Effects of talker variability on speechreading

The effects of talker variability on visual speech perception were tested by having subjects speechread sentences from either single-talker or mixed-talker sentence lists. Results revealed that changes in talker from trial to trial decreased speechreading performance. To help determine whether this decrement was due to talker change--and not a change in superficial characteristics of the stimuli--Experiment 2 tested speechreading from visual stimuli whose images were tinted by a single color, or mixed colors. Results revealed that the mixed-color lists did not inhibit speechreading performance relative to the single-color lists. These results are analogous to findings in the auditory speech literature and suggest that, like auditory speech, visual speech operations include a resource-demanding component that is influenced by talker variability.     

空间距离对视觉工作记忆巩固的影响

以往研究发现,个体对不同类型的视觉信息进行视觉工作记忆巩固的模式存在差异,如对于方向信息,一次只能有一个项目被巩固进入视觉工作记忆系统,而对于颜色信息,个体则可以一次巩固两个项目进入视觉工作记忆系统。但对于视觉信息的巩固模式是否会受其他因素的影响,目前仍然没有明确的定论。本研究将探讨视觉信息的巩固模式是否可能受到记忆项目空间距离因素的影响。研究采用变化觉察范式、序列-同时呈现操作及控制记忆项目呈现间距的方法,通过3个实验考察记忆项目之间的空间距离是否能够影响个体对颜色信息和方向信息的巩固模式。在三种空间距离水平上序列呈现或同时呈现两个记忆项目,实验结果一致发现记忆项目之间的空间距离会对视觉工作记忆巩固模式产生明显影响,个体在同时呈现条件下的正确率会随着空间距离的增大而降低。这些结果表明对同一类视觉信息进行巩固的过程中所存在的项目数量限制并不是固定的,个体可以采用序列模式或有限容量的并行模式对同一类信息进行巩固,巩固的模式可能与视觉空间注意的分配以及视觉信息所能获得的注意资源有关。     

Effects of visual training on saccade control in dyslexia

This study reports the effects of daily practice of three visual tasks on the saccadic performance of 85 dyslexic children in the age range of 8 to 15 years. The children were selected from among other dyslexics because they showed deficits in their eye-movement control, especially in fixation stability and/or voluntary saccade control. Their eye movements were measured in an overlap prosaccade and a gap antisaccade task before and after the training. The three tasks used for the training included a fixation, a saccade, and a distractor condition. In any of these tasks, the subject had to detect the last orientation of a small pattern which rapidly changed its orientation between up, down, right, and left, before it disappeared after some time. The task was to press one of four keys corresponding to the last orientation. The visual pattern was presented on an LCD display of a small hand-held instrument given to the children for daily use at home. The results indicate that daily practice improved not only the perceptual capacity, but also the voluntary saccade control, within 3 to 8 weeks. After the training, the group of dyslexics was no longer statistically different from the control group.     

Are rats short-sighted? Effects of stimulus distance and size on visual detection

Behavioural evidence concerning short-sightedness in rats is apparently conflicting: in some experiments rats have performed poorly with visual stimuli further than about 60 cm distant, while in others they have made efficient use of more distant cues, for example to find their way through mazes. However, in the experiments suggesting short-sightedness, the physical size of the stimuli was not varied, so that stimulus distance and visual angle were confounded. In the present experiment, therefore, the size and distance of the stimuli to be detected were varied independently. Over the range tested (30-160 cm), distance was found to produce relatively slight effects on the smallest detectable visual angle, and these tended to diminish with practice. Thus, no good evidence was found for short-sightedness in rats up to 160 cm, a finding consistent with current views of the structure and image-forming capacities of the rat's eye. The smallest detectable targets were, however, surprisingly large in view of the rat's visual acuity (which is about 1c/deg): at the distances tested, animals required considerable training to run reliably to targets subtending less than 5-10° of visual angle. Difficulties in responding to stationary stimuli of this size are likely to restrict severely the use that rats make of vision both in the laboratory and in their natural surroundings.     

Early experience of Cued Speech enhances speechreading performance in deaf

It is known that deaf individuals usually outperform normal hearing subjects in speechreading; however, the underlying reasons remain unclear. In the present study, speechreading performance was assessed in normal hearing participants (NH), deaf participants who had been exposed to the Cued Speech (CS) system early and intensively, and deaf participants exposed to oral language without Cued Speech (NCS). Results show a gradation in performance with highest performance in CS, then in NCS, and finally NH participants. Moreover, error analysis suggests that speechreading processing is more accurate in the CS group than in the other groups. Given that early and intensive CS has been shown to promote development of accurate phonological processing, we propose that the higher speechreading results in Cued Speech users are linked to a better capacity in phonological decoding of visual articulators.     

Effects of delayed visual feedback on motor control performance

The effects of delay of visual feedback on two kinds of sensorimotor tasks were investigated. On the reciprocal tapping task, accuracy of performance decreased for 200, 500, and 767 msec. delay. The number of errors for the 1000-msec. delay is smaller than those for the other three conditions of delay. On the hand-writing task of both Kanji letters and English words, performance showed a large decrement with increasing delay. The most frequent kinds of error were the type of insertion of line elements or letter duplication. It was interesting that the size of written letters increased with lengthening delays of visual feedback.     

