Detection of one-, two-, and three-dimensional Markov constraints in visual displays II: Multistate displays.

The study of the depth of visual information processing is here extended to multistate displays. Two classes of variables are distinguished: display variables which may either be fixed at a single level or varied over its possible levels, e.g., a numeric character, its brightness, and its orientation; and spatial-temporal variables which assume all possible states within each display, e.g., the x- and y-coordinates of the display, and the time-coordinate, t, representing successive frames of the display. Information was encoded in terms of constraints upon combinations of variables. Excellent discrimination is achieved for detecting constraints among two, but not three, display variables; or for detecting constraints among one, but not two, display variables and up to three spatial-temporal variables. Comparisons are made with previous tests of the depth of visual information processing with binary-coded materials within the spatial-temporal microstructure of the display.     

Achieving Coordination in Prehension: Joint Freezing and Postural Contributions

The focus of the present study was on the intersegmental relationships that emerge when both task and oganismic constraints are imposed upon the coordination system. Seven right-handed subjects were required to reach and grasp a cup (hand transport phase) and place it on a designated target (cup transport phase), using either their preferred or nonpreferred hand. The kinematics of the movement were examined as a function of task (grasping a full cup versus grasping an empty one) and organismic (preferred or nonpreferred hand) constraints. During the hand transport phase, a task constraint effect was revealed through an increase in the low-velocity phase for the full cup condition. This constraint coexisted with a decrease in angular motion of the shoulder and elbow joints, indicating subjects reduced the number of variables to be independently controlled in the final homing-in stage of the movement. Accompanying this decrease in angular change was an increase in the displacement of the trunk. During the cup transport phase, the trunk was shown to contribute significantly more to the movement in the full cup condition and for the left hand movements, thereby increasing the stability of the movement system. These findings are in agreement with Bernstein's (1967) notion of fixating parts of the body as an initial solution to a movement problem, and they lend support to the concept of a proximodistal organization of coordination.     

Limits on learning phonotactic constraints from recent production experience

Adults can learn new artificial phonotactic constraints by producing syllables that exhibit the constraints. The experiments presented here tested the limits of phonotactic learning in production using speech errors as an implicit measure of learning. Experiment 1 tested a constraint in which the placement of a consonant as an onset or coda depended on the identity of a nonadjacent consonant. Participant speech errors reflected knowledge of the constraint but not until the 2nd day of testing. Experiment 2 tested a constraint in which consonant placement depended on an extralinguistic factor, the speech rate. Participants were not able to learn this constraint. Together, these experiments suggest that phonotactic-like constraints are acquired when mutually constraining elements reside within the phonological system.     

Alliances,Domestic Politics,and Leader Psychology: Why Did Britain Stay Out of Vietnam and Go into Iraq?

In the Vietnam and Iraq conflicts, British Prime Ministers were asked to contribute forces to an American‐led war that was deeply unpopular in the United Kingdom. This presented Harold Wilson and Tony Blair with conflicting incentives and constraints: to support their senior ally or to make policy based upon domestic considerations. Why did Harold Wilson decline to commit British forces while Tony Blair agreed to do so? With situational factors generating conflicting predictions, I argue that investigation of individual‐level variables is necessary. In particular, I suggest that leaders vary systematically in their willingness to subordinate the concerns of constituents to strategic imperatives, and that introducing the leadership style categories of “constraint challenger” and “constraint respecter” can make more determinate the linkage between domestic politics and strategic concerns.     

Analogical Mapping by Constraint Satisfaction

A theory of analogical mapping between source and target analogs based upon interacting structural, semantic, and pragmatic constraints is proposed here. The structural constraint of isomorphism encourages mappings that maximize the consistency of relational corresondences between the elements of the two analogs. The constraint of semantic similarity supports mapping hypotheses to the degree that mapped predicates have similar meanings. The constraint of pragmatic centrality favors mappings involving elements the analogist believes to be important in order to achieve the purpose for which the analogy is being used. The theory is implemented in a computer program called ACME (Analogical Constraint Mapping Engine), which represents constraints by means of a network of supporting and competing hypotheses regarding what elements to map. A cooperative algorithm for parallel constraint satisfaction identities mapping hypotheses that collectively represent the overall mapping that best fits the interacting constraints. ACME has been applied to a wide range of examples that include problem analogies, analogical arguments, explanatory analogies, story analogies, formal analogies, and metaphors. ACME is sensitive to semantic and pragmatic information if it is available, and yet able to compute mappings between formally isomorphic analogs without any similar or identical elements. The theory is able to account for empirical findings regarding the impact of consistency and similarity on human processing of analogies.     

