Effects of route guidance variable message signs (VMS) on driver behaviour

Effects of route guidance Variable Message Signs (VMS) on speed and route choice were investigated in a field study on two sites on motorways. Two VMS were used in the study, which displayed information about a closed road section downstream on the motorways and recommendations for alternative routes. Route choice, speed and braking behaviour were compared between vehicles approaching the VMS while they displayed messages and while they were left blank without message. There was high compliance with the messages on the VMS. About every fifth vehicle changed route choice according to the recommendation, and almost none drove as far as the closed road section. Speed measurements of 3342 vehicles showed large speed reductions, and video observations showed that large proportions of vehicles braked while approaching the VMS. The speed reductions and braking manoeuvres can partly be attributed to attention overload or distraction due to the information on the VMS. However, a proportion of the speed reductions was due to chain reactions where one vehicle braked and forced the following vehicles to brake or change lanes in order to avoid collisions. Safety problems may result directly from distraction, or indirectly from the reactions of the drivers to the distraction.     

On the optimality of serial and parallel processing in the psychological refractory period paradigm: Effects of the distribution of stimulus onset asynchronies

Within the context of the psychological refractory period (PRP) paradigm, we developed a general theoretical framework for deciding when it is more efficient to process two tasks in serial and when it is more efficient to process them in parallel. This analysis suggests that a serial mode is more efficient than a parallel mode under a wide variety of conditions and thereby suggests that ubiquitous evidence of serial processing in PRP tasks could result from performance optimization rather than from a structural bottleneck. The analysis further suggests that the experimenter-selected distribution of stimulus onset asynchronies (SOAs) influences the relative efficiency of the serial and parallel modes, with a preponderance of short SOAs favoring a parallel mode. Experiments varying the distribution of SOAs were conducted, and the results suggest that there is a shift from a more serial mode to a more parallel mode as the likelihood of short SOAs increases.     

Perceptual learning in auditory temporal discrimination: No evidence for a cross-modal transfer to the visual modality

Perceptual learning was used to study potential transfer effects in a duration discrimination task. Subjects were trained to discriminate between two empty temporal intervals marked with auditory beeps, using a twoalternative forced choice paradigm. The major goal was to examine whether perceptual learning would generalize to empty intervals that have the same duration but are marked by visual flashes. The experiment also included longer intervals marked with auditory beeps and filled auditory intervals of the same duration as the trained interval, in order to examine whether perceptual learning would generalize to these conditions within the same sensory modality. In contrast to previous findings showing a transfer from the haptic to the auditory modality, the present results do not indicate a transfer from the auditory to the visual modality; but they do show transfers within the auditory modality.     

How well do ratings of academic performance by mothers and their sons correspond to grades,achievement test scores,and teachers' ratings?

Accurate perceptions of their child's academic performance are pivotal for parents' encouragement of their child's academic efforts. In research studies, parents' reports of their child's academic achievement, as well as the child's own reports, are often used as a proxy for teachers' ratings or grades. However, are parents' reports or their child's reports accurate and unbiased? We investigated whether ratings of academic performance made by mothers and their sons corresponded more closely to final grades and achievement test scores than did similar ratings made by teachers for three large samples of boys. Mothers' ratings correlated with final grades as well or better than teachers' ratings but more poorly with achievement test scores than did teachers' ratings. The seventh-grade boys' ratings correlated more poorly with both final grades and achievement test scores than did teachers' or mothers' ratings. Across all three samples combined, mothers were more likely to over-estimate rather than under-estimate the final grade. The same was true of the seventh grade sample of boys. Once the effect of final grade had been controlled, little evidence of a consistent pattern of associations between maternal demographic, parenting, and child behavior variables and either over- or underestimation was found.     

Response force is sensitive to the temporal uncertainty of response stimuli

Three experiments examined whether temporal uncertainty about the delivery of a response stimulus affects response force in a simple reaction time (RT) situation. All experiments manipulated the foreperiod; that is, the interval between a warning signal and the response stimulus. In the constant condition, foreperiod length was kept constant over a block of trials but changed from block to block. In the variable condition, foreperiod length varied randomly from trial to trial. A visual warning and response stimulus were used in Experiment 1; response force decreased with foreperiod length in the variable condition, but increased in the constant condition. This result is consistent with the hypothesis that responses are less forceful when the temporal occurrence of the response stimulus is predictable. In a second experiment with an auditory warning signal and a response stimulus, response force was less sensitive to foreperiod manipulations. The third experiment manipulated both the modality and the intensity of the response signal and employed a tactile warning signal. This experiment indicated that neither the modality nor the intensity of the response signal affects the relation between response force and foreperiod length. An extension of Näätänen’s (1971) motor-readiness model accounts for the main results.     

The relaxation word of the day: A simple technique to measure adherence to relaxation

A new procedure of assessing adherence to home practice of relaxation is presented. The technique involved the subject identifying one of four possible relaxation words of the day at the end of a taped relaxation session. The method was employed to assess the relationship between adherence to relaxation and decline of blood pressure during a 10-session/8-week relaxation program involving 17 hypertensive subjects. No statistically significant relationship was found on either a short-term or a long-term basis. An advantage of the assessment technique is that it appears easily integrated into the overall therapeutic objective for relaxation therapy; a disadvantage is that the subject needs to comply not only with the relaxation schedule but also with the monitoring procedure.This research study was funded by NIH Grant HL27159.     

Attitudes toward the childless spouse

Two studies assess attitudes toward the childless life-style. One study uses an unstructured response style in order to determine the motivation for and effects of the decision attributed to the person intending to be childless. The second study assesses the relationship between self-reported attitudes measures. The studies suggest the person selecting the childless life-style may be viewed by others as less well adjusted or misguided in this choice, which is inconsistent with the majority of published data on the childless spouse.