Time dilation caused by static images with implied motion

Perception of complex Glass patterns through spatial summation across unique frames

When processing visual information from the surroundings, human vision depends on the constant integration of form and motion cues. Dynamic Glass patterns (GPs) may be used to study how such visual integration occurs in the human visual system. Dynamic GPs are visual stimuli composed of two or more unique frames consisting of different configurations of dot pairs, called dipoles, presented in rapid succession. Previous psychophysical studies showed that the discrimination of translational and circular dynamic GPs is influenced by both the number of unique frames and the pattern update rate. In this study, we manipulated these two variables to assess their influence on the discrimination threshold of circular, radial, and spiral GPs, partially replicating previous findings on circular GPs. Our results indicate that circular GPs are more easily perceived than radial and spiral GPs, showing lower discrimination thresholds. Furthermore, we found that discrimination thresholds vary as a function of the number of unique frames but not as a function of the pattern update rate. Specifically, coherence thresholds decreased with increasing the number of unique frames. In conclusion, our findings support the existence of spatial summation of form signals coming from the unique frames that generate complex GPs. On the other hand, they do not support temporal integration of local form-motion signals based on the pattern update rate.

An Illusory Motion in Stationary Stimuli Alters Their Perceived Duration

Despite having equal duration, stimuli in physical motion are perceived to last longer than static ones. Here, we investigate whether illusory motion stimuli produce a time-dilation effect similar to physical motion. Participants performed a duration discrimination task that compared the perceived duration of static stimuli with and without illusory motion to a reference stimulus. In the first experiment, we observed a 4% increase in the number of "longer" responses for the illusory motion images than static stimuli with equal duration. The time-dilation effect, quantified as a shift in the Point of Subjective Equality (PSE), was approximately 55 ms for a 2-second stimulus. Although small, the effect was replicated in a second experiment in which the total number of standard-duration repetitions was reduced from 73 to 19. In the third experiment, we found a positive linear trend between the strength of the illusory motion and the magnitude of the time-dilation effect. These results demonstrate that, similar to physical motion stimuli, illusory motion stimuli are perceived to last longer than static stimuli. Furthermore, the strength of the illusion influences the extent of the lengthening of perceived duration.

A comparison of equivalent noise methods in investigating local and global form and motion integration

Static and dynamic cues within certain spatiotemporal proximity are used to evoke respective global percepts of form and motion. The limiting factors in this process are, first, internal noise, which indexes local orientation/direction detection, and, second, sampling efficiency, which relates to the processing and the representation of global orientation/direction. These parameters are quantified using the equivalent noise (EN) paradigm. EN has been implemented with just two levels: high and low noise. However, when using this simplified version, one must assume the shape of the overall noise dependence, as the intermediate points are missing. Here, we investigated whether two distinct EN methods, the 8-point and the simplified 2-point version, reveal comparable parameter estimates. This was performed for three different types of stimuli: random dot kinematograms, and static and dynamic translational Glass patterns, to investigate how constant internal noise estimates are, and how sampling efficiency might vary over tasks. The results indicated substantial compatibility between estimates over a wide range of external noise levels sampled with eight data points, and a simplified version producing two highly informative data points. Our findings support the use of a simplified procedure to estimate essential form-motion integration parameters, paving the way for rapid and critical applications to populations that cannot tolerate protracted measurements.

Changes in face category induce stronger duration distortion in the temporal oddball paradigm

A novel stimulus embedded in a sequence of repeated stimuli is often perceived to be longer in duration. Studies have indicated the involvement of repetition suppression in this duration distortion, but it remains unclear which processing stages are important. The present study examined whether high-level visual category processing contributes to the oddball's duration distortion. In Experiment 1, we presented a novel face image in either human, monkey, or cat category after a repetition of an identical human face image in the temporal oddball paradigm. We found that the duration distortion of the last stimulus increased when the face changed across different categories, than when it changed within the same category. However, the effect of category change disappeared when globally scrambled and locally scrambled face images were used in Experiments 2 and 3, respectively, suggesting that the difference in duration distortion cannot be attributed to low-level visual properties of the images. Furthermore, in Experiment 4, we again used intact face images and found that category changes can influence the duration distortion even when a series of different human faces was presented before the last stimulus. These findings indicate that high-level visual category processing plays an important role in the duration distortion of oddballs. This study supports the idea that visual processing at higher visual stages is involved in duration perception. (219 words).