Progamming time in serial tapping responses as a function of pathway constraint

Summary This study varied the accuracy demand within a linear series of targets to investigate the effect of movement-pathway constraints on response-programming time. Sidaway, Christina, and Shea (1988) have suggested that constraints placed upon movement initiation by the demand for response precision may play an important role in determining the length of the programming process. By varying the subtended angles of a series of three targets, this experiment tested the specific prediction of Sidaway et al. that programming time may be a function of the target, within a line of targets, that subtends the smallest angle at the start position. It is this target that demands the greatest precision in the movement pathway. Subjects participated in a series of conditions in which the size and placement of the target that imposed the maximal constraint was varied. In each condition the subjects were required to strike a series of three targets with a stylus in a simple reaction-time paradigm. Analysis of the reaction-time results revealed a significant effect of size of constraint, but no effect of position of constraint. Analysis of the movementtime data dispelled movement-duration and movement-velocity interpretations of the results and intimated a possible online trajectory-correction process.Portions of these data were first presented at the Annual Meeting of the Psychonomic Society in Atlanta, Georgia, November 1989.     

“Center-of-gravity” Tendencies for fixations and flow patterns

Fixation positions were measured for a variety of simple patterns. Generally, the spontaneous fixation tendencies hovered near the “center-of-gravity” of the pattern, providing that the overall dimensions of the figure were less than about 5 deg. “Open” figures such as angles were found to be roughly equivalent to their “enclosed” counterparts, such as triangles. The constraints imposed by the pattern upon the fixation tendencies occur at a level where the binocular inputs are processed. Of further importance was the fact that the fixation points approximate the foci observed in the same patterns when they are seen against a background of visual noise. It is suggested that the two results may be functionally related..     

Misspecification in Latent Change Score Models: Consequences for Parameter Estimation,Model Evaluation,and Predicting Change

Latent change score models (LCS) are conceptually powerful tools for analyzing longitudinal data (McArdle & Hamagami, 2001). However, applications of these models typically include constraints on key parameters over time. Although practically useful, strict invariance over time in these parameters is unlikely in real data. This study investigates the robustness of LCS when invariance over time is incorrectly imposed on key change-related parameters. Monte Carlo simulation methods were used to explore the impact of misspecification on parameter estimation, predicted trajectories of change, and model fit in the dual change score model, the foundational LCS. When constraints were incorrectly applied, several parameters, most notably the slope (i.e., constant change) factor mean and autoproportion coefficient, were severely and consistently biased, as were regression paths to the slope factor when external predictors of change were included. Standard fit indices indicated that the misspecified models fit well, partly because mean level trajectories over time were accurately captured. Loosening constraint improved the accuracy of parameter estimates, but estimates were more unstable, and models frequently failed to converge. Results suggest that potentially common sources of misspecification in LCS can produce distorted impressions of developmental processes, and that identifying and rectifying the situation is a challenge.     

Lack of free choice reveals the cost of multiple-target search within and across feature dimensions

Having to look for multiple targets typically results in switch costs. However, using a gaze-contingent eyetracking paradigm with multiple color-defined targets, we have recently shown that the emergence of switch costs depends on whether observers can choose a target or a target is being imposed upon them. Here, using a similar paradigm, we tested whether these findings generalize to the situation in which targets are specified across different feature dimensions. We instructed participants to simultaneously search for, and then fixate, either of two possible targets presented among distractors. The targets were defined as either two colors, two shapes, or one color and one shape. In one condition, only one of the two targets was available in each display, so that the choice was imposed. In the other condition, both targets would be present in each display, which gave observers free choice over what to search for. Consistent with our earlier findings, switch costs emerged when targets were imposed, whereas no switch costs emerged when target selection was free, irrespective of the dimension in which the targets were defined. The results are consistent with the operation of different modes of control in multiple-target search, with switch costs emerging whenever reactive control is required and being reduced or absent when displays allow for proactive control.     

