Motion Parallax, Relative Size, and Benussi Effect

1993 ◽  
Vol 76 (3_suppl) ◽  
pp. 1320-1322 ◽  
Author(s):  
Willard L. Brigner ◽  
James R. Deni
Keyword(s):  
Motion Parallax ◽  
Relative Size ◽  
Apparent Depth

Many observers perceive depth when a configuration of nonconcentric circles is rotated on a disc. While it has been suggested by a number of investigators that motion parallax has a role in generating this phenomenon, the supporting data are equivocal. The current study proposed that the ambiguity regarding the role of motion parallax may have arisen because there are contradictions between relative size cues and motion parallax cues in the configuration of rotating circles. However, with 17 undergraduate observers, apparent depth was no more reliably reported with consistent cues of motion parallax and relative size than when these cues were contradictory.

Apparent Depth with Retinal Image Motion of Expansion and Contraction Yoked to Head Movement

Perception ◽  
1998 ◽  
Vol 27 (8) ◽  
pp. 937-949 ◽  
Author(s):  
Takanao Yajima ◽  
Hiroyasu Ujike ◽  
Keiji Uchikawa
Keyword(s):  
Motion Parallax ◽  
Ccd Camera ◽  
Head Movements ◽  
Image Motion ◽  
Apparent Depth ◽  
Motion Cues ◽  
Relative Expansion ◽  
Retinal Image Motion ◽  
Self Motion

The two main questions addressed in this study were (a) what effect does yoking the relative expansion and contraction (EC) of retinal images to forward and backward head movements have on the resultant magnitude and stability of perceived depth, and (b) how does this relative EC image motion interact with the depth cues of motion parallax? Relative EC image motion was produced by moving a small CCD camera toward and away from the stimulus, two random-dot surfaces separated in depth, in synchrony with the observers' forward and backward head movements. Observers viewed the stimuli monocularly, on a helmet-mounted display, while moving their heads at various velocities, including zero velocity. The results showed that (a) the magnitude of perceived depth was smaller with smaller head velocities (<10 cm s−1), including the zero-head-velocity condition, than with a larger velocity (10 cm s−1), and (b) perceived depth, when motion parallax and the EC image motion cues were simultaneously presented, is equal to the greater of the two possible perceived depths produced from either of these two cues alone. The results suggested the role of nonvisual information of self-motion on perceiving depth.

scholarly journals Size-mediated, density-dependent cannibalism in the signal crayfish Pacifastacus leniusculus (Dana, 1852) (Decapoda, Astacidea), an invasive crayfish in Britain

Crustaceana ◽  
2017 ◽  
Vol 90 (4) ◽  
pp. 417-435 ◽  
Author(s):  
R. J. Houghton ◽  
C. Wood ◽  
X. Lambin
Keyword(s):  
Relative Size ◽  
Pacifastacus Leniusculus ◽  
Gut Contents ◽  
Size Distributions ◽  
Signal Crayfish ◽  
Density Dependent ◽  
Invasive Crayfish ◽  
The Relationship ◽  
Best Fit

The role of cannibalism in crayfish populations is not well understood, despite being a potentially key density-dependent process underpinning population dynamics. We studied the incidence of cannibalism in an introduced signal crayfish Pacifastacus leniusculus population in a Scottish lowland river in September 2014. Animals were sampled using six different sampling techniques simultaneously, revealing variable densities and size distributions across the site. Cannibalism prevalence was estimated by analysing the gut contents of crayfish >20 mm CL for the presence of crayfish fragments, which was found to be 20% of dissected individuals. When seeking evidence of relationships between the sizes of cannibals and ‘prey’, the density of conspecifics <56% the size of a dissected individual yielded the best fit. The relationship between cannibalism probability and crayfish size and density was equally well described by three different metrics of crayfish density. Cannibalism increased with crayfish size and density but did not vary according to sex. These results suggest that large P. leniusculus frequently cannibalize smaller (prey) conspecifics, and that the probability of cannibalism is dependent upon the relative size of cannibal-to-prey and the density of the smaller crayfish. We suggest that removing large individuals, as targeted by many traditional removal techniques, may lead to reduced cannibalism and therefore a compensatory increase in juvenile survival.

scholarly journals The role of motion parallax in the perception of egocentric direction

2017 ◽  
Vol 17 (10) ◽  
pp. 985
Author(s):  
Kait Clark ◽  
Simon Rushton
Keyword(s):  
Motion Parallax ◽  
Egocentric Direction

scholarly journals Differences in acid phosphomonoesterase activity in forest soils of the Smrk Massive in the Moravskoslezské Beskydy Mts. (Czech Republic)

