External memory: High speed,low speed,and no speed

This paper describes potential constraints on the selection of external memory devices (stimulus sources) and suggests options available to the would-be user of such systems for estimating research requirements and the functional parameters of the available external memory devices.     

The effect of speed limit credibility on drivers' speed choice

Credibility of speed limits is a key factor affecting drivers’ compliance with speed limits. Two experiments were conducted to investigate how credibility of speed limits affects judgments of appropriate speed. The first experiment aimed to establish speeds deemed appropriate by investigating Malaysians drivers’ judgments of the appropriate speed to drive based on photographs of roads with the speed limit sign erased. Drivers chose speeds which correlated with but were higher than the actual speed limits of the roads. Analysis of road characteristics suggested they based their decisions mainly on features of the road itself rather than of the roadside. The second experiment tested the impact of credibility of speed limit information on the speed drivers judged appropriate. Drivers judged the appropriate speed to drive for the same photographs as in Experiment 1 with speed limit information provided. Four conditions were included: two conditions where the speed limit posted was 10% higher or 10% lower than the appropriate speed established in Experiment 1 (credible speed limits), and two conditions where the posted speed limit was 50% higher or 50% lower than the appropriate speed (non-credible speed limits). Posted speed limits did affect drivers’ judgments about the appropriate speed to drive. Credibility also influenced judgments whereby drivers selected appropriate speeds consistent with the speed limits for the 10% lower condition, but not for speed limits that deviated highly from the appropriate speed judged in Experiment 1.     

Effects of speed feedback signs and law enforcement on driver speed

This study analyzes the effects of implementing three speed management strategies, namely speed feedback signs, periodic law enforcement, and speed feedback sign supported with periodic law enforcement on driver speed behavior and compliance. To analyze the effectiveness of each strategy, nine locations in Pima County, Arizona, were studied in a cross-sectional framework. For each study site, the driver’s speed, date, time, and vehicle’s length were collected at a location prior to the speed management zone as the baseline, at the speed management zone, and downstream of the speed management zone. The general effect showed that all the strategies were effective in reducing average speed and the proportion of drivers exceeding the speed limit. In addition, the results of the robust heteroscedastic ANOVA test showed that among all the strategies, the speed feedback sign supported with periodic law enforcement was the most effective one. Moreover, it was shown that by supporting the speed feedback sign with periodic law enforcement, the reduction in average speed and proportion of drivers exceeding the speed limit would last, even after passing the speed management strategy. In other words, the existence of periodic law enforcement could potentially modify drivers’ behaviors and increase the spatial effectiveness of speed feedback signs. Comparing the behavior of truck and passenger car drivers also revealed similar results. That is, both truck and passenger car drivers tend to slow down after observing the speed management strategy. The experimental evidence indicates positive benefits for reducing excessive speeding behaviors at the sites.     

Effects of reduced threshold of automated speed enforcement on speed and safety

This study was designed to evaluate the effects of a reduced threshold of the fixed automated speed enforcement system on speed and safety on a two-lane rural road. The threshold was lowered from 20 km/h to 4 km/h and the public was informed about the change. Driving speeds on the experimental and control road before and after the change were compared. The main results showed that the reduced threshold decreased the mean speed by 2.5 km/h, the standard deviation of speed by 1.1 km/h and the proportion of exceeding vehicles by 11.8 percentage units. In conclusion, lowering the threshold of automated speed enforcement combined with an appropriate information campaign bring about a significant speed reduction that could contribute to substantial safety benefits.     

On visual speed

Summary According toJ. F. Brown the dependence of visual speed on field factors is principally due to influences which such field factors exert on phenomenal time.K. Koffka has pointed out that the same dependence may be due to variations of the spatial threshold in fields of different properties. In this paper experiments have been reported which in two cases decide in favor ofKoffka's explanation. This explanation is likely to be applicable to further instances. — Some ofBrown's own experimental results appear to be incompatible with his theory.

