Global and Local Contributions to the Optical Specification of Time to Contact: Observer Sensitivity to Composite Tau

Perception ◽  
10.1068/p3230 ◽  
2002 ◽  
Vol 31 (8) ◽  
pp. 901-924 ◽  
Author(s):  
Reinoud J Bootsma ◽  
Cathy M Craig
Keyword(s):  
Discrimination Performance ◽  
Forced Choice ◽  
Object Motion ◽  
Time To Contact ◽  
Local Expansion ◽  
First Order ◽  
Optical Distance ◽  
Observer Motion ◽  
Environmental Element ◽  
Global And Local

First-order time remaining until a moving observer will pass an environmental element is optically specified in two different ways. The specification provided by global tau (based on the pattern of change of angular bearing) requires that the element is stationary and that the direction of motion is accurately detected, whereas the specification provided by composite tau (based on the patterns of change of optical size and optical distance) does not require either of these. We obtained converging evidence for our hypothesis that observers are sensitive to composite tau in four experiments involving relative judgments of time to passage with forced-choice methodology. Discrimination performance was enhanced in the presence of a local expansion component, while being unaffected when the detection of the direction of heading was impaired. Observers relied on the information carried in composite tau rather than on the information carried in its constituent components. Finally, performance was similar under conditions of observer motion and conditions of object motion. Because composite tau specifies first-order time remaining for a large number of situations, the different ways in which it may be detected are discussed.

Global versus Local Image Expansion in Estimating Time-to-Contact from Complex Optic Flow

Perception ◽  
10.1068/p5271 ◽  
2005 ◽  
Vol 34 (5) ◽  
pp. 577-585 ◽  
Author(s):  
Christos D Giachritsis ◽  
Mike G Harris
Keyword(s):  
Optic Flow ◽  
Local Analysis ◽  
Systematic Effect ◽  
Global Pattern ◽  
Time To Contact ◽  
Local Expansion ◽  
Rotation Rates ◽  
Global And Local ◽  
Local Image ◽  
Image Expansion

Previous work (Harris and Giachritsis 2000, Vision Research40 601–611) has shown that, when global and local image expansion are placed in conflict, estimates of time-to-contact (TTC) are based almost exclusively upon global expansion. Here we extend this finding by demonstrating that global image expansion continues to predominate even under conditions that seem more favourable to a local analysis. We added a global rotation to the stimulus so that the global pattern of expansion was distorted while leaving the local expansion unaffected. Even under relatively high rotation rates (30° s−1), local expansion continued to have little systematic effect upon estimates of TTC.

scholarly journals Global and local expansion of magnetic clouds in the inner heliosphere

2009 ◽  
Vol 509 ◽  
pp. A39 ◽  
Author(s):  
A. M. Gulisano ◽  
P. Démoulin ◽  
S. Dasso ◽  
M. E. Ruiz ◽  
E. Marsch
Keyword(s):  
Magnetic Clouds ◽  
Local Expansion ◽  
Global And Local ◽  
Inner Heliosphere

Estimating discrimination performance in two-alternative forced choice tasks: Routines for MATLAB and R

2012 ◽  
Vol 44 (4) ◽  
pp. 1157-1174 ◽  
Author(s):  
Karin M. Bausenhart ◽  
Oliver Dyjas ◽  
Dirk Vorberg ◽  
Rolf Ulrich
Keyword(s):  
Discrimination Performance ◽  
Forced Choice ◽  
Forced Choice Tasks ◽  
Choice Tasks

A common first-order time-to-contact based control of hand-closure initiation in catching and grasping

2012 ◽  
Vol 31 (3) ◽  
pp. 529-540 ◽  
Author(s):  
Cornelis van de Kamp ◽  
Raoul M. Bongers ◽  
Frank T.J.M. Zaal
Keyword(s):  
Time To Contact ◽  
First Order

scholarly journals Spatial Estimation of Accelerated Stimuli Is Based on a Linear Extrapolation of First-Order Information

2016 ◽  
Vol 63 (2) ◽  
pp. 98-106 ◽  
Author(s):  
Simon J. Bennett ◽  
Nicolas Benguigui
Keyword(s):  
Estimation Error ◽  
Spatial Prediction ◽  
Object Motion ◽  
Spatial Estimation ◽  
First Order ◽  
Temporal Prediction ◽  
Prediction Motion ◽  
Negative Acceleration ◽  
Positive Acceleration ◽  
Individual Participant

