Anisotropic Temporal Integration in the Perception of Stereoscopic Corrugations

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 170-170 ◽  
Author(s):  
M R Hegarty ◽  
P B Hibbard ◽  
M F Bradshaw ◽  
B De Bruyn ◽  
A D Parton
Keyword(s):  
Linear Relationship ◽  
Stimulus Duration ◽  
Exposure Duration ◽  
Temporal Integration ◽  
Surface Orientation ◽  
Similar Relationship ◽  
Spatial Frequencies ◽  
Do So

Disparity sensitivity for horizontal depth corrugations increases with exposure duration for presentations of up to 1 s (Tyler, 1990 Vision Research30 1877 – 1895). To extend the work of Parton et al (1996 Perception25 67) we investigated whether differences existed in the effects of exposure for corrugations at different orientations. Disparity thresholds were measured for horizontal, vertical, and diagonal gratings with spatial frequencies ranging between 0.1 cycle deg−1 and 0.8 cycle deg−1, as a function of stimulus duration. Stimuli were presented for exposures of between 50 ms and 32 s, and were followed by a random disparity mask, which served the important function of disrupting further processing of stimulus disparity. Thresholds were greatest for vertical gratings. This effect was particularly pronounced for the lowest frequencies. In all conditions, disparity sensitivity improved as exposure duration increased, and continued to do so for all durations tested. For vertical and diagonal gratings, log - log plots of threshold against time showed a linear relationship with a slope of −1 up to 1.0 s, after which time improvements in sensitivity reduced. Horizontal gratings showed a similar relationship, but with thresholds ceasing to decrease significantly after 0.5 s. Temporal integration limits differ with surface orientation, and represent another important difference in our ability to detect and encode depth in stereoscopic surfaces.

Temporal Integration and the Masking Effect of Spatiotemporal Noise

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 216-216 ◽  
Author(s):  
H T Kukkonen ◽  
J Rovamo
Keyword(s):  
Spectral Density ◽  
Exposure Duration ◽  
Temporal Integration ◽  
Detection Threshold ◽  
Critical Duration ◽  
Masking Effect ◽  
Integration Time ◽  
Detection Thresholds ◽  
Spatial Noise ◽  
Spatiotemporal Noise

In computer-generated spatiotemporal noise every stimulus frame contains a new static noise sample. The spectral density of white spatiotemporal noise is calculated by multiplying the squared rms contrast of noise by the product of the noise check area and the exposure duration of each noise check. When the exposure duration of each noise check is gradually increased, the spectral density of spatiotemporal noise increases, reaching its maximum when noise becomes static. In static spatial noise both stimulus and noise checks have the same duration. The signal-to-noise ratio is known to be constant at detection threshold. Detection thresholds should thus increase in proportion to the spectral density of spatiotemporal noise, which increases with the duration of the noise checks. We measured detection thresholds for stationary cosine gratings embedded in spatiotemporal noise. The exposure duration of the noise checks was increased from one frame duration to the total exposure duration of the stimulus grating. Noise was thus gradually transformed from spatiotemporal to static spatial noise. The contrast energy threshold increased in proportion to the spectral density of spatiotemporal noise up to a noise check duration found to be equal to the integration time for the stimulus grating without noise. After this, energy thresholds remained constant in spite of the increase in the spectral density of spatiotemporal noise. This suggests that the masking effect of spatiotemporal noise increases with the duration of noise checks up to the critical duration marking the saturation of the temporal integration of the signal.

Perceptual and Electrophysiological Correlates of Fixed Versus Moving Sound Source Lateralization

2020 ◽  
Vol 63 (9) ◽  
pp. 3176-3194
Author(s):  
Barrett Victor St. George ◽  
Barbara Cone
Keyword(s):  
Stimulus Duration ◽  
Stimulus Type ◽  
Right Hemisphere ◽  
Temporal Integration ◽  
Perceptual Bias ◽  
P300 Amplitude ◽  
Hemispheric Dominance ◽  
Interaural Level Difference ◽  
Moving Targets ◽  
Fixed Type

Purpose The aims of the study were (a) to evaluate the effects of systematically varied factors of stimulus duration, interaural-level difference (ILD), and direction on perceptual and electrophysiological metrics of lateralization for fixed versus moving targets and (b) to evaluate the hemispheric activity underlying perception of fixed versus moving auditory targets. Method Twelve normal-hearing, young adult listeners were evaluated using perceptual and P300 tests of lateralization. Both perceptual and P300 tests utilized stimuli that varied for type (fixed and moving), direction (right and left), duration (100 and 500 ms), and magnitude of ILD (9 and 18 dB). Listeners provided laterality judgments and stimulus-type discrimination (fixed vs. moving) judgments for all combinations of acoustic factors. During P300 recordings, listeners discriminated between left- versus right-directed targets, as the other acoustic parameters were varied. Results ILD magnitude and stimulus type had statistically significant effects on laterality ratings, with larger magnitude ILDs and fixed type resulting in greater lateralization. Discriminability between fixed versus moving targets was dependent on stimulus duration and ILD magnitude. ILD magnitude was a significant predictor of P300 amplitude. There was a statistically significant inverse relationship between the perceived velocity of targets and P300 latency. Lateralized targets evoked contralateral hemispheric P300 activity. Moreover, a right-hemisphere enhancement was observed for fixed-type lateralized deviant stimuli. Conclusions Perceptual and P300 findings indicate that lateralization of auditory movement is highly dependent on temporal integration. Both the behavioral and physiological findings of this study suggest that moving auditory targets with ecologically valid velocities are processed by the central auditory nervous system within a window of temporal integration that is greater than that for fixed auditory targets. Furthermore, these findings lend support for a left hemispatial perceptual bias and right hemispheric dominance for spatial listening.