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Zusammenfassung J. F. Brown erkl?rt die Abh?ngigkeit gesehener Geschwindigkeiten von Feldfaktoren durch entsprechende Variationen im Gebiet der ph?nomenalen Zeit.K. Koffka hat darauf aufmerksam gemacht, da? die gleichen Tatbest?nde auf Abh?ngigkeit der Raumschwelle von Feldfaktoren beruhen k?nnten. Die vorliegende Arbeit berichtet über Versuche, die in zwei F?llen zugungsten vonKoffkas Erkl?rung entscheiden. Wahrscheinlich kann diese Erkl?rung auf andere F?lle ausgedehnt werden. —Brown selbst hat Versuche angestellt, deren Ausfall mit seiner Theorie unvereinbar erscheint.

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This investigation was performed under the direction of ProfessorW. K?hler. The author is indebted to him for the formulation of the problem, to him and to Dr.H. Wallach for guidance in the interpretation and presentation of the results, and to ProfessorJ. F. Brown for his courtesy in placing at his disposal published and unpublished papers.     

Effect of movement speed on lower and upper body biomechanics during sit-to-stand-to-sit transfers: Self-selected speed vs. fast imposed speed

Preferred and fast speed sit-to-stand and stand-to-sit (STS) tests are prevalent in literature, but biomechanical changes between the different speeds of STS have never been studied. Understanding differences between these STS techniques will better inform experimental design for research assessing functional ability in clinical populations. The purpose of this study was to investigate the effect of different speeds of STS transfers on lower body and trunk kinematics and kinetics in healthy adults. Nineteen healthy middle-aged and older adults participated in this study. Two different speeds of STS were tested: self-selected speed and fast speed (as quickly as possible). Ten Vicon cameras and two AMTI force platforms were used to collect three-dimensional kinematic and kinetic data. During sit-to-stand transfer, peak knee extension velocity and knee extension moment were significantly increased for the fast speed STS as compared to the preferred speed STS. During stand-to-sit transfer, peak knee extension moment and lower back moment were significantly increased while STS time was decreased for the fast speed STS as compared to the preferred speed STS. Our results indicate that the fast speed STS could be more challenging for participants compared to the preferred speed STS evidenced by greater knee and lower back joint movements. Therefore, fast STS tests should be reconsidered when testing middle-aged and older adults with chronic low back pain and knee joint problems.     

Understanding how speed affects performance of polyrhythms: transferring control as speed increases

Pianists (N = 9) memorized and performed polyrhythms over a range of speeds from 1 to 16 notes/s. Using several fingers of each hand to press the keys on a piano keyboard, they performed the 5:3 polyrhythm by playing "3s" with one hand simultaneously with "5s" in the other. All the participants were able to maintain overall tempos and rhythms to within 10% of target speeds despite increasing difficulty. Increasing speed led to a transfer of control at about 6 notes/s, with a modular system operating above that speed. The participants were also able to engage in timing coupling at all speeds, even when the hands belonged to different people.     

Limiting speed,towards an intelligent speed adapter (ISA)

This study concerns the effects of a prototype intelligent speed adapter (ISA) on speeding in actual traffic. Twenty-four subjects were included in a test of effects of feedback on speed behaviour, mental workload and acceptance. Subjects drove an instrumented vehicle in normal traffic on various types of roads with different speed restrictions. Subjects completed the test route twice, half of the subjects received specific feedback in the second trial (experimental group), half of the subjects did not (control group). The groups differed in several ways, the most important being adaptation of their behaviour after feedback. Subjects in the experimental group behaved more according to traffic rules, in particular speed limits, than subjects in the control group. No significant differences in workload were found. Two types of feedback were tested to acceptance and were rated differently.     