Perceptual confidence of visual stimulus features is associated with duration perception

It has been shown that the perceived duration of an object in the subsecond range is closely associated with its nontemporal perceptual properties, the mechanism under which remains unclear. Previous studies have revealed a modulatory effect of early visual feature processing on the apparent duration. Here, we further examined the relationship between perceptual confidence and subjective time by asking participants to simultaneously perform temporal and nontemporal perceptual judgments. The results revealed a significant effect on confidence levels. When participants' confidence in judging the coherent motion direction or relative dot numerosity increases, their perceived duration of the stimulus also appears longer. These results are discussed in the context of perceptual evidence accumulation and evaluation for the decision-making of perceptual properties. They suggest a profound contribution of object processing to the computation of subjective time and provide further insights into the mechanism of event timing.

Vestibular Stimulation Causes Contraction of Subjective Time

As the cerebellum is involved in vestibular and time-keeping processes, we asked if the latter are related. We conducted three experiments to investigate the effects of vestibular stimulation on temporal processing of supra-second durations. In Experiment 1, subjects had to perform temporal productions of 10- and 15-s intervals either standing on both feet or while being engaged in the difficult balancing task of standing on one foot with their eyes closed (or open for control purposes). In Experiment 2, participants were required to produce intervals of 5, 10, 15, and 20 s while standing on both feet with their eyes open or closed, which constituted an easier balancing task. In Experiment 3, we removed the active balancing; temporal productions of the same four durations had to be performed with the eyes open or closed during the passive vestibular stimulation induced by the oscillatory movements of a swing. Participants produced longer intervals when their eyes were closed, but active balancing was not the culprit. On the contrary, temporal over-production was particularly pronounced during the passive vestibular stimulation brought about by the swing movements. Taken together, the experiments demonstrate that the contraction of the subjective time during balancing tasks with closed eyes is most likely of vestibular origin.

The Effects of Speed-Modulated Visual Stimuli Seen through Smart Glasses on Work Efficiency after Viewing

It is known that subjective time and work efficiency are affected by visual stimuli. However, existing studies only consider the effects of visual information on the user during viewing and ignore the after effects. Using smart glasses lets users see visual information while moving until just before arriving at the office or school. We hypothesize that the user’s effects from the visual information they were looking at just before working or studying affects the subsequent work. Through two user studies, we investigated whether information presented on smart glasses affected subsequent work efficiency. In the first experiment, participants were presented with avatars running at two levels of speed, or no avatars, through simulated smart glasses in a virtual environment. They then solved a dot-clicking task on a desktop monitor. In the second experiment, we investigated whether the same effect could be shown while walking in the real environment, with a running and a fast-walking avatar both at the same speed in order to see the difference in the effects of the different movements. In the first experiment, we confirmed that the speed of later work tended to improve when presenting the running human-shaped avatar. From the results of the second experiment, which was conducted in the real environment, we did not confirm that the subsequent work speed varied depending on the type of avatar being displayed. As a reason for the trend of improvement in the task efficiency in the first experiment, observation of fast human motion may have unconsciously accelerated the observers’ body movement speed due to the mirror neuron mechanism. As a reason for why the work speed did not improve in the second experiment, the participants may be affected by other pedestrians and running cars. Additionally, it was difficult to see the images on the smart glasses while walking in the real environment.

The Varying Coherences of Implied Motion Modulates the Subjective Time Perception

Previous research has demonstrated that duration of implied motion (IM) was dilated, whereas hMT+ activity related to perceptual processes on IM stimuli could be modulated by their motion coherence. Based on these findings, the present study aimed to examine whether subjective time perception of IM stimuli would be influenced by varying coherence levels. A temporal bisection task was used to measure the subjective experience of time, in which photographic stimuli showing a human moving in four directions (left, right, toward, or away from the viewer) were presented as probe stimuli. The varying coherence of these IM stimuli was manipulated by changing the percentage of pictures implying movement in one direction. Participants were required to judge whether the duration of probe stimulus was more similar to the long or short pre-presented standard duration. As predicted, the point of subjective equality was significantly modulated by the varying coherence of the IM stimuli, but not for no-IM stimuli. This finding suggests that coherence level might be a key mediating factor for perceived duration of IM images, and top-down perceptual stream from inferred motion could influence subjective experience of time perception.

