Influence of different modes of real time visual information on single aimed movements

This study shows that the difference in appearance between two types of computer generated real time visual information namely, cursor and trace feedback, becomes visible in the execution of aimed stylus movements. Movement execution was scrutinized by division into four relevant subsequent constituents on the basis of key kinematic events. As expected, the final section of a movement took more time and showed a larger number of adjustments in the cursor condition. Instead, the influence of trace feedback on movement execution became discernible in earlier sections of movement execution. When a combination of feedback types was employed, trace feedback seemed to dominate the impact on execution. Discussion focuses on the contribution of the present study to understanding the impact of specific features inherent to types of real time visual feedback, and the relevance of the present study's result to future research.     

Large-scale visual frontoparallels under full-cue conditions

We determined the curvature of apparent frontoparallels in a natural scene (a large lawn in broad daylight). Data on frontoparallels in these conditions are very sparse and reveal idiosyncratic curvatures of frontoparallels and irregular variation with distance. We used a method of bisection of linear segments indicated through pairs of stakes at angular separations (from the vantage point) of up to 120 deg. Distances of 2 m and 10 m (in the forward direction) were used. The bisection was carried out by the observer through maneuvering a radio-controlled vehicle carrying a third stake. Four observers participated in the experiment; they had no problems with the task and yielded mutually consistent results. We found that the frontoparallels are significantly curved and are concave towards the observer. Surprisingly, the sign of the curvature is opposite to that found when the frontoparallels are defined through an exocentric pointing task. Available theory (Luneburg's) does not predict this, but the theory is hardly applicable to the case of vision in natural scenes. This interesting discrepancy has not been reported before.     

Effects of motor programming on the power spectral density function of finger and wrist movements

Power spectral density analysis was applied to the frequency content of the acceleration signal of pen movements in line drawing. The relative power in frequency bands between 1 and 32 Hz was measured as a function of motoric and anatomic task demands. Results showed a decrease of power at the lower frequencies (1-4 Hz) of the spectrum and an increase in the middle (9-12 Hz), with increasing motor demands. These findings evidence the inhibition of visual control and the disinhibition of physiological tremor under conditions of increased programming demands. Adductive movements displayed less power than abductive movements in the lower end of the spectrum, with a simultaneous increase at the higher frequencies. The relevance of the method for the measurement of neuromotor noise as a possible origin of delays in motor behavior is discussed.     

The role of vision in the temporal and spatial control of handwriting.

The general observation that handwriting is not noticeably impaired by the withdrawal of vision can be explained in two ways. One might argue that vision is not needed during the act of writing. Micro-analyses should then reveal that spatial as well as temporal writing features are identical in conditions of vision and no vision. Alternatively, it is possible that vision is needed during the act of writing, but that without vision possible errors and inaccuracies have to be prevented. Assuming that the latter would place an extra demand on movement control, this should be revealed by an increase in processing time. We have found evidence for the latter view in the present study in which 12 subjects wrote a nonsense letter sequence with and without vision. Close examination showed that writing shapes remained equally invariant under both vision conditions, suggesting that spatial control was unaffected by withdrawing vision. The prediction that invariance of shapes is preserved in the absence of vision at the expense of processing time increments was confirmed. The increase of reaction time observed when visual guidance was withdrawn suggests that more processing time was needed prior to the movement start. Moreover, the RT increment was larger when a short writing duration was instructed. The present findings will be discussed in light of the remarkable flexibility of writing as a motor skill in which writers appear to be able to employ specific strategies to preserve shape in the absence of visual guidance.     

Creating ‘Local Publics’: Responsibility and Involvement in Decision-Making on Technologies with Local Impacts

Science and Engineering Ethics - This paper makes a conceptual inquiry into the notion of ‘publics’, and forwards an understanding of this notion that allows more responsible forms of...     

Perception of illuminance flow in the case of anisotropic rough surfaces

Human observers estimate the illumination direction of rough surfaces rather precisely. When surfaces are rough, the illumination generates visible "texture" from differential shading at the level of the roughness, whereas differential illumination at the level of significant global surface curvature leads to the more familiar "shading". The shading is used in conventional shape-from-shading (SFS) algorithms, which ignore the illumination texture cue. Because of this simplification, SFS algorithms are typically formulated as global problems (partial differential equations, etc.). Human observers are likely to apply different methods than do these conventional SFS algorithms, however. When the roughness is not isotropic, one expects systematic errors in the visual detection of illumination direction, conceivably giving rise to erroneous shape estimates. Here we addressed this issue through systematic psychophysics on illumination direction detection as a function of the roughness anisotropy. Our expectations were fully borne out, in that the observers committed the predicted systematic errors. These results are precise enough to allow the inference that illumination direction detection is based on second-order statistics--that is, of edge detector (rather than line detector) activity.     

Introduction to the Symposium on Sabine Roeser’s Risk,Technology, and Moral Emotions

Science and Engineering Ethics -     

Longitudinal transmission of conflict resolution styles from marital relationships to adolescent-parent relationships.

This study longitudinally investigated transmission: Can the way adolescents resolve conflicts with their parents be explained by the way parents resolve conflicts with each other? Questionnaires about conflict resolution styles were completed by 282 young adolescents (mean age = 13.2) and their parents. Path analyses with cross-lagged effects indicated that transmission of conflict resolution styles from marital relationships to adolescent-parent relationships occurs: Conflict engagement and positive problem solving in marital relationships were significantly related to, respectively, conflict engagement and positive problem solving in adolescent-parent relationships 2 years later. No significant longitudinal effects emerged with regard to withdrawal. Thus, the study shows that the way marital conflicts are handled affects how adolescents deal with conflicts.     

Pointing out of the picture

The eyes of portrayed people are often noticed to 'follow you' when you move with respect to a flat painting or photograph. We investigated this well-known effect through extensive measurements of pictorial relief and apparent orientation of the picture surface for a number of viewing conditions, including frontal and oblique views. We conclude that cases of both oblique and frontal viewing are very similar in that perception simply follows what is indicated by the proximal stimulus, even though this may imply that the (perceived) physical and pictorial spaces segregate. The effect of foreshortening then causes an apparent narrowing of pictorial objects. We find no evidence for any 'correction' mechanisms that might be specifically active in oblique viewing conditions.