The effects of vehicle color and travel direction on perceived speed error varies by judgment type among older pedestrians.

OBJECTIVE: Misjudgments of vehicle speed or distance frequently lead to collisions, particularly among older pedestrians who are less accurate in estimating vehicle speeds than younger individuals. However, comprehensive studies that assess multiple factors influencing speed perception in older pedestrians are lacking. METHODS: This research utilized computer simulations to explore how vehicle color (red, green, blue) and direction of travel (approaching or receding) affect perceived speed errors in both relative and absolute judgment scenarios among older pedestrians. RESULTS: Data from 38 older adults and 40 college students indicated that red vehicles were associated with fewer perceived speed errors than either green or blue vehicles. Errors increased for vehicles moving away, with absolute judgments showing greater discrepancies than relative ones. Analysis revealed that, across various combinations of the three independent variables-vehicle color, vehicle direction, and judgment type-the older participants exhibited significantly larger perceived speed errors compared to college students. Furthermore, the study identified significant interactions between vehicle color and direction, and between judgment type and vehicle direction. CONCLUSION: Our findings are beneficial in understanding the factors influencing older pedestrians' speed perceptions, aiding public safety and informing car design to ensure safer roads for older pedestrians.

Investigating the influence of visuospatial stimuli on driver's speed perception: a laboratory study.

Driving at an inappropriate speed is a major accident cause in the EU. Understanding the underlying sensory mechanisms can help to reduce speed and increase traffic safety. The present study investigated the effect of visuospatial stimuli on speed perception using an adaptive countermeasure to speeding based on a manipulation of optic flow. We added red lights on both sides of a simulated road. We expected speed to be perceived as faster when lights moved toward drivers due to increased optic flow, whereas we expected static light stimuli to not alter the optic flow and thus not influence speed perception. Two experiments applied the method of constant stimuli. To this end, participants encountered several trials of two video sequences on a straight road. A reference sequence showed the same traveling speed while test sequences varied around different traveling speeds. Participants indicated which sequence they perceived as faster, leading to the calculation of the point of subjective equality (PSE). A lower PSE indicates that the speed in this experimental condition is perceived as faster than in another experimental condition. Experiment 1A did not show a difference between PSEs of static and oncoming lights. Because participants had counted reflector posts for speed estimation, we removed these reflector posts in Experiment 1B and found a lower PSE for oncoming lights. Thus, such light stimuli may have an effect only in situations without other competing visual stimuli supporting speed perception. Future research should investigate whether speed perception is indeed a primarily visuospatial control task or whether other sensory information such as auditory factors can have an influence as well.

Effect of Acute Psychological Stress on Speed Perception: An Event-Related Potential Study.

The present study tested the intrinsic ERP features of the effects of acute psychological stress on speed perception. A mental arithmetic task was used to induce acute psychological stress, and the light spot task was used to evaluate speed perception. Compared with judgments in the constant speed and uniform acceleration motion, judgments in the uniform deceleration motion were made more quickly and with higher accuracy; attention control was higher and peaked later; and there was longer N2 peak latency, larger N2 peak amplitude, and lower mean amplitude of the late negative slow wave (SW). Under stress, the reaction time was significantly shorter. The N2 peak amplitude and SW mean amplitude were significantly higher, attention control was higher and appeared earlier, and there was a greater investment of cognitive resources. The type of movement and evoked stress also interacted to predict behavioral and ERP measures. Under acute stress, judgments made in the uniform deceleration motion condition elicited lower N2 peak latency, higher attention control, and later peak attention. The results suggest that judgments of the speed of decelerating motion require a lower investment of cognitive resources than judgments of other kinds of motion, especially under acute stress. These findings are best interpreted in terms of the interaction of arousal and attention.

Optimal integration of kinematic and ball-flight information when perceiving the speed of a moving ball.