A Directional Congruency Effect of Amplified Dilated Time Perception Induced by Looming Stimuli With Implied Motion Cues

The perception of time is not veridical, but, rather, it is susceptible to environmental context, like the intrinsic dynamics of moving stimuli. The direction of motion has been reported to affect time perception such that movement of objects toward an observer (i.e., looming stimuli) is perceived as longer in duration than movement of objects away from the observer (i.e., receding stimuli). In the current study we investigated whether this looming/receding temporal asymmetry can be modulated by the direction of movement implied by static cues of images. Participants were presented with images of a running person, rendered from either the front or the back (i.e., representing movement toward or away from the observer). In Experiment 1, the size of the images was constant. In Experiment 2, the image sizes varied (i.e., increasing: looming; or decreasing: receding). In both experiments, participants performed a temporal bisection task by judging the duration of the image presentation as "short" or "long". In Experiment 1, we found no influence of implied-motion direction in the participants' duration perceptions. In Experiment 2, however, participants overestimated the duration of the looming, as compared to the receding image in relation to real motion. This finding replicated previous findings of the looming/receding asymmetry using naturalistic human-character stimuli. Further, in Experiment 2 we observed a directional congruency effect between real and implied motion; stimuli were perceived as lasting longer when the directions of real and implied motion were congruent versus when these directions were incongruent. Thus, looming (versus receding) movement, a perceptually salient stimulus, elicits differential temporal processing, and higher-order motion processing integrates signals of real and implied motion in time perception.

An Event-Related Potential Study of the Neural Response to Inferred Motion in Visual Images of Varying Coherence

A vivid sense of motion can be inferred from static pictures of objects in motion. Like perception of real motion (RM), viewing photographs with implied motion (IM) can also activate the motion-sensitive visual cortex, including the middle temporal complex (hMT+) of the human extrastriate cortex. Moreover, extrastriate cortical activity also increases with motion coherence. Based on these previous findings, this study examined whether similar coherence level-dependent activity in motion-sensitive human extrastriate cortex is seen with IM stimuli of varying coherence. Photographic stimuli showing a human moving in four directions (left, right, toward, or away from the viewer) were presented to 15 participants. The coherence of the stimuli was manipulated by changing the percentage of pictures implying movement in one direction. Electroencephalographic data were collected while participants viewed IM or counterpart non-IM stimuli. The P2 response of extrastriate visual cortex (source located at hMT+) increased bilaterally with coherence level in the IM conditions but not in the non-IM conditions. This finding demonstrates that extrastriate visual cortical responses are progressively activated as motion coherence increases, even when motion is inferred, providing new support for the view that the activity of human motion-sensitive extrastriate visual cortex can be modulated by top-down perceptual influences in addition to its well-established role in processing bottom-up sensory signals.

Move Still: The Effects of Implied and Real Motion on the Duration Estimates of Dance Steps

It has been argued that movement can be implied by static cues of images depicting an instance of a dynamic event. Instances of implied motion have been investigated as a special type of stimulus with common processing mechanisms to those of real motion. Timing studies have reported a lengthening of the perceived time for moving as opposed to static stimuli and for stimuli of higher as compared to lower amounts of implied motion. However, the actual comparison of real versus implied motion on timing has never been investigated. In the present study, we compared directly the effect of two hypothetically analogous ballet steps with different amounts of movement and static instances of the dynamic peak of these events in a reproduction task. The analysis revealed an overestimation and lower response variability for real as compared to implied motion stimuli. These findings replicate and extend the apparent duration lengthening for moving as compared to static stimulation, even for static images containing implied motion, questioning whether or not the previously reported correspondence between real and implied motion transfers in the timing domain. This lack of correspondence was further supported by the finding that the amount of movement presented affected only displays of real motion.

