Geometry in Visual Space—Some Method-Dependent (Arti)Facts

Perception ◽  
1977 ◽  
Vol 6 (6) ◽  
pp. 657-660 ◽  
Author(s):  
Walter H Ehrenstein
Keyword(s):  
Scalar Curvature ◽  
Visual Space ◽  
Simultaneous Comparison ◽  
Absolute Judgement

The measure of scalar curvature K varies with the method used to determine it. Overconstancy is found only with simultaneous comparison, nearly perfect constancy results from successive judgement, while absolute judgement produces underconstancy.

Response and Reinforcement in Operant Audiometry

1987 ◽  
Vol 52 (3) ◽  
pp. 294-299 ◽  
Author(s):  
Michael A. Primus
Keyword(s):  
Operant Conditioning ◽  
Space Versus ◽  
Visual Space ◽  
Central Processing ◽  
Operant Discrimination ◽  
Conditioning Rate ◽  
Significant Difference ◽  
Simple Detection ◽  
Variable Success ◽  
Response Task

Variable success in audiometric assessment of young children with operant conditioning indicates the need for systematic examination of commonly employed techniques. The current study investigated response and reinforcement features of two operant discrimination paradigms with normal I7-month-old children. Findings indicated more responses prior to the onset of habituation when the response task was based on complex central processing skills (localization and coordination of auditory/visual space) versus simple detection. Use of animation in toy reinforcers resulted in more than a twofold increase in the number of subject responses. Results showed no significant difference in response conditioning rate or consistency for the response tasks and forms of reinforcement examined.

Editorial: Human motion perception, eye movements, and orientation in visual space

2000 ◽  
Vol 59 (2) ◽  
pp. 85-88 ◽  
Author(s):  
Rudolf Groner ◽  
Marina T. Groner ◽  
Kazuo Koga
Keyword(s):  
Eye Movements ◽  
Motion Perception ◽  
Visual Space ◽  
Human Motion

Focusing of Visuospatial Attention

2001 ◽  
Vol 15 (4) ◽  
pp. 256-274 ◽  
Author(s):  
Caterina Pesce ◽  
Rainer Bösel
Keyword(s):  
Reaction Times ◽  
Visual Space ◽  
Spatial Relation ◽  
Stimulus Onset ◽  
Visuospatial Attention ◽  
Task Demands ◽  
Time Interval ◽  
Behavioral Studies ◽  
Task Conditions ◽  
Simple Rt

Abstract In the present study we explored the focusing of visuospatial attention in subjects practicing and not practicing activities with high attentional demands. Similar to the studies of Castiello and Umiltà (e. g., 1990) , our experimental procedure was a variation of Posner's (1980) basic paradigm for exploring covert orienting of visuospatial attention. In a simple RT-task, a peripheral cue of varying size was presented unilaterally or bilaterally from a central fixation point and followed by a target at different stimulus-onset-asynchronies (SOAs). The target could occur validly inside the cue or invalidly outside the cue with varying spatial relation to its boundary. Event-related brain potentials (ERPs) and reaction times (RTs) were recorded to target stimuli under the different task conditions. RT and ERP findings showed converging aspects as well as dissociations. Electrophysiological results revealed an amplitude modulation of the ERPs in the early and late Nd time interval at both anterior and posterior scalp sites, which seems to be related to the effects of peripheral informative cues as well as to the attentional expertise. Results were: (1) shorter latency effects confirm the positive-going amplitude enhancement elicited by unilateral peripheral cues and strengthen the criticism against the neutrality of spatially nonpredictive peripheral cueing of all possible target locations which is often presumed in behavioral studies. (2) Longer latency effects show that subjects with attentional expertise modulate the distribution of the attentional resources in the visual space differently than nonexperienced subjects. Skilled practice may lead to minimizing attentional costs by automatizing the use of a span of attention that is adapted to the most frequent task demands and endogenously increases the allocation of resources to cope with less usual attending conditions.

Sources of Variability in Dose Response Platelet Aggregometry

1985 ◽  
Vol 53 (02) ◽  
pp. 219-220 ◽  
Author(s):  
M V Vickers ◽  
S G Thompson
Keyword(s):  
Dose Response ◽  
Maximum Velocity ◽  
Adenosine Diphosphate ◽  
Method Error ◽  
Platelet Aggregability ◽  
Differential Effects ◽  
Platelet Aggregometry ◽  
Simultaneous Comparison ◽  
Aggregation Parameters ◽  
Very High

SummaryAn experiment designed to assess the components of variability of a number of measures of platelet aggregability showed that the ADP ED50 (the estimated dose of adenosine diphosphate at which primary aggregation occurs at half its maximum velocity) had the least method error of any of the parameters measured, but that none had a very high between-person component of variability. A simultaneous comparison of a syringe technique and a free-flowing technique for venepuncture revealed no differential effects on the aggregation parameters measured. An enforced increase in the stirring speed in the aggregometer led to an experiment which showed that such a change did not apparently affect the ED50s.

