The role of eye movements in the missing-letter effect revisited with the rapid serial visual presentation procedure.

When participants read a text while searching for a target letter, they are more likely to miss the target letter embedded in frequent function words than in less frequent content words. This effect is usually observed with a text displayed normally, for which it has been found that frequent function words are fixated for a smaller amount of time than less frequent content words. However, similar pattern of omissions have been observed with a rapid serial visual presentation procedure in which words appear one at a time. These parallel results would demonstrate that fixation duration per se is not the proximal cause of the missing-letter effect only if eye movements are not made during the rapid serial visual presentation procedure. Therefore, the authors performed eye monitoring during the rapid serial visual presentation procedure. Results revealed that, with a rapid serial visual presentation procedure, participants fixated function and content words for almost the entire presentation duration. It is concluded that eye movements are not the proximal cause of the missing-letter effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of peripheral and central visual information for the directional control of manual aiming movements.

Seeing one's hand in visual periphery has been shown to optimize the directional accuracy of a sweeping hand movement, which is consistent with J. Paillard's (1980; Paillard and B. Amblard, 1985) two-channels model of visual information processing. However, contrary to this model, seeing one's hand in central vision, even for a brief period of time, also resulted in optimal directional accuracy. In 3 experiments, this study tested two opposing hypotheses proposed to explain the latter finding, and also determined whether additional support could be found for the existence of a visual kinetic channel. Results indicated that seeing one's hand in central vision, even for a very short delay, resulted in the same accuracy as being permitted to see one's hand for the duration of the whole movement. This suggests that seeing one's hand around the target might enable one to code its location and that of the target within a single frame of reference and, thus, facilitate movement planning. In addition, seeing one's hand in motion while in visual periphery permitted a better directional accuracy than when this information was not available, suggesting that the movement vector, which is planned prior to movement initiation, can be quickly updated following movement initiation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye-hand coordination: Oculomotor control in rapid aimed limb movements.

Three experiments are reported in which Ss produced rapid wrist rotations to a target while the position of their eyes was being monitored. In Experiment 1, Ss spontaneously executed a saccadic eye movement to the target around the same time as the wrist began to move. Experiment 2 revealed that wrist-rotation accuracy suffered if Ss were not allowed to move their eyes to the target, even when visual feedback about the moving wrist was unavailable. In Experiment 3, wrist rotations were equally accurate when Ss produced either a saccadic or a smooth-pursuit eye movement to the target. However, differences were observed in the initial-impulse and error-correction phases of the wrist rotations, depending on the type of eye movement involved. The results suggest that aimed limb movements use information from the oculomotor system about both the static position of the eyes and the dynamic characteristics of eye movements. Furthermore, the information that governs the initial impulse is different from that which guides final error corrections. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of visual and nonvisual feedback in a vehicle steering task.

This article investigates vehicle steering control, focusing on the task of lane changing and the role of different sources of sensory feedback. Participants carried out 2 experiments in a fully instrumented, motion-based simulator. Despite the high level of realism afforded by the simulator, participants were unable to complete a lane change in the absence of visual feedback. When asked to produce the steering movements required to change lanes and turn a corner, participants produced remarkably similar behavior in each case, revealing a misconception of how a lane-change maneuver is normally executed. Finally, participants were asked to change lanes in a fixed-based simulator, in the presence of intermittent visual information. Normal steering behavior could be restored using brief but suitably timed exposure to visual information. The data suggest that vehicle steering control can be characterized as a series of unidirectional, open-loop steering movements, each punctuated by a brief visual update. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimality in human motor performance: Ideal control of rapid aimed movements.

A stochastic optimized-submovement model is proposed for Fitts' law, the classic logarithmic trade-off between the duration and spatial precision of rapid aimed movements. According to the model, an aimed movement toward a specified target region involves a primary submovement and an optional secondary corrective submovement. The submovements are assumed to be programmed such that they minimize average total movement time while maintaining a high frequency of target hits. The programming process achieves this minimization by optimally adjusting the average magnitudes and durations of noisy neuromotor force pulses used to generate the submovements. Two new experiments on rapid wrist rotations yield additional support for the stochastic optimized-submovement model. Experiment 1 revealed that the mean durations of primary submovements and of secondary submovements, not just average total movement times, conform to a square-root approximation of Fitts' law derived from the model. Also, the spatial endpoints of primary submovements have standard deviations that increase linearly with average primary-submovement velocity, and the average primary-submovement velocity influences the relative frequencies of secondary submovements, as predicted by the model. During Experiment 2, these results were replicated and extended under conditions in which subjects made movements without concurrent visual feedback. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Symbolic control of visual attention: The role of working memory and attentional control settings.

