Display variability and spatial organization as contributors to the pigeon's discrimination of complex visual stimuli

Three experiments assessed the contributions of display variability and spatial organization to the pigeon's discrimination of 16-icon visual displays. After training to discriminate 4 x 4 arrays of same and different computer icons, 4 pigeons were shown testing displays that systematically manipulated the variability of the depicted icons and their spatial organization on the display screen. Display variability and spatial organization each reliably controlled the pigeon's behavior. These seemingly separate effects could be collectively explained by the pigeon's discriminating the amount of variability or entropy in localized regions of the display.     

Timing and the Control of Rhythmic Upper-Limb Movements

Accurate timing of limb displacement is crucial for effective motor control. The authors examined the effects of movement velocity, duration, direction, added mass, and auditory cueing on timing, spatial, and trajectory variability of single- and multijoint rhythmic movements. During single-joint movements, increased velocity decreased timing and spatial variability, whereas increased movement duration increased timing variability but decreased spatial variability. For multijoint movements, regardless of condition, increasing velocity decreased joint timing, spatial, and trajectory variability, but all hand variabilities were unaffected by velocity, duration, load, or direction. Timing, spatial, and trajectory variability was greater at the shoulder compared with the elbow and minimal at the hand, supporting the notion that reaching movements are planned in hand space as opposed to joint space.     

Encoding of variability of landmark-based spatial information

Recent evidence suggests humans optimally weight visual and haptic information (i.e., in inverse proportion to their variances). A more recent proposal is that spatial information (i.e., distance and direction) may also adhere to Bayesian principles and be weighted in an optimal fashion. A fundamental assumption of this proposal is that participants encode the variability of spatial information. In a three-dimensional virtual-environment open-field search task, we provide evidence that participants encoded the variability of landmark-based spatial information. Specifically, participants searched for a hidden goal location in a 5 × 5 matrix of raised bins. Participants experienced five training phases in which they searched for a hidden goal that maintained a unique spatial relationship to each of four distinct landmarks. Each landmark was assigned an a priori value of locational uncertainty such that each varied in its ability to predict a goal (i.e., varied in number of potential goal locations). Following training, participants experienced conflict trials in which two distinct landmarks were presented simultaneously. Participants preferentially responded to the landmark with the lower uncertainty value (i.e., smaller number of potential goal locations). Results provide empirical evidence for the encoding of variability of landmark-based spatial information and have implications for theoretical accounts of spatial learning.     

Information entropy and the variability of space-time movement error

The authors investigated the effects of movement time and movement distance on the information entropy and variability of spatial and temporal error in a discrete aiming movement. In Experiment 1, the authors held movement distance (100 mm) constant and manipulated 11 movement times (300-800 ms) of 8 participants. In Experiment 2, the authors tested 6 movement distances at 2 given movement times (15-60 mm at 300 ms; 40-240 mm at 800 ms) in 8 participants. The variability and entropy for spatial error increased with average movement velocity, whereas the variability and entropy for temporal error decreased as a function of average movement velocity. The common variance between variable error and entropy averaged about 84% and 72% for spatial and temporal errors, respectively, suggesting that the probabilistic approach of entropy reveals features that are not present in the standard deviation index of variability. The findings provide further evidence that information entropy may be a useful single-index representation of variability in the movement speed-accuracy relation.     

Individual differences in cardiac vagal tone are associated with differential neural responses to facial expressions at different spatial frequencies: An ERP and sLORETA study

A previous study has shown that greater cardiac vagal tone, reflecting effective self-regulatory capacity, was correlated with superior visual discrimination of fearful faces at high spatial frequency Park et al. (Biological Psychology 90:171?C178, 2012b). The present study investigated whether individual differences in cardiac vagal tone (indexed by heart rate variability) were associated with different event-related brain potentials (ERPs) in response to fearful and neutral faces. Thirty-six healthy participants discriminated the emotion of fearful and neutral faces at broad, high, and low spatial frequencies, while ERPs were recorded. Participants with low resting heart rate variability??characterized by poor functioning of regulatory systems??exhibited significantly greater N200 activity in response to fearful faces at low spatial frequency and greater LPP responses to neutral faces at high spatial frequency. Source analyses??estimated by standardized low-resolution brain electromagnetic tomography (sLORETA)??tended to show that participants with low resting heart rate variability exhibited increased source activity in visual areas, such as the cuneus and the middle occipital gyrus, as compared with participants with high resting heart rate variability. The hyperactive neural activity associated with low cardiac vagal tone may account for hypervigilant response patterns and emotional dysregulation, which heightens the risk of developing physical and emotional problems.     