Beskydy ◽  
2012 ◽  
Vol 5 (2) ◽  
pp. 135-152
Author(s):  
A. Bajer ◽  
P. Samec ◽  
M. Žárník
Keyword(s):  
Relative Size ◽  
Chemical Properties ◽  
Principal Component ◽  
European Beech ◽  
Soil Characteristics ◽  
Strong Correlations ◽  
Spruce Stands ◽  
The Individual ◽  
A Site

The purpose of this paper is to determine the individual relations between APEA and specific soils and environmental factors. To disclose these relations, analysis of component vectors and principal component analysis (PCA) were performed. Vectors of soil characteristics with participation of APEA (aAKFE) and vectors of pedochemical variables (aCHEM) were also calculated. Their ratio (ia) indicated the relative size of the APEA impact on the relations between pedochemical characteristics. Based on the statistical analyses, different role of APEA in Norway spruce and in European beech stands was detected. While APEA in spruce stands did not show significant correlations with the other examined soil chemical properties, soils under beech stands displayed strong correlations with some of the pedochemical variables. The idea of this research is to find out whether APEA could be used as an indicator of forest vegetation status and of the anthropogenic load on a site.

The Role of Figure Orientation and Apparent Depth in the Perception of the Horizontal—Vertical Illusion

Perception ◽  
1975 ◽  
Vol 4 (1) ◽  
pp. 79-83 ◽  
Author(s):  
Harvey R Schiffman ◽  
Jack G Thompson
Keyword(s):  
Stimulus Figure ◽  
Vertical Line ◽  
Apparent Depth ◽  
Horizontal Line ◽  
Size Constancy ◽  
Illusory Effect

An experiment was performed which examined the role of figural orientation directly, and the role of an inappropriately invoked size-constancy mechanism indirectly, in the actuation and magnitude of the horizontal—vertical illusion. When the vertical line of the stimulus figure was aligned above the horizontal line, the illusory effect was significant and positive; in contrast, when the vertical line was located below the horizontal line, the illusion was negative. Under the assumption that a vertical line can appear as a foreshortened line in depth, these findings support an explanation based on the operation of a misapplied size-constancy mechanism.

The Familiar-Size Cue to Depth under Reduced-Cue Viewing Conditions

Perception ◽  
1994 ◽  
Vol 23 (11) ◽  
pp. 1301-1312 ◽  
Author(s):  
John Predebon ◽  
Jacob Steven Woolley
Keyword(s):  
Motion Parallax ◽  
Verbal Report ◽  
Major Determinant ◽  
Relative Distance ◽  
Head Motion ◽  
Familiar Size ◽  
Verbal Reports ◽  
Direct Reports ◽  
Visual Conditions

The familiar-size cue to perceived depth was investigated in five experiments. The stimuli were stationary familiar objects viewed monocularly under otherwise completely darkened visual conditions. Perceived depth was measured directly with the method of verbal report and indirectly with the head-motion procedure. Although the familiar-size cue influenced verbal reports of the distances of the objects, it did not determine perceived depth as assessed with the head-motion procedure. These findings support the claim that familiar size is not a major determinant of perceived depth, and that cognitive or nonperceptual factors mediate the effects of familiar size on direct reports of depth and distance. Possible reasons for the failure of familiar size to influence the head-motion-derived measures of perceived depth are discussed with particular emphasis on the role of motion parallax in determining perceptions of depth and relative distance.

The effect of overall stimulus velocity on motion parallax

2008 ◽  
Vol 25 (1) ◽  
pp. 3-15 ◽  
Author(s):  
YING ZHANG ◽  
PETER H. SCHILLER
Keyword(s):  
Motion Parallax ◽  
Three Dimensional ◽  
Reaction Times ◽  
Visual Display ◽  
Stimulus Movement ◽  
Stimulus Velocity ◽  
Target Region ◽  
Performance Accuracy ◽  
Dimensional Object

This study examined the effectiveness with which motion parallax information can be utilized by rhesus monkeys for depth perception. A visual display comprised of random-dots that mimicked a rigid, three-dimensional object rocking back and forth was used. Differential depth was produced by presenting sub-regions of the dots moving at different velocities from the rest of dots in the display. The tasks for the monkeys were to detect or discriminate a target region that was protruding the furthest from the background plane. To understand the role of stimulus movement, we examined the accuracy and the rapidity of the saccadic responses as a function of rocking velocity of the entire three-dimensional object. The results showed that performance accuracy improved and reaction times decreased with increasing rocking velocities. The monkeys can process the motion parallax information with remarkable rapidity such that the average reaction time ranged between 212 and 246 milliseconds. The data collected suggest that the successive activation of just two sets of cones is sufficient to perform the task.