In order to intercept a moving target such as a baseball with high spatio-temporal accuracy, the perception of the target's movement speed is important for estimating when and where the target will arrive. However, it is unclear what sources of information are used by a batter to estimate ball speed and how those sources of information are integrated to facilitate successful interception. In this study, we examined the degree to which kinematic and ball-flight information are integrated when estimating ball speed in baseball batting. Thirteen university level baseball batters performed a ball-speed evaluation task in a virtual environment where they were required to determine which of two comparison baseball pitches (i.e., a reference and comparison stimuli) they perceived to be faster. The reference and comparison stimuli had the same physical ball speed, but with different pitching movement speeds in the comparison stimuli. The task was performed under slow (125 km/h) and fast (145 km/h) ball-speed conditions. Results revealed that the perceived ball-speed was influenced by the movement speed of the pitcher's motion, with the influence of the pitcher's motion more pronounced in the fast ball-speed condition when ball-flight information was presumably less reliable. Moreover, exploratory analyses suggested that the more skilled batters were increasingly likely to integrate the two sources of information according to their relative reliability when making judgements of ball speed. The results provide important insights into how skilled performers may make judgements of speed and time to contact, and further enhance our understanding of how the ability to make those judgements might improve when developing expertise in hitting.

Attentional modulations of audiovisual interactions in apparent motion: Temporal ventriloquism effects on perceived visual speed.

The timing of brief stationary sounds has been shown to alter different aspects of visual motion, such as speed estimation. These effects of auditory timing have been explained by temporal ventriloquism and auditory dominance over visual information in the temporal domain. Although previous studies provide unprecedented evidence for the multisensory nature of speed estimation, how attention is involved in these audiovisual interactions remains unclear. Here, we aimed to understand the effects of spatial attention on these audiovisual interactions in time. We utilized a set of audiovisual stimuli that elicit temporal ventriloquism in visual apparent motion and asked participants to perform a speed comparison task. We manipulated attention either in the visual or auditory domain and systematically changed the number of moving objects in the visual field. When attention was diverted to a stationary object in the visual field via a secondary task, the temporal ventriloquism effects on perceived speed decreased. On the other hand, focusing attention on the auditory stimuli facilitated these effects consistently across different difficulty levels of secondary auditory task. Moreover, the effects of auditory timing on perceived speed did not change with the number of moving objects and existed in all the experimental conditions. Taken together, our findings revealed differential effects of allocating attentional resources in the visual and auditory domains. These behavioral results also demonstrate that reliable temporal ventriloquism effects on visual motion can be induced even in the presence of multiple moving objects in the visual field and under different perceptual load conditions.

The perceptual dynamics of the contrast induced speed bias.

In this article we present a temporal extension of the slow motion prior model to generate predictions regarding the temporal evolution of the contrast induced speed bias. We further tested these predictions using a novel experimental paradigm that allows us to measure the dynamic perceptual difference between stimuli through a series of manual pursuit open loop tasks. Results show good agreement with our model's predictions. The main findings reveal that hand speed dynamics are affected by stimulus contrast in a way that is consistent with a dynamic model of motion perception that assumes a slow motion prior. The proposed model also confirms observations made in previous studies that suggest that motion bias persisted even at high contrast as a consequence of the dynamics of the slow motion prior.

The effect of eccentricity on the linear-radial speed bias: Testing the motion-in-depth model.

Radial motion is perceived as faster than linear motion when local spatiotemporal properties are matched. This radial speed bias (RSB) is thought to occur because radial motion is partly interpreted as motion-in-depth. Geometry dictates that a fixed amount of radial expansion at increasing eccentricities is consistent with smaller motion in depth, so it is perhaps surprising that the impact of eccentricity on RSB has not been examined. With this issue in mind, across 3 experiments we investigated the RSB as a function of eccentricity. In a 2IFC task, participants judged which of a linear (test - variable speed) or radial (reference - 2 or 4°/s) stimulus appeared to move faster. Linear and radial stimuli comprised 4 Gabor patches arranged left, right, above and below fixation at varying eccentricities (3.5°-14°). For linear stimuli, Gabors all drifted left or right, whereas for radial stimuli Gabors drifted towards or away from the centre. The RSB (difference in perceived speeds between matched linear and radial stimuli) was recovered from fitted psychometric functions. Across all 3 experiments we found that the RSB decreased with eccentricity but this tendency was less marked beyond 7° - i.e. at odds with the geometry, the effect did not continue to decrease as a function of eccentricity. This was true irrespective of whether stimuli were fixed in size (Experiment 1) or varied in size to account for changes in spatial scale across the retina (Experiment 2). It was also true when we removed conflicting stereo cues via monocular viewing (Experiment 3). To further investigate our data, we extended a previous model of speed perception, which suggests perceived motion for such stimuli reflects a balance between two opposing perceptual interpretations, one for motion in depth and the other for object deformation. We propose, in the context of this model, that our data are consistent with placing greater weight on the motion in depth interpretation with increasing eccentricity and this is why the RSB does not continue to reduce in line with purely geometric constraints.