Functional equivalence of spatial representations derived from vision and language: evidence from allocentric judgments

Past research (e.g., J. M. Loomis, Y. Lippa, R. L. Klatzky, & R. G. Golledge, 2002) has indicated that spatial representations derived from spatial language can function equivalently to those derived from perception. The authors tested functional equivalence for reporting spatial relations that were not explicitly stated during learning. Participants learned a spatial layout by visual perception or spatial language and then made allocentric direction and distance judgments. Experiments 1 and 2 indicated allocentric relations could be accurately reported in all modalities, but visually perceived layouts, tested with or without vision, produced faster and less variable directional responses than language. In Experiment 3, when participants were forced to create a spatial image during learning (by spatially updating during a backward translation), functional equivalence of spatial language and visual perception was demonstrated by patterns of latency, systematic error, and variability.     

Spatial and object working memory impairments in schizophrenia patients: a Bayesian item-response theory analysis

This study reports evidence that schizophrenia patients are significantly impaired in both spatial and object (shape) working memory. A 3-s delay between exposure and recall of targets was used and Bayesian item-response theory was applied to compensate for the tasks' differential difficulty while simultaneously taking account of missing data from participant attrition. Weaker evidence was found that in schizophrenia both domains are equally impaired on average, that spatial and object working memory appear to be more highly correlated with each other in the schizophrenia population than in the normal population, and that schizophrenia patients show greater variability in spatial than object working memory performance.     

Learning a spatial skill for surgery: how the contributions of abilities change with practice

We examined changes in performance as people learned to use an angled laparoscope, a challenging spatial skill that must be mastered by surgeons who perform minimally invasive techniques. In Experiment 1, novices took tests of spatial and general reasoning ability, and then learned to operate an angled laparoscope, simulated in a virtual environment, over 12 learning sessions. Initial performance showed considerable variability among learners, with performance related to general and spatial abilities. As learning progressed, interindividual variability diminished and all learners attained proficiency; the correlation with general ability diminished but the correlation with spatial ability remained significant. In Experiment 2, performance by highly experienced surgeons on the simulation was excellent from the first session, confirming its ecological validity. The findings contribute to theories of skill acquisition. They also have practical implications for the selection of surgeons and for the potential use of virtual environments in surgical training. Copyright © 2006 John Wiley & Sons, Ltd.     

Gender differences in variability in intellectual abilities: A cross-cultural perspective

A cross-cultural quantitative review of contemporary findings of gender differences in variability in verbal, mathematical, and spatial abilities was conducted to assess the generalizability of U.S. findings that (a) males are more variable than females in mathematical and spatial abilities, and (b) the sexes are equally variable in verbal ability. No consistent gender differences (variance ratios) were found across countries in any of the three broad ability domains. Instead, males were more variable than females in some nations and females were more variable than males in other nations. Thus, the well-established U.S. findings of consistently greater male variability in mathematical and spatial abilities were not invariant across cultures and nations.I would like to thank Robert Linn for providing me with the British norms for the Differential Aptitude Tests and Julian Stanley for his comments on a draft of this article.     

Variability effects on the internal structure of rapid aiming movements

Two experiments are reported in which the effects of different levels of spatial variability of the initial phase of aiming movements were explored. It was found that longer, faster, and more spatially variable initial sub movements were associated with an almost proportional increase in the distance between the average location at which the first submovement ended and the target. The first experiment involved a multisegmental arm motion that required a direction reversal, in which spatial variability could be estimated in all three dimensions. The second was a unidirectional, one-degree-of-freedom wrist supination task. The variability-amplitude relationship for the initial submovement was present in both. It is argued that the variability, or unpredictability, of the initial submovement is a determinant of its average amplitude, such that initial submovements approach the target as closely as is permitted by the level of variability. Such a mechanism allows task constraints such as accuracy requirements and allowable error rates to be met most efficiently, in a manner similar to the recently described optimization of submovement durations. If this mechanism is a general, ubiquitous phenomenon in rapid aiming, certain features of its internal kinematic structure are predictable. A set of five such predictions is outlined.     