This study examined how 1 symbol is selected to control the allocation of attention when several symbols appear in the visual field. In Experiments 1-3, the critical target feature was color, and it was found that uninformative central arrows that matched the color of the target were selected and produced unintentional shifts of attention (i.e., involuntary, initiated slowly, producing long-lasting facilitatory effects). Experiment 4 tested whether such selection is the result of an attentional filter or of a competition bias due to a match of incoming information against integrated object representations stored in working memory. Here, the critical feature was shape and color was irrelevant, but matching color arrows were still selected. Thus, features of objects in working memory will bias the selection of symbols in the visual field, and such selected symbols are capable of producing unintentional shifts of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of peripheral vision in the directional control of rapid aiming movements.

This study addresses the question of whether peripheral vision is involved in the control of hand trajectory direction during an aiming task performed at high speed. Ten adult subjects were required to aim at targets in various positions by making a punching movement with their hand. The experimental conditions were varied so that different parts of hand trajectory could be seen in the peripheral field. Two movement times were applied:     

On-line control of rapid aiming movements: Unexpected target perturbations and movement kinematics.

Two experiments with a total of 11 university students (aged 23–47 yrs) assessed the use of on-line visual information during rapid goal-directed aiming movements. In both experiments, participants were required to complete a discrete aiming movement to a single target on a graphics tablet. In Exp 1, during 76% of the experimental trials, the target width remained constant throughout the movement. The remaining 24% of the trials were evenly divided between 2 target perturbations in which the width of the target unexpectedly increased or decreased in size upon movement initiation. During Exp 2, the spatial location of the single target was perturbed to a new location closer to, or farther away from, the original target position. The proportion of perturbation trials remained constant across experiments. Results indicate that peak velocity was determined prior to movement initiation in order to meet the speed–accuracy demands of the original target width or movement amplitude. In contrast, during deceleration, participants modified their movement trajectories to account for a perturbation in target width or movement amplitude. These data suggest that on-line monitoring of visual information can be used to modify the latter half of a movement trajectory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control of rapid aimed hand movements: The one-target advantage.

A series of 8 experiments examined the phenomenon that a rapid aimed hand movement is executed faster when it is performed as a single, isolated movement than when it is followed by a second movement (the 1-target advantage). Three new accounts of this effect are proposed and tested: the eye movement hypothesis, the target uncertainty hypothesis, and the movement integration hypothesis. Data are reported that corroborate the 3rd hypothesis, but not the first 2 hypotheses. According to the movement integration hypothesis, the first movement in a series is slowed because control of the second movement may overlap with execution of the first. It is shown that manipulations of target size and movement direction mediate this process and determine the presence and absence of the 1-target advantage. Possible neurophysiological mechanisms and implications for motor control theory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Passive vs. active control of rhythmic ball bouncing: The role of visual information.

The simple task of bouncing a ball on a racket offers a model system for studying how human actors exploit the physics and information of the environment to control their behavior. Previous work shows that people take advantage of a passively stable solution for ball bouncing but can also use perceptual information to actively stabilize bouncing. In this article, we investigate (a) active and passive contributions to the control of bouncing, (b) the visual information in the ball's trajectory, and (c) how it modulates the parameters of racket oscillation. We used a virtual ball bouncing apparatus to manipulate the coefficient of restitution α and gravitational acceleration g during steady-state bouncing (Experiment 1) and sudden transitions (Experiment 2) to dissociate informational variables. The results support a form of mixed control, based on the half-period of the ball's trajectory, in which racket oscillation is actively regulated on every cycle in order to keep the system in or near the passively stable region. The mixed control mode may be a general strategy for integrating passive stability with active stabilization in perception–action systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dimensional analysis of motion: IX. Comparison of visual and nonvisual control of component movements.

Twelve Ss practiced a knob-turning control panel task while blindfolded, and another 12 without blindfolds. A final set of trials was run in which the visual conditions were reversed for the Ss. Time of travel (hand movement) to reach the knobs, and time of manipulation, were recorded electronically. For both components, the non-blindfold group did better; practice did not compensate for loss of vision. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional control of emotional distraction in rapid serial visual presentation.

Temperament research has highlighted the importance of attentional control in both emotion regulation and as a predictor of psychopathology. Enhanced susceptibility to emotional distraction is a key feature of mood disturbance. Whereas many studies have examined the influence of individual differences in anxiety on the disruptive effects of emotional distractors, individual differences in attentional control have been largely neglected. Here we examine, within healthy volunteers, the relative contributions of individual differences in self-reported anxiety and attentional control to distractibility caused by emotional or neutral faces distractors occurring prior to neutral face targets during rapid serial visual presentation. Participants with good attentional control were less affected by both neutral and emotional distractors than participants with poorer attentional control. More pronounced distraction deficits were seen for emotional relative to neutral distractors in individuals with poor attentional control. In contrast state anxiety was not associated with increased emotional distraction. Our findings suggest a protective role of attentional control mechanisms in minimizing the influence of emotional distraction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between visual attention and eye movements.

