The effects of familiar size and object trajectories on time-to-contact judgements

Hosking, Simon; Crassini, Boris

doi:10.1007/s00221-010-2258-7

Cited by 28 publications

(24 citation statements)

References 41 publications

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“…Since the image will grow at a lower rate than expected the new threshold is reached at a later time than it would the real image of a football ball. This leads to the overestimation of the TTC in this sort of situation and this very same pattern has been reported for this type of manipulation in Hosking and Crassini (2010) when displaying parabolic trajectories. Although the optical geometry that was used in this study was not exactly the same as in our simulations, our proposal would then be consistent with their results.…”

Section: Discussionsupporting

confidence: 81%

Synergies between optical and physical variables in intercepting parabolic targets

Gómez¹,

López‐Moliner²

2013

Front. Behav. Neurosci.

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Interception requires precise estimation of time-to-contact (TTC) information. A long-standing view posits that all relevant information for extracting TTC is available in the angular variables, which result from the projection of distal objects onto the retina. The different timing models rooted in this tradition have consequently relied on combining visual angle and its rate of expansion in different ways with tau being the most well-known solution for TTC. The generalization of these models to timing parabolic trajectories is not straightforward. For example, these different combinations rely on isotropic expansion and usually assume first-order information only, neglecting acceleration. As a consequence no optical formulations have been put forward so far to specify TTC of parabolic targets with enough accuracy. It is only recently that context-dependent physical variables have been shown to play an important role in TTC estimation. Known physical size and gravity can adequately explain observed data of linear and free-falling trajectories, respectively. Yet, a full timing model for specifying parabolic TTC has remained elusive. We here derive two formulations that specify TTC for parabolic ball trajectories. The first specification extends previous models in which known size is combined with thresholding visual angle or its rate of expansion to the case of fly balls. To efficiently use this model, observers need to recover the 3D radial velocity component of the trajectory which conveys the isotropic expansion. The second one uses knowledge of size and gravity combined with ball visual angle and elevation angle. Taking into account the noise due to sensory measurements, we simulate the expected performance of these models in terms of accuracy and precision. While the model that combines expansion information and size knowledge is more efficient during the late trajectory, the second one is shown to be efficient along all the flight.

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Section: Discussionsupporting

confidence: 81%

Synergies between optical and physical variables in intercepting parabolic targets

Gómez¹,

López‐Moliner²

2013

Front. Behav. Neurosci.

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“…Binocular optic information such as binocular disparity (Rushton and Wann, 1999; Gray and Regan, 2004) can also contribute to extract time-to-contact (TTC) information. As more and more evidence became available for the fact that physical prior information like known size (López-Moliner et al, 2007; López-Moliner and Keil, 2012) or object familiarity (Hosking and Crassini, 2010) seems to be used by the perceptual system to more accurately estimate TTC (that is the remaining time until an object reaches a predefined target such as the observer, a certain point on a screen, etc. ), another physical variable came into focus: (earth) gravity.…”

Section: Gravity Information In Vision Related Processing: What Is Itmentioning

confidence: 99%

Gravity as a Strong Prior: Implications for Perception and Action

Jörges

López‐Moliner

2017

Front. Hum. Neurosci.

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In the future, humans are likely to be exposed to environments with altered gravity conditions, be it only visually (Virtual and Augmented Reality), or visually and bodily (space travel). As visually and bodily perceived gravity as well as an interiorized representation of earth gravity are involved in a series of tasks, such as catching, grasping, body orientation estimation and spatial inferences, humans will need to adapt to these new gravity conditions. Performance under earth gravity discrepant conditions has been shown to be relatively poor, and few studies conducted in gravity adaptation are rather discouraging. Especially in VR on earth, conflicts between bodily and visual gravity cues seem to make a full adaptation to visually perceived earth-discrepant gravities nearly impossible, and even in space, when visual and bodily cues are congruent, adaptation is extremely slow. We invoke a Bayesian framework for gravity related perceptual processes, in which earth gravity holds the status of a so called “strong prior”. As other strong priors, the gravity prior has developed through years and years of experience in an earth gravity environment. For this reason, the reliability of this representation is extremely high and overrules any sensory information to its contrary. While also other factors such as the multisensory nature of gravity perception need to be taken into account, we present the strong prior account as a unifying explanation for empirical results in gravity perception and adaptation to earth-discrepant gravities.

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“…We identified two ways to recover the gravity value from visual and temporal information. The first one relies on successive sampling of visual angle and elevation angle information: It has been shown before that participants quickly establish an accurate representation of the size of virtual objects they deal with (Hosking & Crassini, 2010;López-Moliner, Field, & Wann, 2007;López-Moliner & Keil, 2012). This is facilitated when stereoscopic information is available (as in our case; (Regan & Beverley, 1979).…”

Section: Optic Flow Analysismentioning

confidence: 87%

The Use of Visual Cues in Gravity Judgements on Parabolic Motion

Joerges

Slupinski

López‐Moliner

2018

Preprint

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Evidence suggests that humans rely on an earth gravity prior for sensory-motor tasks like catching or reaching. Even under earthdiscrepant conditions, this prior biases perception and action towards assuming a gravitational downwards acceleration of 9.81 m/s². This can be particularly detrimental in interactions with virtual environments employing earth-discrepant gravity conditions for their visual presentation. The present study thus investigates how sensitive humans are to visually presented gravities and which cues are used to extract the gravity values from the visual scene. To this end, we employed a Two-Interval Forced-Choice Design. In Experiment 1, participants had to judge which of two presented parabolas had the higher underlying gravity. We used two initial vertical velocities, two horizontal velocities and a constant target size. Experiment 2 added a manipulation of the reliability of the target size. Experiment 1 shows that participants are generally not very sensitive to visually presented gravities, with weber fractions of 13 to beyond 30 %. We identified the rate of change of the elevation angle () and the rate of change of the visual angle ( ) as major cues. Experiment 2 suggests furthermore that size variability has a small influence on sensitivity, while at the same time larger size variability increases reliance on ̇ and decreases reliance on . All in all, even though we use all available information, humans are not adept at extracting the governing gravity from a visual scene, which might further impact our capabilities of adapting to earth-discrepant gravity conditions with visual information alone.

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The effects of familiar size and object trajectories on time-to-contact judgements

Cited by 28 publications

References 41 publications

Synergies between optical and physical variables in intercepting parabolic targets

Synergies between optical and physical variables in intercepting parabolic targets

Gravity as a Strong Prior: Implications for Perception and Action

The Use of Visual Cues in Gravity Judgements on Parabolic Motion

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