Development of motion speed perception from infancy to early adulthood: a high-density EEG study of simulated forward motion through optic flow.

This study investigated evoked and oscillatory brain activity in response to forward visual motion at three different ecologically valid speeds, simulated through an optic flow pattern consisting of a virtual road with moving poles at either side of it. Participants were prelocomotor infants at 4-5 months, crawling infants at 9-11 months, primary school children at 6 years, adolescents at 12 years, and young adults. N2 latencies for motion decreased significantly with age from around 400 ms in prelocomotor infants to 325 ms in crawling infants, and from 300 and 275 ms in 6- and 12-year-olds, respectively, to 250 ms in adults. Infants at 4-5 months displayed the longest latencies and appeared unable to differentiate between motion speeds. In contrast, crawling infants at 9-11 months and 6-year-old children differentiated between low, medium and high speeds, with shortest latency for low speed. Adolescents and adults displayed similar short latencies for the three motion speeds, indicating that they perceived them as equally easy to detect. Time-frequency analyses indicated that with increasing age, participants showed a progression from low- to high-frequency desynchronized oscillatory brain activity in response to visual motion. The developmental differences in motion speed perception are interpreted in terms of a combination of neurobiological development and increased experience with self-produced locomotion. Our findings suggest that motion speed perception is not fully developed until adolescence, which has implications for children's road traffic safety.

Risk to workers or vehicle damage: What makes drivers slow down in work zones?

OBJECTIVE: Speeding in work zones is common and poses significant safety hazards to motorists and workers. Previous studies have demonstrated that speeding is reduced when workers are visible to the drivers, suggesting that concern for the safety of workers influences drivers' speed choice. Conversely, the extent of speeding when workers are not visible suggests that drivers underestimate the increased risk of crashes or other damage to their vehicles associated with the poorer road conditions common at roadworks (loose surfaces and debris, narrower lane width and drop-offs etc.). To better understand the factors influencing drivers' speeds in work zones, this paper examined the extent to which drivers' speed choices are influenced by their perceived likelihoods of injuring workers and damaging their own vehicles. METHODS: Driver-nominated speeds and perceived likelihoods of worker injury and vehicle damage were collected in an online survey of 405 drivers from Queensland, Australia, by showing photographs of 12 real-world work zones. The data were analyzed using regression techniques to examine the factors influencing driver-nominated speeds and likelihood of speeding. RESULTS: The results supported the hypothesis that both drivers' perceived likelihood of injuring workers and damaging vehicles strongly influence their nominated speeds (p < 0.001). Young and middle-aged drivers nominated 2.5-6.3 km/h higher speeds than older drivers (p < 0.001). Car drivers who also held truck licenses nominated 4.5 km/h higher speeds (p < 0.001) and 81% higher odds of nominating speeds higher than posted limits (p < 0.001) than car-only licensed drivers. Drivers nominated lower speeds at road curves (12.1 km/h lower speed and 53% lower odds of speeding, p < 0.001), if adjacent areas of travel lanes were unpaved or had loose materials (11.5 km/h lower speed and 66% lower odds, p < 0.001), and when workers were visible in work zones (1.4 km/h lower speed, p = 0.004, and 27% lower odds, p = 0.041). CONCLUSIONS: In addition to driver demographic and work zone characteristics, drivers' perceptions of safe speeds depend on their perceptions of the likelihood of worker injury and vehicle damage at work zones. These findings suggest that interventions to heighten drivers' perceptions of the likelihood of damage to their vehicles may be useful in moderating speeds at roadworks.

Ensemble coding of crowd speed using biological motion.