Abstract. We examined spatial estimation of accelerating objects (−8, −4, 0, +4, or +8 deg/s2) during occlusion (600, 1,000 ms) in a spatial prediction motion task. Multiple logistic regression indicated spatial estimation was influenced by these factors such that participants estimated objects with positive acceleration to reappear behind less often than those with negative acceleration, and particularly after the longer occlusion. Individual-participant logistic regressions indicated spatial estimation was better predicted by a first-order extrapolation of the occluded object motion based on pre-occlusion velocity rather than a second-order extrapolation that took account of object acceleration. We suggest a general principle of extrapolation is involved in prediction motion tasks whereby there is a contraction of the variable of interest (i.e., displacement in spatial prediction motion and time in temporal prediction motion). Such an approach to extrapolation could be advantageous as it would offer participants better opportunity to correct for an initial estimation error.

scholarly journals VISUAL CONTROL OF VELOCITY OF APPROACH BY PIGEONS WHEN LANDING

1993 ◽  
Vol 180 (1) ◽  
pp. 85-104 ◽  
Author(s):  
D. N. Lee ◽  
M. N. O. Davies ◽  
P. R. Green ◽  
F. R. (Ruud). Van Der Weel
Keyword(s):  
Binocular Vision ◽  
Order Approximation ◽  
Threshold Value ◽  
Visual Control ◽  
Rate Of Change ◽  
Neural Computation ◽  
Time To Contact ◽  
Tau Function ◽  
First Order ◽  
First Order Approximation

Films of pigeons flying to a perch were analysed to test a theory of how speed of approach and timing of foot extension in preparation for landing are visually controlled. Rapid neural computation of distance to perch and of speed and deceleration would seem to be required. However, according to the theory, none of this is necessary. Simpler control is possible based solely on the value of the tau function of certain optic variables x, where the tau function of × is × divided by its rate of change; i.e. tau(x)=x/x˙˙ tau(x) is a first-order approximation of time to contact with the perch and so could be used for timing foot extension. Controlled braking is possible by simply keeping tau(x), the rate of change of tau(x), constant. The results indicated that pigeons did regulate their braking when approaching the perch by keeping tau(x) constant and initiated foot extension when tau(x) reached a threshold value of approximately 150 ms. They followed this procedure even when they had one eye covered, and so binocular vision was not necessary for regulating braking or timing foot extension. It is shown that an optic variable that the pigeons could be using is the width of the optic projection of the gap between foot and perch. It is further shown that they could be using the same optic variable for controlling the trajectory of their feet to contact the perch.

scholarly journals Coming in, or going out? Measuring the effect of discourse factors on perspective prominence

2021 ◽  
Vol 1 ◽  
pp. 1
Author(s):  
Carolyn Jane Anderson
Keyword(s):  
Common Property ◽  
American English ◽  
Choice Experiments ◽  
Forced Choice ◽  
Motion Verbs ◽  
Diverse Group ◽  
Global And Local

Although perspectival expressions are a diverse group, they share a common property: their meanings depend on the perspective of a discourse-given individual whose identity is under-specified. This paper investigates how perspective holder prominence is determined through a series of forced choice experiments on American English motion verbs exploring a number of discourse factors: definiteness, mention order, topicality, and subjecthood. The results suggest that both global and local prominence effects play a role in determining how perspectival motion verbs are interpreted.

A Pedestal Blocks the Perception of Non-Fourier Motion

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 17-17 ◽  
Author(s):  
O I Ukkonen ◽  
A M Derrington
Keyword(s):  
Modulation Depth ◽  
Discrimination Performance ◽  
Spatial Variations ◽  
Second Order ◽  
First Order ◽  
Direction Discrimination ◽  
Forced Choice Task ◽  
The Mean ◽  
Texture Contrast ◽  
Moving Pattern

We wanted to know whether the mechanisms that discriminate the motion of first-order patterns (defined by spatial variations of luminance) differ from those that detect the motion of non-Fourier or second-order patterns (defined by spatial variations of contrast). To address this question we tested whether motion discrimination performance of first-order and second-order patterns was affected by a pedestal (Lu and Sperling, 1995 Vision Research35 2697 – 2722). A pedestal is a static replica of a moving pattern. We used pedestals with contrast or modulation depth twice the value at which it becomes possible to discriminate the direction of a moving pattern. A two-interval forced-choice task was used to determine how direction discrimination varies with contrast of sine gratings (1 cycle deg−1) and modulation depth of amplitude-modulated gratings presented either alone or with a pedestal. The amplitude-modulated gratings had a 5 cycles deg−1 carrier modulated at 1 cycle deg−1. Three different temporal frequencies (1, 3, and 12 Hz) were studied. Performance with sine gratings was unaffected by the pedestal at all temporal frequencies tested. For amplitude-modulated gratings the pedestal raised the modulation depth at which it became possible to discriminate the direction of motion. This elevation in threshold decreased when the mean contrast of the pattern was high. This result shows that immunity to pedestals of texture-contrast patterns (Lu and Sperling, 1996 Journal of the Optical Society of America13 2305 – 2318) does not generalise to other non-Fourier motion stimuli.

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