Experimental psychologists have recently amassed a great deal of evidence supporting the hypothesis that the visual system can select a particular location over other locations in the visual field for further analysis without overtly orienting the eyes to the selected location. At the same time, we know that during reading and scene perception, the eyes are overtly directed to new regions of the visual field every 200 to 300 msec on average. How are covert shifts of attention and overt movements of the eyes related during complex visual-cognitive tasks? The available evidence from studies of the perceptual span in reading suggests that attention is allocated asymmetrically around the fixation point, with more information acquired in the direction that the eyes are moving. Based on this evidence and evidence from explorations of eye movement control in reading, the author presents a tentative model of the relationship between attention and eye movements, called the Sequential Attention Model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Guidance of eye movements during conjunctive visual search: The distractor-ratio effect.

The distractor-ratio effect refers to the finding that search performance in a conjunctive visual search task depends on the relative frequency of two types or subsets of distractors when the total number of items in a display is fixed. Previously, Shen, Reingold, and Pomplun (2000) examined participants' patterns of eye movements in a distractor-ratio paradigm and demonstrated that on any given trial saccadic endpoints were biased towards the smaller subset of distractors and participants flexibly switched between different subsets across trials. The current study explored the boundary conditions of this tendency to flexibly search through a smaller subset of distractors by examining the influence of several manipulations known to modulate search efficiency, including stimulus discriminability (Experiment 1), within-dimension versus cross-dimension conjunction search and distractor heterogeneity (Experiment 2). The results indicated that the flexibility of visual guidance and saccadic bias exemplified by the distractor-ratio effect is a robust phenomenon that mediates search efficiency by adapting to changes in the relative informativeness of stimulus dimensions and features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Input control processes in rapid serial visual presentations: Target selection and distractor inhibition.

The attentional blink refers to the finding that the 2nd of 2 targets embedded in a stream of rapidly presented distractors is often missed. Whereas most theories of the attentional blink focus on limited-capacity processes that occur after target selection, the present work investigates the selection process itself. Identifying a target letter caused an attentional blink for the enumeration of subsequent dot patterns, but this blink was reduced when the dots shared their color with the target letter. In contrast, performance worsened when the color of the dots matched that of the remaining distractors in the stream. Similarity between the targets also affected competition between different sets of dots presented simultaneously within a single display. The authors conclude that the selection of targets from a rapid serial visual presentation stream is mediated by both excitatory and inhibitory attentional control mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aging on planning and implementing arm movements.

In Exps 1 and 2, aiming movements were performed with and without visual feedback in young and elderly adults. The initial (acceleration and deceleration phases) and secondary movement components were analyzed. Although deceleration phase accuracy decreased without visual feedback in both age groups, accuracy diminished as movement amplitude increased only in the elderly. This suggested that the elderly were more dependent on visual feedback to modify motor programs for longer duration movements. Velocity also increased less with increasing amplitude and target size in the elderly, which was related to impaired preprogramming (acceleration phase) and implementation (deceleration phase) of higher forces. This conclusion was confirmed directly in Exp 2 because only the deceleration phase was affected by the removal of a visual feedback of arm position when availability of visual information could not be predicted before movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A neural-network model enabling sensorimotor learning: application to the control of arm movements and some implications for speech-motor control and stuttering

Low-level motor control is defined as adapting an organism to the unique physical properties of its own limbs. The two-jointed arm serves to exemplify that effective low-level motor control demands a neurally medicated inversion of the dynamics, as well as of the kinematics, of a limb system. Reflex-like processing--that is, feedforword of either actual or predicted proprioceptive signals--is thereby assumed to be the principle of the dynamics control. As regards speech-motor control, the overall tool transformation is assumed to transform the force pattern of the articulatory muscles into speech sounds. Like the arm model, the vocal-tract transformation thus defined is also divided into two parts, namely the transformation relating the muscle forces to the mechanospatial states of the vocal tract (which is analogous to the forward dynamics including natural interarticulatory couplings), and the transformation relating the mechanospatial states to the speech sounds. Low-level speech-motor control, then, needs to invert both transformations, each of which can be learned by means of the self-imitation algorithm. Erroneous learning can fail to decouple interarticulatory coupling and therefore lead to abnormal feedback loops through the reflex-like operating neural network, which in turn can cause stuttering if audiophonatoric coupling is involved in learning.