The speed of free will

Do voluntary and task-driven shifts of attention have the same time course? In order to measure the time needed to voluntarily shift attention, we devised several novel visual search tasks that elicited multiple sequential attentional shifts. Participants could only respond correctly if they attended to the right place at the right time. In control conditions, search tasks were similar but participants were not required to shift attention in any order. Across five experiments, voluntary shifts of attention required 200–300 ms. Control conditions yielded estimates of 35–100 ms for task-driven shifts. We suggest that the slower speed of voluntary shifts reflects the “clock speed of free will”. Wishing to attend to something takes more time than shifting attention in response to sensory input.     

Predictors of picture naming speed

We report the results of a large-scale picture naming experiment in which we evaluated the potential contribution of nine theoretically relevant factors to naming latencies. The experiment included a large number of items and a large sample of participants. In order to make this experiment as similar as possile to classic picture naming experiments, participants were familiarizedwith the materials during a training session. Speeded naming latencies were determined by a software key on the basis of the digital recording of the responses. The effects of various variables on these latencies were assessed with multiple regression techniques, using a repeated measures design. The interpretation of the observed effects is discussed in relation to previous studies and current views on lexical access during speech production.     

Coherence determines speed discrimination

The visual system must determine which elements in a scene to regard as parts of a single object and which to regard as different objects. We can create stimuli that are ambiguous, ie consistent with more than one interpretation, and ask in what situations the stimulus elements are interpreted as part of a single object and when they are interpreted as multiple objects. The ambiguous stimuli in this study were moving plaid patterns--the sum of two drifting gratings with different orientations. Observers may see a rigid coherent plaid object moving in one direction, or may see two gratings moving in different directions sliding over one another. When the gratings have similar contrasts they appear to cohere and only the plaid speed is perceptually available; when the gratings have different contrasts they appear to slide and only the speeds of the gratings are perceived. Coherence thus determines what speed information is passed to higher stages of motion processing. A two-stage model of plaid motion perception is presented which agrees with the model proposed by Adelson and Movshon and extends it, detailing the relationship between coherence and speed discrimination.     

Effects of speed display signs on driving speed at pedestrian crossings on collector streets

This study was designed to evaluate the short- and long-term effects of speed display signs on driving speed at pedestrian crossings in a low-speed (40 km/h) urban environment. Driving speeds were compared 1 week before installation, after installation (1 week; 1 month; 3 months; 5 months) and 1 week after removal. The main results showed that the speed displays decreased the mean speed by 0.5–2.9 km/h, which translates to a 4–22% drop in pedestrian fatality risk. Furthermore, there was a drop in the proportion of speeding vehicles and approaching speed of individual vehicles. The decrease in speed persisted over time, suggesting that speed displays may reduce speeds in the long term. In conclusion, installing speed displays at pedestrian crossings on collector streets reduces driving speeds and could contribute to the safety of pedestrians.     

Movement speed in children

Two experiments were conducted to investigate movement speed in children of 6, 8, 10, and 12 yr of age. Different information loads were presented to the children on a serial task (Experiment 1), and on a discrete task (Experiment 2). On both tasks there was a linear relationship between movement time and information load. Reaction time was relatively unaffected by and increase in the difficulty of the required movement. By employing the formula, capacity = (Index of Difficulty) / (movement time), there was an increase in capacity by age with very little overlap between the ages. Strategies on the serial task were discussed and comparisons with adult subjects were made.     

Subitizing speed,subitizing range,counting speed,the Stroop effect,and aging: capacity differences and speed equivalence

Thirty younger and 29 older adults were tested on reaction times for set size of a display of 1 to 9 digits. On half of the trials, the nominal value of the digits was equal to the size of the set displayed; on the other half, the value differed by 1 from the set size (Stroop interference). We found evidence for age differences in subitizing span (2.83 vs. 2.07). Once individual differences in subitizing range were taken into account, no age differences were found in the rate of either subitizing or counting, and no individual differences were apparent in subitizing speed. There was no age difference in the susceptibility to the Stroop effect. The results suggest that, with advancing age, the size of the focus of attention may shrink, but speed of access to elements in the focus of attention may remain constant.     

