Fast aiming movements with the left and right arm: Evidence for two-process theories of motor control

Summary The kinematics of leftward and rightward movements are different. The question is raised whether these differences in both arms are best accounted for in terms of the flexion-extension dimension or the leftward-rightward dimension. In a simple step-tracking experiment the acceleration-time curves of fast flexions and extensions of the left and of the right elbow joint in a horizontal plane were recorded. The durations of individual segments of the acceleration curves are best predicted by spatial direction: that is, the differences between leftward and rightward movements are either both positive or both negative in both arms. This holds only for the first part of the movement until maximum deceleration is reached. From then on the timing is best predicted by the flexion-extension dimension. This is taken as evidence for a two-process theory of motor control according to which a central process is first in command and a lower-level, muscle-related process then takes over. Although a change which corresponds to the one observed in the time variables is not seen in the maxima of the acceleration curves, this seeming disparity can be reconciled with a two-process theory.     

Work Values of School Counselors Attending NDEA Summer Guidance Institutes

The work values of 164 men and 108 women school counselors, experienced and qualified, and enrolled in advanced summer guidance institutes, were studied by means of the Work Values Inventory. Sex, institutional, and occupational comparisons were made. Women counselors stress esthetic, intellectual, and way-of-life values more than men counselors, who put more emphasis on economic returns, managing, and surroundings. In comparison with other occupational groups studied, men counselors stress economic returns, security, and prestige, and attach less importance to esthetics, creativity, and intellectual stimulation.     

Some properties of the olfactory system of man

Preliminary investigations into the effects of a 12-h diurnal variation suggested there was a 10-fold decrease in odor sensitivity from morning to evening. For a selected group of odorants (methyl, t-butyl, and phenyl isonitrile), the difference between detection and recognition thresholds in general was found to be 10-fold; however, for some Ss the difference was less. When Ss were blindfolded, no changes in odor sensitivity were noted. Similarly, imposing an auditory stress on the test situation did not significantly alter odor sensitivity in either experienced or naive Ss,     

Olfactory detection thresholds in man under conditions of rest and exercise

Detection thresholds for seilen odorants were measured under conditions of rest and exercise. The test panel comprised six males with previous experience in odor detection. Exercise was maintained constant by using a modified bicycle positioned within the context of an air-dilution olfactometer. The effects of exercise were idiosyncratic for Ss: odor sensitivity was increased in some Ss, decreased in some, and not changed in others. Results of these experiments are discussed in terms of intra-subject variance within sessions and from session to session. In addition, two test techniques—one a fixed series and the other a tracking procedure—were evaluated for rapid estimation of an odor threshold. The tracking procedure facilitated prompt detection of changes in sensitivity for individual Ss.     

The physical factor structure of random forms and their judged complexity1

This study relates the perceived complexity of 2fl random forms to their physical factor structure. Ten principal axes, accounting for 94 per cent of the total variance of 24 physical measures, were rotated using the Varimax criterion. Factor scores for each form were correlated with the complexity ratings of the forms by each of 11 Ss. A single factor accounted for most of the variance in the complexity ratings. This factor was best described by four physical measures: the number of turns in the form, the length of the perimeter, the perimeter squared to area ratio, and the variance of the internal angles of the form.     

Choice reaction and unequal stimulus frequencies in an absolute judgment situation

Previous investigators have reported discrepant results for Ss in a choice reaction time (CRT) situation when stimuli are not equi-probable. Sixty Ss participated in an absolute judgment CRT task under three conditions of equi-probable stimuli and three of unequally probable stimuli. The results indicate that previous findings may be determined by a threshold dependent upon the effect of unequal stimulus frequencies and the utilities of different response strategies.     

The physical factor structure of random forms and their judged complexity

This study relates the perceived complexity of 20 random forms to their physical factor structure. Ten principal axes, accounting for 94 per cent of the total variance of 24 physical measures, were rotated using the Varimax criterion. Factor scores for each form were correlated with the complexity ratings of the forms by each of 11 Ss. A single factor accounted for most of the variance in the complexity ratings. This factor was best described by four physical measures: the number of turns in the form, the length of the perimeter, the perimeter squared to area ratio, and the variance of the internal angles of the form.     

Position reversal training in the virginia opossum: Evidence for the acquisition of a learning set

To obtain an estimate of the learning ability of opossums, five tame ones were trained on a series of position reversals to a criterion. With 4 trials per day there was no consistent improvement over a series of 15 reversals. When each daily session was increased to as many trials as needed to reach criterion, errors dropped sharply, indicating the formation of a position learning set. Upon return to 4 trials per day, 3 of 4 animals continued to perform with few errors, showing transfer of learning set. Opossums do more poorly than rats on this task, which is in agreement with the relative phyletic level of the two species.