Effects of correct and transformed visual feedback on rhythmic visuo-motor tracking: tracking performance and visual search behavior

The effects of correct and transformed visual feedback on rhythmic unimanual visuo-motor tracking were examined, focusing on tracking performance (accuracy and stability) and visual search behavior. Twelve participants (reduced to 9 in the analyses) manually tracked an oscillating visual target signal in phase (by moving the hand in the same direction as the target signal) and in antiphase (by moving the hand in the opposite direction), while the frequency of the target signal was gradually increased to probe pattern stability. Besides a control condition without feedback, correct feedback (representing the actual hand movement) or mirrored feedback (representing the hand movement transformed by 180 degrees) were provided during tracking, resulting in either in-phase or antiphase visual motion of the target and feedback signal, depending on the tracking mode performed. The quality (accuracy and stability) of in-phase tracking was hardly affected by the two forms of feedback, whereas antiphase tracking clearly benefited from mirrored feedback but not from correct feedback. This finding extends previous results indicating that the performance of visuo-motor coordination tasks is aided by visual feedback manipulations resulting in coherently grouped (i.e., in-phase) visual motion structures. Further insights into visuo-motor tracking with and without feedback were garnered from the visual search patterns accompanying task performance. Smooth pursuit eye movements only occurred at lower oscillation frequencies and prevailed during in-phase tracking and when target and feedback signal moved in phase. At higher frequencies, point-of-gaze was fixated at a location that depended on the feedback provided and the resulting visual motion structures. During in-phase tracking the mirrored feedback was ignored, which explains why performance was not affected in this condition. Point-of-gaze fixations at one of the end-points were accompanied by reduced motor variability at this location, reflecting a form of visuo-motor anchoring that may support the pick up of discrete information as well as the control of hand movements to a desired location.     

Effects of training in visual discrimination after one year: visual analysis of volleyball skills.

Although the effects of specialized training in visual analysis of skills are well documented, whether the effects are lasting is not. The purpose of the present study was to analyze the effect a visual skills training program in volleyball had on participants one year after the completion of a training intervention. Subjects received either traditional performance instruction supplemented with visual training or traditional performance instruction in volleyball only. All subjects remaining in the teacher education program from a previous study were given a visual test on diagnosing errors in three different volleyball skills (the forearm pass, the overhead pass, and the overhead serve). Subjects exposed to visual training remained significantly better at diagnosing errors for the three volleyball skills one year later as compared to those subjects who had not received visual training.     

Target distance and adaptation in distance perception in the constancy of visual direction

Hay and Sawyer recently demonstrated that the constancy of visual direction (CVD) also operates for near targets. A luminous spot in the dark, 40 cm from the eyes, was perceived as stationary when S nodded his head. This implies that CVD takes target distance, as well as head rotation, into account as a stationary environment is perceived during head movements. Distance is a variable in CVD because, during a turning or nodding of the head, the eyes become displaced relative to the main target direction, the line between the target and the rotation axis of the head. This displacement of the eyes during head rotation causes an additional change in the target direction, i.e., a total angular change greater than the angle of the head rotation. The extent of this additional angular displacement is greater the nearer the target. We demonstrated that the natural combination of accommodation and convergence can supply the information needed by the nervous system to compensate for this additional target displacement. We also found that wearing glasses that alter the relation between these oculomotor adjustments and target distance produces an adaptation in CVD. An adaptation period of 1.5 h produced a large adaptation effect. This effect was not entirely accounted for by an adaptation in distance perception. Measurements of the alteration between oculomotor cues and registered distance with two kinds of tests for distance perception yielded effects significantly smaller than the effect measured with the CVD test. We concluded that the wearing of the glasses had also produced an adaptation within CVD.     

Numerical distance effects in visual search

We present three experiments in which observers searched for a target digit among distractor digits in displays in which the mean numerical target?Cdistractor distance was varied. Search speed and accuracy increased with numerical distance in both target-present and target-absent trials (Exp. 1A). In Experiment 1B, the target 5 was replaced with the letter S. The results suggest that the findings of Experiment 1A do not simply reflect the fact that digits that were numerically closer to the target coincidentally also shared more physical features with it. In Experiment 2, the numerical distance effect increased with set size in both target-present and target-absent trials. These findings are consistent with the view that increasing numerical target?Cdistractor distance affords faster nontarget rejection and target identification times. Recent neurobiological findings (e.g., Nieder, 2011) on the neuronal coding of numerosity have reported a width of tuning curves of numerosity-selective neurons that suggests graded, distance-dependent coactivation of the representations of adjacent numbers, which in visual search would make it harder to reject numerically closer distractors as nontargets.     

Calibrating reach distance to visual targets

The authors investigated the calibration of reach distance by gradually distorting the haptic feedback obtained when participants grasped visible target objects. The authors found that the modified relationship between visually specified distance and reach distance could be captured by a straight-line mapping function. Thus, the relation could be described using 2 parameters: bias and slope. The authors investigated whether calibration generalized across reach space with respect to changes in bias and slope. In Experiment 1, the authors showed that both bias and slope recalibrate. In Experiment 2, they tested the symmetries of reach space with respect to changes in bias. They discovered that reach space is asymmetric, with the bias shifting inward more readily than outward. The authors measured how rapidly the system calibrated and the stability of calibration once feedback was removed. In Experiment 3, they showed that bias and slope can be calibrated independently of one another. In Experiment 4, the authors showed that these calibration effects are not cognitively penetrable.