Speed Biases With Real-Life Video Clips

Abstract

We live almost literally immersed in an artificial visual world, especially motion pictures. In this exploratory study, we asked whether the best speed for reproducing a video is its original, shooting speed. By using adjustment and double staircase methods, we examined speed biases in viewing real-life video clips in three experiments, and assessed their robustness by manipulating visual and auditory factors. With the tested stimuli (short clips of human motion, mixed human-physical motion, physical motion and ego-motion), speed underestimation was the rule rather than the exception, although it depended largely on clip content, ranging on average from 2% (ego-motion) to 32% (physical motion). Manipulating display size or adding arbitrary soundtracks did not modify these speed biases. Estimated speed was not correlated with estimated duration of these same video clips. These results indicate that the sense of speed for real-life video clips can be systematically biased, independently of the impression of elapsed time. Measuring subjective visual tempo may integrate traditional methods that assess time perception: speed biases may be exploited to develop a simple, objective test of reality flow, to be used for example in clinical and developmental contexts. From the perspective of video media, measuring speed biases may help to optimize video reproduction speed and validate “natural” video compression techniques based on sub-threshold temporal squeezing.

Accuracy of Intercepting Moving Tactile Targets

“…When intercepting haptic targets, the sensory resolution depends on the part of the skin that is stimulated. In addition to the random errors due to limited sensory resolution, systematic perceptual errors are also common both when using virtual targets (Rossi, Montanaro, & de’Sperati, 2018) and in real life (Troscianko, Wright, & Wright, 1999). They may be particularly evident under unnatural circumstances (La Scaleia, Zago, Moscatelli, Lacquaniti, & Viviani, 2014).…”

Why Do Actions in Slow Motion Appear to Last Longer? On the Effect of Video Speed Information

“…Recently, research has encountered a new context in which specific temporal properties influence subjective judgments, that is to say videos played in altered speeds, especially in slow motion (e.g., Caruso et al., 2016; de'Sperati & Baud Bovy, 2017; Eagleman, 2004; Kashiwakura & Motoyoshi, 2017; Mather & Breivik, 2020; Mather et al., 2017; Nyman et al., 2017; Rossi et al., 2018; Spitz et al., 2017, 2018). Predominantly in sports, this topic has become particularly relevant, partially due to the ongoing debate about whether video replay is helpful to correctly (re-)evaluate critical situations (Spitz et al., 2017) or might even affect evaluations by biasing referees’ decisions due to temporal misperceptions (Caruso et al., 2016; Spitz et al., 2018).…”

Cortical Resonance to Visible and Invisible Visual Rhythms

“…Thus, it appears that there is a mechanism in the brain that implicitly codes a subjective "right" speed of events. This mechanism seems to be specific to event speed, as judgments of video clip speed and video clip duration are not correlated [2].…”

“…Observers were seated 57 cm in front of a laptop screen. Visual stimuli ( Figure 1) consisted of (i) a video clip (1280 × 720 @ 30 Hz) depicting sea ripples on a beach that we had previously used [2]; and (ii) a random dot kinematogram (RDK) (3000 black and white dots, 67 ms lifetime, 5 deg/s maximal speed, 0% coherence). In order to modulate video speed, the frame-rate of the visual stimulus was sinusoidally modulated (frequency, 1, 2, or 4 Hz; amplitude, 10%, 30%, or 50% of the original frame-rate) by controlling in real time the video frame flipping on the graphics board (Nvidia GTX 1060, Santa Clara, CA, USA).…”

“…The capability of judging the correct speed of a dynamic scene in a video clip is surprisingly poor. We have recently shown that (i) speeding up a soccer match video by as much as 12% goes completely undetected [1]; (ii) there are systematic biases in judging the correct video speed, often consisting of speed underestimation [2]; and (iii) 6-7-year-old children judge videos to be slower, as compared to older children and adults [3]. Thus, it appears that there is a mechanism in the brain that implicitly codes a subjective "right" speed of events.…”