中文阅读中副中央凹预加工的范围与程度

在阅读中, 读者既能加工当前注视的中央凹视觉区的信息, 也能从副中央凹视觉区提取信息并利用该信息预先加工下文词汇, 称为预加工或预视。它是熟练阅读的一个关键环节。对副中央凹信息的预加工涉及预视的空间范围和预视程度(即预视量和预视类型)。在拼音文字阅读的研究中, 关于预视范围与预视程度如何受中央凹加工负荷和副中央凹预加工负荷的调节存在争议, 一个主要的原因是拼音文字词长变异大, 在考察预视程度时难以克服预视范围的干扰。而中文词长变化小, 能有效分离预视范围与预视程度。利用中文优势, 采用眼动技术来考察:(1)副中央凹预加工负荷如何影响预视范围, (2)中央凹加工负荷如何影响预视范围与预视程度, (3)阅读能力与阅读效率如何调节预视范围与预视程度, 结果将有助于解决副中央凹预视研究中的理论争论, 为预测阅读能力与衡量阅读效率提供更多有效的眼动行为指标。     

Optimal control strategies under different feedback schedules: kinematic evidence

Two experiments were conducted in which participants (N = 12, Experiment 1; N = 12, Experiment 2) performed rapid aiming movements with and without visual feedback under blocked, random, and alternating feedback schedules. Prior knowledge of whether vision would be available had a significant impact on the strategies that participants adopted. When they knew that vision would be available, less time was spent preparing movements before movement initiation. Participants also reached peak deceleration sooner but spent more time after peak deceleration adjusting limb trajectories. Consistent with those findings, analysis of spatial variability at different points in the trajectory indicated that variability increased up to peak deceleration but then decreased from peak deceleration to the end of the movement.     

Impulse and Movement Space-Time Variability

In 3 experiments, the authors examined movement space-time variability as a function of the force-time properties of the initial impulse in a movement timing task. In the range of motion and movement time task conditions, peak force, initial rate of force, and force duration were manipulated either independently or in combination across a range of parameter values. The findings showed that (a) impulse variability is predicted well by the elaboration of the isometric force variability scaling functions of L. G. Carlton, K. H. Kim, Y. T. Liu, and K. M. Newell (1993) to movement, and (b) the movement spatial and temporal outcome variability are complementary and well predicted by an equation treating the variance of force and time in Newton's 2nd law as independent random variables. Collectively, the findings suggest that movement outcome variability is the product of a coherent space-time function that is driven by the nonlinear scaling of the force-time properties of the initial impulse.     

Developmental course of auditory processing interactions: Garner interference and Simon interference.

Previous research suggests that with increasing age children become more efficient in inhibiting conflicting responses and in resisting interference from irrelevant information. We assessed the abilities of 100 children (ages 3-16 years) and 20 adults to resist interference during the processing of 2 auditory dimensions of speech, namely the speaker's gender and spatial location. The degree of interference from irrelevant variability in either dimension did not vary with age. Apparently, young children do not have more difficulty in resisting interference when the nontarget and the target are both perceptual attributes. We also assessed the participants' abilities to inhibit conflicting task-irrelevant information from spatial location and to resist interference from spatial variability in the context of conflict. In the presence of conflicting task-irrelevant information, both interference effects declined significantly with age. Developmental change in auditory processing seems to vary as a function of (1) the nature of the target-nontarget combination and (2) the presence/absence of conflicting task-irrelevant information.     

Strategic grouping in the spatial span memory task

Spatial short-term memory performance was examined in relation to participants' strategies. A total of 20 adult participants viewed and reproduced sequences of locations that varied in length (five, six, seven, or eight locations) and spatial separability (a manipulation of the configurations). In trial-by-trial self-reports, participants described five types of strategies. Chunking the spatial sequences into groups of three or four locations was the sole strategy associated with increased accuracy. Participants demonstrated considerable variability in the strategies that they selected, suggesting that cognitive resources are allocated to strategy selection, execution, and monitoring in the spatial span task. Spatially separable sequences were more accurately recalled than nonseparable sequences, independent of strategic grouping, suggesting two levels of grouping in the spatial span task.     