Guiding drivers towards safer driving speed: Exploiting visual dominance in speed adaptation

Inappropriate speed is a main cause of accidents. Drivers are often unaware of potential risks due to inadequate speed. To prevent dangerous situations, we need to understand perceptual factors influencing human speed perception. Due to the prominent role of vision in driving, we examined the effect of visuo-spatial stimuli on speed based on the optic flow. While developing an adaptive infrastructure measure to reduce speed, we conducted two consecutive studies, a driving simulator study and a field test to investigate findings further. In both studies, we placed lights on two sides of a highway exit and either illuminated them statically or activated them in a way that they appeared to be moving towards the driver. We expected drivers to slow down more when seeing static light stimuli compared to a baseline without lights. We also expected drivers to decrease speed more in conditions with oncoming lights compared to a baseline, and to static lights, due to distorted speed perception. The first study in a static driving simulator revealed no difference between conditions. In the field test, both static lights and lights moving towards the driver led to a speed reduction compared to a baseline but did not differ from one another. Lights in general led to lower driving speed, potentially due to their warning character, but we found no difference between the light conditions, suggesting that the effect might not be based on the optic flow. Future research should investigate the relationship between driven and perceived speed more closely.     

Aging and the perception of speed

Two experiments were conducted to explore the potential effects of aging upon the perception and discrimination of speed. In the first experiment, speed difference thresholds were obtained for younger and older observers for a variety of standard speeds ranging from slow to fast. The second experiment was designed to evaluate the observers' ability to discriminate differences in the speed of moving patterns in the presence of significant amounts of noise (the noise was manipulated by limiting the lifetimes of individual moving stimulus elements). The results of both experiments revealed a significant deterioration in the ability of the older observers to perceive or detect differences in speed. While the presence of noise was found to affect the observers' discrimination performance, it affected both younger and older observers' thresholds in a proportionally equivalent manner-the older observers were no more affected by noise than the younger observers.     

Predictors of picture naming speed.

We report the results of a large-scale picture naming experiment in which we evaluated the potential contribution of nine theoretically relevant factors to naming latencies. The experiment included a large number of items and a large sample of participants. In order to make this experiment as similar as possible to classic picture naming experiments, participants were familiarized with the materials during a training session. Speeded naming latencies were determined by a software key on the basis of the digital recording of the responses. The effects of various variables on these latencies were assessed with multiple regression techniques, using a repeated measures design. The interpretation of the observed effects is discussed in relation to previous studies and current views on lexical access during speech production.     

The speed of individual face categorization

How fast does the human visual system discriminate individual faces? To address this question, we used a continuous-stimulation paradigm in which event-related potentials (ERPs) to a face stimulus are recorded with respect to another face stimulus, rather than to a preceding blank-screen baseline epoch. Following the shift between two face stimuli, posterior sites showed an early negative ERP deflection that started at 130 ms and peaked at 160 ms, the latency of the N170, an ERP component associated with discriminating faces from objects. The ERP we recorded was larger in amplitude when the preceding stimulus was perceived as a different individual face rather than the same individual face, although face pairs were of equal physical distance in the two conditions. These findings provide direct evidence that individual face discrimination in humans can take place as early as 130 ms following stimulus onset, during the same time window as face detection.     

Aging and the speed of time

Correlational and experimental methods provide evidence relevant to seven theories of humans’ general impressions of the speed of time, including theories of the purported subjective acceleration of time with aging. A total of 1865 adults from two countries, ranging in age from 16 to 80, reported how fast time appears to pass over different spans of time. Other measures tapped the experience of life changes and time pressure, and experimental manipulations were used to test two models based on forward telescoping and difficulty of recall. Respondents of all ages reported that time seems to pass quickly. In contrast to widely held beliefs, age differences in reports of the subjective speed of time were very small, except for the question about how fast the last 10 years had passed. Findings support a theory based on the experience of time pressure.