THE MICRO-CLIMATE OF FRUIT TREES: I. LIGHT MEASUREMENTS WITH URANYL OXALATE ACTINOMETERS

1963 ◽  
Vol 43 (4) ◽  
pp. 561-568 ◽  
Author(s):  
Don R. Heinicke
Keyword(s):  
Light Intensity ◽  
Oxalic Acid ◽  
Linear Relationship ◽  
Potassium Permanganate ◽  
Fruit Trees ◽  
Similar Relationship ◽  
Measuring Device ◽  
Uranyl Oxalate ◽  
Climate Studies

A light meter using uranyl oxalate actinometry has been developed for use in studies of tree micro-climate. The method is based on the photo-destruction of oxalic acid in the presence of uranyl sulphate. The total amount of oxalic acid destroyed is determined by titration with deci-normal potassium permanganate. A linear relationship between the actinometer readings and gm. cal. day−1 cm.−2, as recorded by an Eppley pyrheliometer, was shown on bright days. A similar relationship was shown with time of exposure at a fixed light intensity. In micro-climate studies many readings of integrated light values can be taken with this inexpensive light measuring device.

Planar surface orientation from texture spatial frequencies

1995 ◽  
Vol 28 (5) ◽  
pp. 729-743 ◽  
Author(s):  
Boaz J. Super ◽  
Alan C. Bovik
Keyword(s):  
Surface Orientation ◽  
Planar Surface ◽  
Spatial Frequencies

Kinetic Aspects of the Interaction of Blood-Clotting Enzymes

1967 ◽  
Vol 17 (03/04) ◽  
pp. 349-357 ◽  
Author(s):  
H. C Hemker ◽  
T Siepel ◽  
R Altman ◽  
E. A Loeliger
Keyword(s):  
Linear Relationship ◽  
Blood Clotting ◽  
Factor V ◽  
Similar Relationship ◽  
Factor X ◽  
Contact Activation ◽  
Clotting Time ◽  
Normal Plasma ◽  
Straight Line ◽  
Line Relationship

SummaryIt is demonstrated that clotting time in a thrombotest experiment bears a linear relationship to the inverse of factor X concentration under conditions in which the ratio of factor X to the factors II and VII is equal to or smaller than the ratio in normal plasma.A similar relationship occurs with other thromboplastins as long as factor V and fibrinogen are present in excess, i. e. when the dilutions are made with BaSO4 absorbed plasma.Contact activation causes deviation from the observed straight-line relationship.

Temporal Integration of Vibrotactile Stimulation

1967 ◽  
Vol 25 (2) ◽  
pp. 549-560 ◽  
Author(s):  
Birgitta Berglund ◽  
Ulf Berglund ◽  
Goesta Ekman
Keyword(s):  
Power Function ◽  
Stimulus Duration ◽  
Temporal Integration ◽  
Logarithmic Function ◽  
Vibrotactile Stimulation ◽  
Scaling Method ◽  
Perceived Intensity ◽  
Psychophysical Scaling

The perceived intensity of vibrotactile stimulation at 250 c/s was measured by a psychophysical scaling method under different conditions of intensity (32–54 db) and duration (30–1200 msec.) of stimulation. It was found (1) that perceived intensity grows as a logarithmic function of stimulus duration up to about 1 sec., whereafter it remains constant, and (2) that the exponent of the psychophysical power function decreases from 0.7 at the shortest duration and approaches a constant value of about 0.4 for the longest durations.