The accurate perception of human crowds is integral to social understanding and interaction. Previous studies have shown that observers are sensitive to several crowd characteristics such as average facial expression, gender, identity, joint attention, and heading direction. In two experiments, we examined ensemble perception of crowd speed using standard point-light walkers (PLW). Participants were asked to estimate the average speed of a crowd consisting of 12 figures moving at different speeds. In Experiment 1, trials of intact PLWs alternated with trials of scrambled PLWs with a viewing duration of 3 seconds. We found that ensemble processing of crowd speed could rely on local motion alone, although a globally intact configuration enhanced performance. In Experiment 2, observers estimated the average speed of intact-PLW crowds that were displayed at reduced viewing durations across five blocks of trials (between 2500 ms and 500 ms). Estimation of fast crowds was precise and accurate regardless of viewing duration, and we estimated that three to four walkers could still be integrated at 500 ms. For slow crowds, we found a systematic deterioration in performance as viewing time reduced, and performance at 500 ms could not be distinguished from a single-walker response strategy. Overall, our results suggest that rapid and accurate ensemble perception of crowd speed is possible, although sensitive to the precise speed range examined.

Action-induced changes in the perceived temporal features of visual events.

Perceived duration can be subject to deviations around the time of a voluntary action. Whether the mechanisms underlying action-induced visual duration effects are effector-specific or require a more generalized action-linked multimodal calibration with the transient visual system, however, is a question yet to be answered. Here, we investigate this using dynamic visual stimuli presented as contingent upon the execution of an arbitrarily associated voluntary manual response. Our results demonstrate that the duration of intervals with arbitrarily associated keypress-visual event pair is perceived as shorter than the duration in a pure visual condition, where the same stimuli are rather passively observed without the execution of a concurrent action. Whereas the control experiments show that motor memory and attention cannot explain the action-induced changes in perceived temporal features, action-induced changes in perceived speed are dissociated from those in perceived duration, and that the duration compression disappears using isoluminant or static stimuli, which together provide evidence that these two effects can be modulated in the motion-processing units, although via separate neural mechanisms.

The effect of video playback speed on surgeon technical skill perception.

PURPOSE:  Finding effective methods of discriminating surgeon technical skill has proved a complex problem to solve computationally. Previous research has shown that obtaining non-expert crowd evaluations of surgical performances is as accurate as the gold standard, expert surgeon review. The aim of this research is: (1) to learn whether crowdsourced evaluators give higher ratings of technical skill to video of performances with increased playback speed, (2) its effect in discriminating skill levels, and (3) whether this increase is related to the evaluator consciously being aware that the video is manually manipulated. METHODS:  A set of ten peg transfer videos (five novices, five experts) were used to evaluate the perceived technical skill of the performers at each video playback speed used ([Formula: see text]). Objective metrics used for measuring technical skill were also computed for comparison by manipulating the corresponding kinematic data of each performance. Two videos of an expert and novice performing dry laboratory laparoscopic trials of peg transfer tasks were used to obtain evaluations at each playback speed ([Formula: see text]) of perception of whether a video is played at real-time playback speed or not. RESULTS:  We found that while both novices and experts had increased perceived technical skill as the video playback was increased, the amount of increase was significantly greater for experts. Each increase in the playback speed by [Formula: see text] was associated with, on average, a 0.72-point increase in the GOALS score (95% CI 0.60-0.84 point increase; [Formula: see text]) for expert videos and only a 0.24-point increase in the GOALS score (95% CI 0.13-0.36 point increase; [Formula: see text]) for novice videos. CONCLUSION:  Due to the differential increase in perceived technical skill due to increased playback speed for experts, the difference between novice and expert skill levels of surgical performances may be more easily discerned by manually increasing the video playback speed.

Speed Overestimation of the Moving Away Object in the Intentional Reaction Causal Effect.

