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The hypothesis was tested that the decline of apparent size with elevated gaze results from a latent tendency of the eyes to diverge and thus increased vergence effort. Through the use of a method of category estimation, the decline of apparent size on elevation or depression of gaze was found not to be different between subjects with larger or smaller changes of dark vergence and thus vergence effort. In a 2nd experiment, vergence effort was varied by varying gaze elevation and the angle of convergence. With vergence effort constant, apparent size was dependent on the angle of convergence rather than being constant. It is concluded that apparent size does not depend on vergence effort and that the effect of gaze elevation on apparent size cannot be attributed to its concomitant effect on dark vergence.

Temporal and spatial movement characteristics are often seen as controlled separately, although they are not independent. Even in the case of simple oscillations mean frequency and mean amplitude covary when one or the other is changed intentionally. The present experiment revealed that in rapid finger oscillations there is also a cycle-to-cycle covariation so that smaller amplitudes are associated with locally increased frequency and (the associated) earlier electromyographic (EMG) bursts. Both globally and locally the observed covariations are consistent with modeling rhythmic movements as output of a driven damped oscillator. The existence of local spatio-temporal covariations suggests limitations for models of timing and reasons for the observation that spatio-temporal movement characteristics cannot be chosen arbitrarily even in uniarticuiar movements. [ABSTRACT FROM AUTHOR]

We examined age-related changes of executive functions by means of random noun generation. Consistent with previous observations on random letter generation, older participants produced more prepotent responses than younger ones. In the case of random noun generation, prepotent responses are nouns of the same category as the preceding noun. In contrast to previous observations, older participants exhibited stronger repetition avoidance and a stronger tendency toward local evenness-that is, toward equal frequencies of the alternative responses even in short subsequences. These data suggest that at higher adult age inhibition of prepotent responses is impaired. In addition, strategic attentional processes of response selection are strengthened, in particular the application of a heuristic for randomness. In this sense response selection is more controlled in older than in younger adults.

An attempt made to re-analyse tracking data of a cosmonaut to determine whether the tracking movements reveal the same kind of microgravity effects on motor control as were apparent in rapid aiming movements performed with the same hardware by the same cosmonaut is presented.

Concurrent movements of different effectors are subject to structural constraints that facilitate certain patterns of coordination but impede others. The constraints for concurrent rotations of the head and a bimanually operated steering device were explored in two experiments. To indicate structural constraints, the difference between concurrent periodic rotations in same and different directions with respect to the variable error of synchronization was used. The first experiment showed less error for rotations in same directions than for rotations in opposite directions. In the second experiment, the same result was obtained with a horizontal and a backward-tilted steering wheel. Adding gaze shifts to head oscillations increased the accuracy of synchronization but did not affect the difference between both coordination patterns. In contrast to the synchronization of head and steering device, the variable error of synchronization of gaze and steering wheel did not differ between both modes of coordination; the error was again reduced when head oscillations were added to the saccades between eccentric fixation targets. This suggests space related (or allocentric) constraints, which most likely originate from concurrent specifications of movement directions in coupled spatiotopic maps so that the specification of rotations in the same direction is facilitated in comparison to rotations in opposite directions. [ABSTRACT FROM AUTHOR]

An interpretation of John Annett's theory of subjective rating scales is given. It is argued that his arguments is true for the myriad of measurements taken by the sensory receptors humans are equipped with.

ABSTRACT. The authors examined the hypothesis that the phasic and the static cross-talk effects found in bimanual movements with different target amplitudes originate at different functional levels of motor control, [...]

In a series of 4 experiments, the authors examined involuntary rotations of a steering device (handlebar or wheel) that were associated with periodic head rotations and eccentric head positions. Periodic [...]