Strategic grouping in the spatial span memory task

Spatial short-term memory performance was examined in relation to participants’ strategies. A total of 20 adult participants viewed and reproduced sequences of locations that varied in length (five, six, seven, or eight locations) and spatial separability (a manipulation of the configurations). In trial-by-trial self-reports, participants described five types of strategies. Chunking the spatial sequences into groups of three or four locations was the sole strategy associated with increased accuracy. Participants demonstrated considerable variability in the strategies that they selected, suggesting that cognitive resources are allocated to strategy selection, execution, and monitoring in the spatial span task. Spatially separable sequences were more accurately recalled than nonseparable sequences, independent of strategic grouping, suggesting two levels of grouping in the spatial span task.     

Search Strategies in Practice: Movement Variability Affords Perception of Task Dynamics

Practice has been conceptualized in terms of a search process through an evolving perceptual-motor workspace. The experiment was set up to examine whether the inherent variability of the system would influence perception of the relevant properties of the task space. We reanalyzed the data from Hsieh, Liu, Mayer-Kress, and Newell (2013) in which participants performed a speed-accuracy aiming task and feedback emphasized either temporal or spatial accuracy in different conditions. The maximum variability in spatial error during practice differentiated individual's best performance in the fast speed-accuracy conditions. Additionally, we found that a threshold of variability predicted discontinuities during practice within individuals. The findings support the proposition that inherent variability affords perception of the relevant dimension of the task. The search motion through the perceptual-motor workspace was continuous or discontinuous depending on the constraints of the movement speed-accuracy condition.     

Anticipatory control of postural and task muscles during rapid arm flexion

A multicomponent pattern of premovement (anticipatory) activity in both task and postural muscles was examined for a unilateral rapid arm flexion movement (Belen'kii, Gurflnkel, & Pal'tsev, 1967) performed under simple visual reaction-time conditions. Subjects performed 30 right- and 30 left-side responses on each of four consecutive days. The anticipatory postural muscle activity may be considered a valid component of voluntary unilateral arm flexion. Invariances and variability in the spatial and temporal characteristics of the neuromuscular pattern are described in relationship to behavioral and motor control models of response organization. It is suggested that some temporal patterning among response components may not be preprogrammed centrally.     

A statistical decision model for sensory discrimination which predicts Weber’s law and other sensory laws: Some results of a computer simulation

A model for visual intensity threshold discrimination is described. Simplified assumptions represent the main features of the visual afferent paths. Discriminative responses are selected centrally by a statistical decision procedure, limited by the noise level. Noise arises from the irreducible physical variability of light, from spontaneous firing, and from variations in transmission in the afferent paths. These variations will tend to be positively correlated, The model was simulated on a computer: it correctly predicts the form of the Weber function (the relation between difference threshold and background intensity) and the features of spatial and temporal “summation”, It also shows that the function relating the eentral effeet of a stimulus to its physical intensity is unlikely to be logarithmic or a power function with a small exponent.     

Generation of Bimanual Trajectories of Disparate Eccentricity: Levels of Interference and Spontaneous Changes Over Practice

The authors examined intermanual interactions of 2 hands that were required to concurrently follow trajectories that differed in eccentricity. Ten healthy participants attempted to learn to trace 2 figures, a circle and an ellipse, with bilaterally isochronous (1:1) timing demands. Initial unimanual trials were followed by bilateral practice comprising 750 movement cycles. Two objectives were addressed: The authors' primary aim was to determine if kinematic interlimb interference is evident independent of spatial and temporal interference and to observe the potential practice-related changes in the nature of that interference. That test was afforded by participants' natural tendency to draw a circle with a relatively constant tangential velocity and an ellipse with a systematically varying velocity. A second aim was to observe the nature of spontaneous changes in the performance of each individual effector, and in the relationship between effectors, across practice. Those objectives were specifically addressed in a context in which augmented feedback was not available to direct the learners' attention to a particular feature of performance. The results suggested that interlimb assimilation of spatial features is the primary source of interference for that task and that apparent effects at the kinematic level are the secondary, indirect product of spatial coupling. Those results were found across blocks of practice. With respect to nondirected performance changes, substantially less improvement was evident in the performance of each individual effector than in the reduction of interlimb interference. Specifically, no practice-related changes in temporal variability or velocity bias, and minimal changes in trajectory smoothness, were evident in individual limbs. Conversely, significant reductions were observed in the variability of relative phase between limbs and in the magnitude of interlimb phase lag.