We describe a new illusory speed effect arising in visual events developed by Michotte (1946/1963) in studies of causal perception and, more specifically, within the so-called intentional reaction effect: When an Object B is seen intentionally escaping from another Object A, its perceived speed is overestimated. In Experiment 1, we used two-alternative forced choice comparisons to estimate perceived speed scale values for a small square moving either alone or in different contexts known to elicit different impressions of animacy (Parovel et al., 2018). The results showed that B's speed was overestimated only in the condition in which it moved away from another approaching square moving in a nonrigid way, like a caterpillar. In Experiment 2, we psychophysically measured the magnitude of speed overestimation in that condition and tested whether it could be affected by further animacy cues related to the escaping object (the actual velocity of the square) and to the approaching square (its type of motion: caterpillar or linear). Results confirmed that B's speed was overestimated up to 10% and that the degree of overestimation was affected by both experimental factors, being greater at higher speeds and when the chasing object moved in an animate fashion. This speed bias might be related to a higher sensitivity of the visual processes to threat-related events such as fighting and chasing, leading to evolutionary adaptive behaviours such as speedy flight from predators, but also empathy and emotion understanding.

Discriminação de velocidades de veículos por observadores parados / Discriminación de velocidades de vehículos por observadores estáticos / Discrimination of vehicle speeds by stationary observers

A percepção de movimento é objeto de estudo da psicofísica, entretanto há poucos estudos em situações naturalísticas ou que utilizam veículos reais. Investigamos como as pessoas percebem a velocidade de veículos em situações naturais. Observadores estáticos foram solicitados a determinar a velocidade de um veículo real em movimento. Os resultados demonstraram acurácia nas estimativas das velocidades dos veículos, independente do sexo do participante e de possuir ou não habilitação. O expoente da função-potência associado a esta dimensão foi de 1,31, mostrando tendência à superestimativa com o aumento da velocidade física, indicando que não há linearidade na percepção de velocidades de veículos por observadores estáticos.

The perception of movement is an object of study of psychophysics, however there are few studies in naturalistic situations or using real vehicles. We investigated how people perceive vehicle speed in natural situations. Static observers were asked to determine the speed of a real moving vehicle. The results showed accuracy in the estimates of vehicle speeds, regardless of the participant's gender and whether or not they are licensed. The exponent of the power-function associated with this dimension was 1.31, showing a tendency to overestimate with increasing physical speed, indicating that there is no linearity in the perception of vehicle speeds by static observers

La percepción del movimiento es objeto de estudio de la psicofísica, sin embargo, existen pocos estudios en situaciones naturalistas o utilizando vehículos reales. Investigamos cómo personas perciben la velocidad del vehículo en situaciones naturales. Se pidió a observadores estáticos que determinaran la velocidad de vehículos en movimiento real. Los resultados mostraron precisión en las estimaciones de la velocidad, independientemente del género del participante y si tiene licencia o no. El exponente de la función de potencia asociado con esta dimensión fue 1.31, mostrando una tendencia a sobreestimar con el aumento de la velocidad física, lo que indica que no existe linealidad en la percepción de la velocidad del vehículo por parte de los observadores estáticos.

Influence of the Size of the Field of View on Visual Perception While Running in a Treadmill-Mediated Virtual Environment.

We investigated how the size of the horizontal field of view (FoV) affects visual speed perception with individuals running on a treadmill. Twelve moderately trained to trained participants ran on a treadmill at two different speeds (8 and 12 km/h) in front of a moving virtual scene. Different masks were used to manipulate the visible visual field, masking either the central or the peripheral area of the virtual scene or showing the full visual field. We asked participants to match the visual speed of the scene to their actual running speed. For each trial, participants indicated whether the scene was moving faster or slower than they were running. Visual speed was adjusted according to the responses using a staircase method until the Point of Subjective Equality was reached, that is until visual and running speed were perceived as matching. For both speeds and all FoV conditions, participants underestimated visual speed relative to the actual running speed. However, this underestimation was significant only when the peripheral FoV was masked. These results confirm that the size of the FoV should absolutely be taken into account for the design of treadmill-mediated virtual environments (VEs).

Drivers' estimation of their travelling speed: a study on an expressway and a local road.