Time dilation effect in an active observer and virtual environment requires apparent motion: No dilation for retinal- or world-motion alone

It is known that moving visual stimuli are perceived to last longer than stationary stimuli with the same physical duration (Kanai, Paffen, Hogendoorn, & Verstraten, 2006), and that motor actions (Tomassini & Morrone, 2016) and eye movements (Morrone, Ross, & Burr, 2005) can alter perceived duration. In the present work, we investigated the contributions of stimulus motion and self-motion to perceived duration while observers stood or walked in a virtual reality environment. Using a visual temporal reproduction task, we independently manipulated both the participants' motion (stationary or walking) and the stimulus motion (retinal stationary, real-world stationary and negative double velocity). When the observers were standing still, drifting gratings were perceived as lasting longer than duration-matched static gratings. Interestingly, we did not see any time distortion when observers were walking, neither when the gratings were kept stationary relative to the observer's point of view (i.e., no retinal motion) nor when they were stationary in the external world (i.e., producing the same retinal velocity as the walking condition with stationary grating). Self-motion caused significant dilation in perceived duration only when the gratings were moving at double speed, opposite to the observers' walking direction. Consistent with previous work (Fornaciai, Arrighi, & Burr, 2016), this suggests that the system is able to suppress self-generated motion to enhance external motion, which would have ecological benefits, for example, for threat detection while navigating through the environment.

Feature-based attentional selection affects the perceived duration of a stimulus having two superposed patterns

The perceived duration of a visual event is highly related to stimulus attributes. It is well known that a moving stimulus appears to last longer than a static one does. Previous studies have demonstrated that the time dilation in a moving stimulus can be influenced by perceived motion, rather than by mere physical motion, and that a faster motion appears to last longer than a slower one does. However, whether a top-down attentional set for the feature value can modulate the time dilation in a moving stimulus when two different visual patterns coexist within the same region of the visual field is still unknown. To test this, in Experiment 1, we presented a moving and a static random-dot pattern simultaneously within the same region, and instructed the observer to attend to one of these two patterns. The results demonstrate that perceived duration was longer when attention was directed to the moving, rather than static pattern, although both patterns physically coexisted at the same time and place and for the same duration. In Experiment 2, slow and/or fast moving patterns were presented at the same time and place, and again, feature-based attentional selection affected the perceived duration of the identical physical display. These results suggest that attention to a moving stimulus is an essential factor that determines the time dilation in a moving stimulus. This study revealed that feature-based attention, as opposed to location-based attention, plays an important role in motion-induced time dilation.

Dilation and Constriction of Subjective Time Based on Observed Walking Speed

The physical properties of events are known to modulate perceived time. This study tested the effect of different quantitative (walking speed) and qualitative (walking-forward vs. walking-backward) features of observed motion on time perception in three complementary experiments. Participants were tested in the temporal discrimination (bisection) task, in which they were asked to categorize durations of walking animations as "short" or "long." We predicted the faster observed walking to speed up temporal integration and thereby to shift the point of subjective equality leftward, and this effect to increase monotonically with increasing walking speed. To this end, we tested participants with two different ranges of walking speeds in Experiment 1 and 2 and observed a parametric effect of walking speed on perceived time irrespective of the direction of walking (forward vs. rewound forward walking). Experiment 3 contained a more plausible backward walking animation compared to the rewound walking animation used in Experiments 1 and 2 (as validated based on independent subjective ratings). The effect of walking-speed and the lack of the effect of walking direction on perceived time were replicated in Experiment 3. Our results suggest a strong link between the speed but not the direction of perceived biological motion and subjective time.

How does nature exposure make people healthier?: Evidence for the role of impulsivity and expanded space perception

Nature exposure has been linked to a plethora of health benefits, but the mechanism for this effect is not well understood. We conducted two studies to test a new model linking the health benefits of nature exposure to reduced impulsivity in decision-making (as measured by delay discounting) via psychologically expanding space perception. In study 1 we collected a nationwide U.S. sample (n = 609) to determine whether nature exposure was predictive of health outcomes and whether impulsive decision-making mediated the effect. Results indicated that Nature Accessibility and Nature Exposure From Home significantly predicted reduced scores on the Depression, Anxiety, Stress Scales (DASS) (p < .001, p = .03, respectively) and improved general health and wellbeing (p < .001, p < .01, respectively). Nature Accessibility also predicted reduced impulsive decision-making (p < .01), and Nature Accessibility showed significant indirect effects through impulsive decision-making on both the DASS (p = .02) and general health and wellbeing (p = .04). In Study 2, a lab-based paradigm found that nature exposure expanded space perception (p < .001), and while the indirect effect of nature exposure through space perception on impulsive decision-making did not meet conventional standards of significance (p < .10), the pattern was consistent with hypotheses. This combination of ecologically-valid and experimental methods offers promising support for an impulsivity-focused model explaining the nature-health relationship.

