and turn so sharply. The successful performance of almost any perceptual-motor task requires actors to learn and continually relearn their ever-changing action capabilities. Such learning can be considered an example of perceptual-motor calibration. The present study includes two experiments designed to address basic questions about the nature of this calibration process. Subjects performed a simulated braking task, using a foot pedal to slow down to a stop in front of an obstacle in the path of motion. At one point in the experiment, the strength of the brake was increased or decreased unbeknownst to subjects, and behavior before and after the change in brake strength was analyzed for evidence of recalibration. Experiment 1 showed that actors rapidly recalibrate following a change in brake dynamics, even when they are unaware of the change. In Experiment 2, the scene turned black one second after braking was initiated. Subjects still recalibrated following the change in brake strength, suggesting that information in the sensory consequences of the initial brake adjustment is sufficient for recalibration, even in the absence of feedback about the outcome (i.e., in terms of final position error) of the task. Discussion focuses on the critical but often overlooked role of calibration in continuously controlled visually guided action, and the nature of the information used for recalibration.

Multiple object juggling: Changing what is tracked during extended multiple object tracking

The multiple object tracking (MOT) task has been a useful tool for studying the deployment of limited-capacity visual resources over time. Since it involves sustained attention to multiple objects, this task is a promising model for real-world visual cognition. However, real-world tasks differ in two critical ways from standard laboratory MOT designs. First, in real-world tracking, it is unusual for the set of tracked items to be identified all at once and to remain unchanged over time. Second, real-world tracking tasks may need to be sustained over a period of minutes, and not mere seconds. How well is MOT performance maintained over extended periods of time? In four experiments, we demonstrate that observers can dynamically "juggle" objects in and out of the tracked set with little apparent cost, and can sustain this performance for up to 10 min at a time. This performance requires implicit or explicit feedback. In the absence of feedback, performance tracking drops steadily over the course of several minutes.

Chaotic stimulated Brillouin scattering near the threshold in a fiber with feedback

We investigate a nonlinear dynamical behavior of the stimulated Brillouin scattering (SBS) near the threshold in the presence of feedback. When a cw Nd:YAG laser is injected into a single mode optical fiber, the SBS signal exhibits intermittently appearing irregular self-pulsations near the threshold. By examining the time series of the SBS signals, we verify that spontaneous Brillouin scattering having a stochastic property is dramatically suppressed due to the feedback. We explain the chaotic phenomenon of SBS in the presence of feedback in comparison with that in the absence of feedback.

Chaotic stimulated Brillouin scattering near the threshold in a fiber

We investigate the nonlinear dynamic behavior of stimulated Brillouin scattering (SBS) near threshold in the absence of feedback. When a cw Nd:YAG laser is injected into a single-mode optical fiber, the SBS signal exhibits intermittently appearing irregular self-pulsations near the threshold. By examining the time series of the SBS signals, we verify that the irregular SBS signal is one of the chaotic phenomena appearing near the bifurcation point.

Bistability from double phosphorylation in signal transduction

Previous studies have suggested that positive feedback loops and ultrasensitivity are prerequisites for bistability in covalent modification cascades. However, it was recently shown that bistability and hysteresis can also arise solely from multisite phosphorylation. Here we analytically demonstrate that double phosphorylation of a protein (or other covalent modification) generates bistability only if: (a) the two phosphorylation (or the two dephosphorylation) reactions are catalyzed by the same enzyme; (b) the kinetics operate at least partly in the zero-order region; and (c) the ratio of the catalytic constants of the phosphorylation and dephosphorylation steps in the first modification cycle is less than this ratio in the second cycle. We also show that multisite phosphorylation enlarges the region of kinetic parameter values in which bistability appears, but does not generate multistability. In addition, we conclude that a cascade of phosphorylation/dephosphorylation cycles generates multiple steady states in the absence of feedback or feedforward loops. Our results show that bistable behavior in covalent modification cascades relies not only on the structure and regulatory pattern of feedback/feedforward loops, but also on the kinetic characteristics of their component proteins.