Correctly estimating the travelling speed is essential for safety on the roads to ensure safer interactions with other drivers and to avoid violations of traffic regulations. Therefore, it is important to create understanding of the pattern of speed perception of drivers and the influencing factors. This study invited 40 drivers to participate in a field experiment measuring speed perception. The experiment was conducted using a test car equipped with high fidelity Global Positioning System (GPS). Data were collected for two settings (hidden versus revealed speedometer) and four requested speeds (50, 70, 80 and 100 km/h). An analysis of variance test was conducted along with separate t-tests and cumulative distributions for each speed independently. The results clearly show that there were significant differences in perceived speed between a hidden and revealed speedometer, between the first and second trial and among all the requested speeds. Participants drove significantly faster for all the requested speeds in the hidden speedometer setting. This shows that participants underestimated their speed. In case of complex situations, drivers may not be able to rely on speedometers and may cause a violation of law, unintentionally. Therefore, it is recommended to jurisdictions to consider these results while making decisions regarding speed management.

Perceived speed of motion in depth modulates misjudgements of approaching trajectories consistently with a slow prior.

Previous studies have shown that the angle of approach is consistently overestimated for approaching (but passing-by) objects. An explanation based on a slow-motion prior has been proposed in the past to account for this bias. The mechanism relies on the (less reliable) in-depth component of the motion being more attracted towards the slow motion prior than the (more reliable) lateral component. This hypothesis predicts that faster speeds in depth will translate into a greater bias if the perception of velocity in depth follows Weber's law. Our approach is different than the one used in previous studies where perceived speed and direction were measured in different experiments. To test our hypothesis, we conducted an experiment in which participants estimated approaching angles via a pointing device, while at the same time comparing the speed of the approaching object with a lateral velocity reference. This way, we couple perceived speed with perceived trajectory for each approaching angle in the same trial. Our results show that the directional bias is larger for faster objects, which is consistent with motion in depth following Weber's law. The differential biases can be accounted for by a Bayesian model that includes a slow motion prior.

Using road markings as a continuous cue for speed choice.

The potential for using road markings to indicate speed limits was investigated in a driving simulator over the course of two sessions. Two types of experimental road markings, an "Attentional" set designed to provide visually distinct cues to indicate speed limits of 60, 80 and 100 km/h, and a "Perceptual" set designed to also affect drivers' perception of speed, were compared to a standard undifferentiated set of markings. Participants (n = 20 per group) were assigned to one of four experimental groups (Attentional-Explicit, Attentional-Implicit, Perceptual-Explicit, Perceptual-Implicit) or a Control group (n = 22; standard road markings). The Explicit groups were instructed about the meaning of the road markings while those in the Implicit and Control groups did not receive any explanation. Participants drove five 10 km simulated roads containing three speed zones (60, 80 and 100 km/h) during the first session. The participants returned to the laboratory approximately 3 days later to drive five more trials including roads they had not seen before, a trial that included a secondary task, and a trial where speed signs were removed and only markings were present. The findings indicated that both types of road markings improved drivers' compliance with speed limits compared to the control group, but that explicit instruction as to the meaning of the markings was needed to realise their full benefit. Although previous research has indicated the benefit of road markings used as warnings to indicate speed reductions in advance of horizontal or vertical curves, the findings of the present experiment also suggest that systematically associating road markings with specific speed limits may be a useful way to improve speed limit compliance and increase speed homogeneity.

Temporal ventriloquism along the path of apparent motion: speed perception under different spatial grouping principles.

The coordination of intramodal perceptual grouping and crossmodal interactions plays a critical role in constructing coherent multisensory percepts. However, the basic principles underlying such coordinating mechanisms still remain unclear. By taking advantage of an illusion called temporal ventriloquism and its influences on perceived speed, we investigated how audiovisual interactions in time are modulated by the spatial grouping principles of vision. In our experiments, we manipulated the spatial grouping principles of proximity, uniform connectedness, and similarity/common fate in apparent motion displays. Observers compared the speed of apparent motions across different sound timing conditions. Our results revealed that the effects of sound timing (i.e., temporal ventriloquism effects) on perceived speed also existed in visual displays containing more than one object and were modulated by different spatial grouping principles. In particular, uniform connectedness was found to modulate these audiovisual interactions in time. The effect of sound timing on perceived speed was smaller when horizontal connecting bars were introduced along the path of apparent motion. When the objects in each apparent motion frame were not connected or connected with vertical bars, the sound timing was more influential compared to the horizontal bar conditions. Overall, our findings here suggest that the effects of sound timing on perceived speed exist in different spatial configurations and can be modulated by certain intramodal spatial grouping principles such as uniform connectedness.