Efficient Creativity: Constraint‐Guided Conceptual Combination

This paper describes a theory that explains both the creativity and the efficiency of people's conceptual combination. In the constraint theory, conceptual combination is controlled by three constraints of diagnosticity, plausibility, and informativeness. The constraints derive from the pragmatics of communication as applied to compound phrases. The creativity of combination arises because the constraints can be satisfied in many different ways. The constraint theory yields an algorithmic model of the efficiency of combination. The C³ model admits the full creativity of combination and yet efficiently settles on the best interpretation for a given phrase. The constraint theory explains many empirical regularities in conceptual combination, and makes various empirically verified predictions. In computer simulations of compound phrase interpretation, the C³ model has produced results in general agreement with people's responses to the same phrases.     

The Interaction of Criterion and Feedback Information in Learning a Drawing Task

Experiments were designed to examine the influence of criterion and feedback information in the learning of a two-dimensional drawing task. Experiment 1 showed that when the task criterion is well known to the subject, the combined presentation of criterion information and information feedback facilitates the rate of acquisition of the skill but not its overall performance level of achievement. Experiment 2 showed that when the task criterion information is not well known to the subject, presentation of criterion information facilitates both the rate of acquisition and the overall performance level and, furthermore, is essential if configuration information feedback is to be utilized effectively. Experiment 3 showed that it is the combined presentation of criterion and configuration information feedback, rather than the isolated presentation of either type of information alone, that facilitates learning and performance. Collectively, the findings from the three experiments suggest an interactive effect of prior knowledge by the learner and type of augmented information in facilitating the acquisition of skill, according to the constraints imposed in the task. The data are consistent with the proposal that the degrees of freedom in the information available to support motor skill learning must match the degrees of freedom to be constraint in the perceptual-motor workspace.     

The interaction of criterion and feedback information in learning a drawing task

Experiments were designed to examine the influence of criterion and feedback information in the learning of a two-dimensional drawing task. Experiment 1 showed that when the task criterion is well known to the subject, the combined presentation of criterion information and information feedback facilitates the rate of acquisition of the skill but not its overall performance level of achievement. Experiment 2 showed that when the task criterion information is not well known to the subject, presentation of criterion information facilitates both the rate of acquisition and the overall performance level and, furthermore, is essential if configuration information feedback is to be utilized effectively. Experiment 3 showed that it is the combined presentation of criterion and configuration information feedback rather than the isolate presentation of either type of information alone, that facilitates learning and performance. Collectively, the findings from the three experiments suggest an interactive effect of prior knowledge by the learner and type of augmented information in facilitating the acquisition of skill, according to the constraints imposed in the task. The data are consistent with the proposal that the degrees of freedom in the information available to support motor skill learning must match the degrees of freedom to be constraint in the perceptual-motor workspace.     

Visual discrimination thresholds for one- and two-dimensional Markov spatial constraints

Forced-choice discrimination thresholds were obtained for visual displays of a large number (1,000-3,600) of binary encoded elements with one- and two-dimensional Markov spatial constraints. Several factors which delimit such thresholds were explored. The primary determinant of sensitivity was the number of constrained elements within the display. Configurational features, such as the shape of the display have little influence on sensitivity. Thresholds for one-dimensional spatial constraints were consistently lower than for two-dimensional spatial constraints.     