Spatial suppression due to statistical regularities is driven by distractor suppression not by target activation

2018 ◽  
Author(s):  
Michel Failing ◽  
Benchi Wang ◽  
Jan Theeuwes
Keyword(s):  
High Probability ◽  
Target Location ◽  
Target Selection ◽  
Visual Space ◽  
Alternative Interpretation ◽  
Distractor Location ◽  
Target Presentation ◽  
Statistical Regularities ◽  
Low Probability ◽  
Presentation Experiment

Where and what we attend to is not only determined by what we are currently looking for but also by what we have encountered in the past. Recent studies suggest that biasing the probability by which distractors appear at locations in visual space may lead to attentional suppression of high probability distractor locations which effectively reduces capture by a distractor but also impairs target selection at this location. However, in many of these studies introducing a high probability distractor location was tantamount to increasing the probability of the target appearing in any of the other locations (i.e. the low probability distractor locations). Here, we investigate an alternative interpretation of previous findings according to which attentional selection at high probability distractor locations is not suppressed. Instead, selection at low probability distractor locations is facilitated. In two visual search tasks, we found no evidence for this hypothesis: neither when there was only a bias in target presentation but no bias in distractor presentation (Experiment 1), nor when there was only a bias in distractor presentation but no bias in target presentation (Experiment 2). We conclude that recurrent presentation of a distractor in a specific location leads to attentional suppression of that location through a mechanism that is unaffected by any regularities regarding the target location.

Positive scalar curvature metrics via end-periodic manifolds

2020 ◽  
Vol 5 (3) ◽  
pp. 639-676
Author(s):  
Michael Hallam ◽  
Varghese Mathai
Keyword(s):  
Scalar Curvature ◽  
Positive Scalar Curvature ◽  
Positive Scalar

scholarly journals On the quantization of folded strings in non-critical dimensions

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jacob Sonnenschein ◽  
Dorin Weissman
Keyword(s):  
Scalar Curvature ◽  
Space Dimension ◽  
Massive Particle ◽  
Open String ◽  
Closed String ◽  
Target Space ◽  
Critical Dimensions ◽  
Complete Set ◽  
Rotating String ◽  
Folding Point

Abstract Classical rotating closed string are folded strings. At the folding points the scalar curvature associated with the induced metric diverges. As a consequence one cannot properly quantize the fluctuations around the classical solution since there is no complete set of normalizable eigenmodes. Furthermore in the non-critical effective string action of Polchinski and Strominger, there is a divergence associated with the folds. We overcome this obstacle by putting a massive particle at each folding point which can be used as a regulator. Using this method we compute the spectrum of quantum fluctuations around the rotating string and the intercept of the leading Regge trajectory. The results we find are that the intercepts are a = 1 and a = 2 for the open and closed string respectively, independent of the target space dimension. We argue that in generic theories with an effective string description, one can expect corrections from finite masses associated with either the endpoints of an open string or the folding points on a closed string. We compute explicitly the corrections in the presence of these masses.

scholarly journals Quaternionic contact 4n + 3-manifolds and their 4n-quotients

2021 ◽  
Author(s):  
Yoshinobu Kamishima
Keyword(s):  
Scalar Curvature ◽  
Lie Group ◽  
Contact Structure ◽  
Einstein Manifolds ◽  
Hermitian Metrics ◽  
Kähler Metric ◽  
Formula One ◽  
Quaternion Space ◽  
Kahler Metric ◽  
Do So

AbstractWe study some types of qc-Einstein manifolds with zero qc-scalar curvature introduced by S. Ivanov and D. Vassilev. Secondly, we shall construct a family of quaternionic Hermitian metrics $$(g_a,\{J_\alpha \}_{\alpha =1}^3)$$ ( g a , { J α } α = 1 3 ) on the domain Y of the standard quaternion space $${\mathbb {H}}^n$$ H n one of which, say $$(g_a,J_1)$$ ( g a , J 1 ) is a Bochner flat Kähler metric. To do so, we deform conformally the standard quaternionic contact structure on the domain X of the quaternionic Heisenberg Lie group$${{\mathcal {M}}}$$ M to obtain quaternionic Hermitian metrics on the quotient Y of X by $${\mathbb {R}}^3$$ R 3 .

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