The Information Intermediary Role of Short Sellers

2005 ◽  
Vol 80 (3) ◽  
pp. 941-966 ◽  
Author(s):  
Grace Pownall ◽  
Paul J. Simko
Keyword(s):  
Relative Size ◽  
Analyst Following ◽  
Earnings Expectations ◽  
Short Sellers ◽  
Future Performance ◽  
Information Intermediaries ◽  
Intermediary Role ◽  
Short Interest ◽  
Alternative Sources

This paper examines the conditions under which the market responds to disclosures of significant increases in short selling, and whether proxies for earnings expectations and alternative information sources help explain this response. Our sample is based on firms that experience abnormal short interest increases (“short spikes”) during 1989–1998. We find that the mean abnormal return around short spike announcements is significantly more negative for firms with low analyst following, consistent with short sellers providing perceived value when there are limited alternative sources of guidance available. For firms with high analyst following we find the market response is dependent on earnings levels, consistent with investors viewing a short interest increase as providing information about the sustainability of earnings. Additional analyses reveal that these inferences are not affected by measures of firms' earnings quality or by the relative size of the short spike. We infer from our analyses that the information content of short interest disclosures is conditional on both the firms' existing information environment and expectations of future performance as conveyed by prior earnings. This inference is consistent with short sellers' role as information intermediaries covering the lower tail of earnings expectations.

scholarly journals The Role of Clustering in the Adoption of Organic Dairy: A Longitudinal Networks Analysis between 2002 and 2015

2019 ◽  
Vol 11 (6) ◽  
pp. 1514 ◽  
Author(s):  
Juan Sánchez Herrera ◽  
Carolyn Dimitri
Keyword(s):  
Relative Size ◽  
Dairy Farm ◽  
Organic Production ◽  
Market Development ◽  
Temporal Networks ◽  
Organic Dairy ◽  
The Usa ◽  
Networks Analysis ◽  
Spatio Temporal

This paper uses network analysis to study the geo-localization decisions of new organic dairy farm operations in the USA between 2002 and 2015. Given a dataset of organic dairy certifications we simulated spatio-temporal networks based on the location of existing and new organic dairy farming operations. The simulations were performed with different probabilities of connecting with existing or incoming organic farmer operations, to overcome the lack of data describing actual connections between farmers. Calculated network statistics on the simulated networks included the average degree, average shortest path, closeness (centrality), clustering coefficients, and the relative size of the largest cluster, to demonstrate how the networks evolved over time. The findings revealed that new organic dairy operations cluster around existing ones, reflecting the role of networks in the conversion into organic production. The contributions of this paper are twofold. First, we contribute to the literature on clustering, information sharing, and market development in the agri-food industry by analyzing the potential implications of social networking in the development of a relatively new agriculture market. Second, we add to the literature on empirical social networks by using a new dataset with information on actors not previously studied analytically.

Stopping Super-Earths from growing into Jupiters

2020 ◽  
Author(s):  
Mohamad Ali-Dib ◽  
Andrew Cumming ◽  
Doug Lin
Keyword(s):  
Planet Formation ◽  
Thermal State ◽  
Relative Size ◽  
Protoplanetary Disk ◽  
Outer Envelope ◽  
Dominant Type ◽  
Lower Entropy ◽  
Gas Accretion ◽  
The Hill

&lt;p&gt;Super-Earths are by far the most dominant type of exoplanet, yet their formation is&lt;br /&gt;still not well understood. In particular, planet formation models predict that many&lt;br /&gt;of them should have accreted enough gas to become gas giants. Here we examine the&lt;br /&gt;role of the protoplanetary disk in the cooling and contraction of the protoplanetary&lt;br /&gt;envelope. In particular, we investigate the effects of 1) the thermal state of the disk as&lt;br /&gt;set by the relative size of heating by accretion or irradiation, and whether its energy is&lt;br /&gt;transported by radiation or convection, and 2) advection of entropy into the outer envelope by disk flows that penetrate the Hill sphere, as found in 3D global simulations.&lt;br /&gt;We find that, at 0.1 AU, the envelope quickly becomes fully radiative, nearly isothermal, and thus cannot cool down, stalling gas accretion. This&lt;br /&gt;effect is significantly more pronounced in convective disks, leading to envelope mass or-&lt;br /&gt;ders of magnitude lower. Entropy advection at 0.1 AU in either radiative or convective&lt;br /&gt;disks could therefore explain why super-Earths failed to undergo runaway accretion.&lt;/p&gt; &lt;p&gt;Ali-Dib, Cumming, &amp; Lin (MNRAS 2020)&lt;/p&gt;

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