Stimulus Duration and Frequency Discrimination for Normal-Hearing and Hearing-Impaired Subjects

1984 ◽  
Vol 27 (2) ◽  
pp. 252-256 ◽  
Author(s):  
Joseph W. Hall ◽  
Elizabeth J. Wood
Keyword(s):  
Stimulus Duration ◽  
Temporal Integration ◽  
Detection Threshold ◽  
Frequency Discrimination ◽  
Normal Hearing ◽  
Hearing Impaired ◽  
Frequency Difference ◽  
Impaired Group ◽  
Overall Performance ◽  
Pure Tones

Frequency discrimination for 500- and 2000-Hz pure tones at durations of 5, 10, 20, 50, and 200 ms was determined for 10 normal-hearing and 10 cochlear-impaired listeners. Listeners from both groups demonstrated monotonic increases in frequency difference limens as stimulus duration decreased. The functions of the hearing-impaired listeners were parallel to those of the normal-hearing listeners for stimulus durations between 10 and 200 ms, but the overall performance of the hearing-impaired group was poorer than that of the normal-hearing group. The functions of many of the cochlear-impaired subjects were less steep than normal for the shortest durations tested (between 5 and l0 ms). There appeared to be no relation between temporal integration for frequency discrimination and temporal integration for detection threshold. The results are discussed in terms of processes of temporal integration and frequency selectivity.

Temporal Integration and Contrast Sensitivity in Foveal and Peripheral Vision

Perception ◽  
1984 ◽  
Vol 13 (6) ◽  
pp. 665-674 ◽  
Author(s):  
Jyrki Rovamo ◽  
Lea Leinonen ◽  
Pentti Laurinen ◽  
Veijo Virsu
Keyword(s):  
Visual Field ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Peripheral Vision ◽  
Temporal Integration ◽  
Photopic Vision ◽  
Spatiotemporal Information ◽  
Spatial Frequencies ◽  
Primary Determinant ◽  
Integration Improvement

Spatial contrast sensitivity functions and temporal integration functions for gratings with dark surrounds were measured at various eccentricities in photopic vision. Contrast sensitivity decreased with increasing eccentricity at all exposure durations and spatial frequencies tested. The decrease was faster at high than at low spatial frequencies, but similar at different exposure durations. When cortically similar stimulus conditions were produced at different eccentricities by M-scaling, contrast sensitivity became independent of visual field location at all exposure durations tested. The results support the view that in photopic vision spatiotemporal information processing is qualitatively similar across the visual field, and that quantitative differences result from retinotopical differences in ganglion cell sampling. For gratings of constant retinal area temporal integration (improvement of contrast sensitivity with increasing exposure duration) was more extensive at high than at low retinal spatial frequencies but independent of cortical spatial frequency and eccentricity. For M-scaled gratings temporal integration was more extensive at high than at low cortical spatial frequencies but independent of retinal spatial frequency and eccentricity. The results suggest that the primary determinant of temporal integration is not spatial frequency but grating value that is calculated as AF2 square cycles (cycle2), where A is grating area and F spatial frequency.

Contrast Constancy Revisited: The Perceived Contrast of Sinusoidal Gratings above Threshold

2015 ◽  
Vol 68 (2) ◽  
pp. 363-380 ◽  
Author(s):  
Wayne S. Smith
Keyword(s):  
Visual System ◽  
Contrast Sensitivity ◽  
Local Adaptation ◽  
Significant Role ◽  
Stimulus Duration ◽  
Human Visual System ◽  
Sensitivity Function ◽  
Contrast Sensitivity Function ◽  
Spatial Frequencies ◽  
Sinusoidal Gratings

The contrast sensitivity function of the human visual system, measured with sinusoidal luminance gratings, has an inverted U shape with a peak around 2–4 c/deg. Above threshold, it is thought that luminance gratings of equal physical contrasts but of distinguishably different spatial frequencies are all perceived as having similar contrasts, a phenomenon that has been termed contrast constancy. However, when suprathreshold contrast matches were measured for pairs of luminance gratings whose spatial frequencies were indistinguishable, the matching curves were not flat and followed a similar inverted U shape form as the contrast sensitivity function at threshold. It was therefore suggested that contrast constancy may only be revealed when matching the contrasts of clearly distinguishable spatial frequencies. Here, observers matched the perceived contrasts of suprathreshold luminance gratings of similar but visibly different spatial frequencies between 0.25 and 16 c/deg. The results show that, much like the contrast sensitivity function at threshold, observers are more sensitive to intermediate spatial frequencies (1–6 c/deg) than they are to either higher or to lower spatial frequencies. This tuning is evident when matching reference contrasts of 30–80%, implying a significant role in everyday vision. To demonstrate that these results were not due to local adaptation, the experiment was repeated with shorter stimulus duration, producing the same results. The extent of departure from contrast constancy found in the present study is compared to previously reported suprathreshold measurements. The results are also discussed with consideration to limitations with display apparatus such as monitor blur.

Holding replication studies to mainstream standards of evidence

2018 ◽  
Vol 41 ◽  
Author(s):  
Duane T. Wegener ◽  
Leandre R. Fabrigar
Keyword(s):  
Replication Studies ◽  
Replication Research ◽  
Standards Of Evidence ◽  
Do So

AbstractReplications can make theoretical contributions, but are unlikely to do so if their findings are open to multiple interpretations (especially violations of psychometric invariance). Thus, just as studies demonstrating novel effects are often expected to empirically evaluate competing explanations, replications should be held to similar standards. Unfortunately, this is rarely done, thereby undermining the value of replication research.

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