Eye movements during search and detection in comparative visual search

Motivated by the fact that previous visual memory paradigms have imposed encoding and retrieval constraints, the present article presents two experiments that address how observers allocate eye movements in memory and comparison processes in the absence of constraints. A comparative visual search design (Pomplun, Sichelschmidt, et al., 2001) was utilized in which observers searched for a difference between two images presented side by side. Robust time course effects were obtained, whereby search was characterized by brief fixations and a high proportion of comparative saccades. Then, upon target detection, fixations were extended, more comparative saccades were elicited, and the search focus was narrowed. The saliency and presence of differences did not guide attention, and detection was contingent upon direct fixation of the targets. The results indicate that, when full control is given, observers adopt a strategy that cuts down on memory usage in favor of restricted encoding and active scanning.     

Bi-phasic hitting with constraints on impact velocity and temporal precision

The aim of the experiment was to investigate how bi-phasic hitting movements are organized to comply with both impact and temporal precision constraints. 'Bi-phasic' refers to a sequential movement with a preparatory movement away from the interception location followed by a strike phase. The interception location was fixed, as the motion of the hitting device was constrained to follow a straight path orthogonal to that of the approaching balls. We manipulated the required temporal precision by projecting balls with different constant approach speeds (1, 1.5, and 2m/s). Different impact constraints were imposed by instructing participants first to simply hit the ball and subsequently to hit the ball to a designated target area located either 55 or 105 cm away from the interception location. We determined several kinematic variables and used Principal Component Factor Analysis to classify these variables. The analysis revealed two independent factors: a 'velocity' factor (formed by impact velocity, peak velocity of the preparatory phase, peak velocity of the strike phase, and amplitude of the strike) and a 'timing' factor (formed by onset of the preparatory phase, moment of peak velocity of the preparatory phase, and onset of the strike phase). The 'velocity' factor scaled significantly with the required impact constraint and the 'timing' factor scaled significantly with ball speed.     

Effects of increased processing load on parallel processing of visual displays

Display elements were sequentially painted upon a display scope in regular and irregular spatial-temporal orders. The primary result of Mayzner, Tresselt, and their associates is confirmed: within specified temporal-spatial limits, display elements may be perceptually blanked. Characteristics of perceptually blanked elements can, however, be revealed by forced-choice testing. The accuracy of tilt discrimination for perceptually blanked elements is equal to, or better than, that for nonblanked elements. Perceptually blanked elements can also be distinguished from absent and from partially absent elements, presumably on the basis of a crude brightness discrimination. Sequential blanking effects as revealed in the accuracy of slant detection, are not critically dependent upon the magnitude of uniform spacing between the display elements.     

Postural stability and hand preference as constraints on one-handed catching performance in children

Effects of postural state and hand preference as constraints on 1-handed catching performance were investigated in different ability groups of children aged 9-10 years. On the basis of pretest data, the authors classified 48 participants into groups of good, intermediate, and poor catchers (n = 16 in each) and asked them to perform 1-handed catches with their preferred and nonpreferred hands while standing and sitting. The good catchers' performance was not affected by the imposed postural constraints but did improve when they used the preferred hand. A similar effect of hand preference was evident in the intermediate and poor catchers, but there was also an effect of postural constraint. Independent of hand preference, intermediate catchers' performance while seated improved significantly compared with that during standing. For poor catchers, there was an interaction between hand preference and posture; significant improvement was evident only when they used the preferred hand in the sitting condition. The finding that manipulation of posture and hand preference affected performance outcomes indicates that perceptual skill is not the only influence on catching performance in children. Manipulation of those key constraints may facilitate the acquisition of catching skill, but more research is needed to determine the permanence of those effects.     

Transfer effects as a function of sequential and quantitative schedule constraints

Schwartz (1982, 1988) found that a pretraining of contingent reinforcement interferes with subsequent rule discovery. The present study investigated the effects of schedule imposed sequential and quantitative constraints (Timberlake & Allison, 1974) on task performance in a subsequent test phase. Sixty-four Ss, students of the University of Duesseldorf, were assigned at random to one of four experimental conditions, differing according to the presence vs. absence of sequential and quantitative constraints, respectively. Discrimination-learning performance and variability during test phase were significantly better for Ss experiencing sequential constraint during treatment. In contrast, the introduction of a quantitative restriction during treatment had no statistically significant effects on test phase performance.