Watching a real moving object expands tactile duration: the role of task-irrelevant action context for subjective time

Although it is well established that action contexts can expand the perceived durations of action-related events, whether action contexts also impact the subjective duration of events unrelated to the action remains an open issue. Here we examined how the automatic implicit reactions induced by viewing task-irrelevant, real moving objects influence tactile duration judgments. Participants were asked to make temporal bisection judgments of a tactile event while seeing a potentially catchable swinging ball. Approaching movement induced a tactile-duration overestimation relative to lateral movement and to a static baseline, and receding movement produced an expansion similar in duration to that from approaching movement. Interestingly, the effect of approaching movement on the subjective tactile duration was greatly reduced when participants held lightweight objects in their hands, relative to a hands-free condition, whereas no difference was obtained in the tactile-duration estimates between static hands-free and static hands-occupied conditions. The results indicate that duration perception is determined by internal bodily states as well as by sensory evidence.

Effect of motion coherence on time perception relates to perceived speed

The present study examined the effect of coherence of moving visual objects on time perception. Participants observed stimuli composed of four line segments moving behind or in front of occluders. The line segments appeared to move either coherently as a diamond outline or incoherently, depending on the occlusion. Results from the temporal bisection task indicated that the duration of the coherently moving stimulus was perceived longer or shorter compared to the duration of the incoherently moving stimulus depending on the stimulus configurations. The speed comparison task revealed that the trend of the difference in perceived speed between the coherent and incoherent motions in each stimulus configuration was consistent with that of the difference in perceived duration between them. These results demonstrate the effect of motion coherence on perceived duration, and that this effect may be mediated by changes in perceived speed. Our finding provides evidence supporting the involvement of global motion processing in time perception.

Temporal perception in visual processing as a research tool

Accumulated evidence has shown that the subjective time in the sub-second range can be altered by different factors; some are related to stimulus features such as luminance contrast and spatial frequency, others are processes like perceptual grouping and contextual modulation. These findings indicate that temporal perception uses neural signals involved in non-temporal feature processes and that perceptual organization plays an important role in shaping the experience of elapsed time. We suggest that the temporal representation of objects can be treated as a feature of objects. This new concept implies that psychological time can serve as a tool to study the principles of neural codes in the perception of objects like “reaction time (RT).” Whereas “RT” usually reflects the state of transient signals crossing decision thresholds, “apparent time” in addition reveals the dynamics of sustained signals, thus providing complementary information of what has been obtained from “RT” studies.

How long did it last? You would better ask a human

In the future, human-like robots will live among people to provide company and help carrying out tasks in cooperation with humans. These interactions require that robots understand not only human actions, but also the way in which we perceive the world. Human perception heavily relies on the time dimension, especially when it comes to processing visual motion. Critically, human time perception for dynamic events is often inaccurate. Robots interacting with humans may want to see the world and tell time the way humans do: if so, they must incorporate human-like fallacy. Observers asked to judge the duration of brief scenes are prone to errors: perceived duration often does not match the physical duration of the event. Several kinds of temporal distortions have been described in the specialized literature. Here we review the topic with a special emphasis on our work dealing with time perception of animate actors versus inanimate actors. This work shows the existence of specialized time bases for different categories of targets. The time base used by the human brain to process visual motion appears to be calibrated against the specific predictions regarding the motion of human figures in case of animate motion, while it can be calibrated against the predictions of motion of passive objects in case of inanimate motion. Human perception of time appears to be strictly linked with the mechanisms used to control movements. Thus, neural time can be entrained by external cues in a similar manner for both perceptual judgments of elapsed time and in motor control tasks. One possible strategy could be to implement in humanoids a unique architecture for dealing with time, which would apply the same specialized mechanisms to both perception and action, similarly to humans. This shared implementation might render the humanoids more acceptable to humans, thus facilitating reciprocal interactions.