scholarly journals Interaction of contexts in context-dependent orientation estimation

2019 ◽  
Author(s):  
Ron Dekel ◽  
Dov Sagi
Keyword(s):  
Visual Processing ◽  
Combined Effect ◽  
List Type ◽  
Contextual Influences ◽  
Tilt Aftereffect ◽  
Tilt Illusion ◽  
Contextual Influence ◽  
Non Linear ◽  
Selection For ◽  
Visual History

AbstractThe processing of a visual stimulus is known to be influenced by the statistics in recent visual history and by the stimulus’ visual surround. Such contextual influences lead to perceptually salient phenomena, such as the tilt aftereffect and the tilt illusion. Despite much research on the influence of an isolated context, it is not clear how multiple, possibly competing sources of contextual influence interact. Here, using psychophysical methods, we compared the combined influence of multiple contexts to the sum of the isolated context influences. The results showed large deviations from linear additivity for adjacent or overlapping contexts, and remarkably, clear additivity when the contexts were sufficiently separated. Specifically, for adjacent or overlapping contexts, the combined effect was often lower than the sum of the isolated component effects (sub-additivity), or was more influenced by one component than another (selection). For contexts that were separated in time (600 ms), the combined effect measured the exact sum of the isolated component effects (in degrees of bias). Overall, the results imply an initial compressive transformation during visual processing, followed by selection between the processed parts.HighlightsNon-linear sub-additivity for increased context area or contrastNon-linear selection between overlapping or adjacent, dissimilar contextsLinear additivity for combinations of temporally separated contexts

scholarly journals A decision-time account of individual variability in context-dependent orientation estimation

2019 ◽  
Author(s):  
Ron Dekel ◽  
Dov Sagi
Keyword(s):  
Decision Making ◽  
Visual Processing ◽  
Initial Conditions ◽  
Decision Time ◽  
Individual Variability ◽  
Perceptual Bias ◽  
Large Individual ◽  
List Type ◽  
Tilt Aftereffect ◽  
Context Dependent

AbstractFollowing exposure to an oriented stimulus, the perceived orientation is slightly shifted, a phenomenon termed the tilt aftereffect (TAE). This estimation bias, as well as other context-dependent biases, is speculated to reflect statistical mechanisms of inference that optimize visual processing. Importantly, although measured biases are extremely robust in the population, the magnitude of individual bias can be extremely variable. For example, measuring different individuals may result in TAE magnitudes that differ by a factor of 5. Such findings appear to challenge the accounts of bias in terms of learned statistics: is inference so different across individuals? Here, we found that a strong correlation exists between reaction time and TAE, with slower individuals having much less TAE. In the tilt illusion, the spatial analogue of the TAE, we found a similar, though weaker, correlation. These findings can be explained by a theory predicting that bias, caused by a change in the initial conditions of evidence accumulation (e.g., prior), decreases with decision time (Dekel & Sagi, 2019b). We contend that the context-dependence of visual processing is more homogeneous in the population than was previously thought, with the measured variability of perceptual bias explained, at least in part, by the flexibility of decision-making. Homogeneity in processing might reflect the similarity of the learned statistics.HighlightsThe tilt aftereffect (TAE) exhibits large individual differences.Reduced TAE magnitudes are found in slower individuals.Reduced TAE in slower decisions can be explained by the reduced influence of prior.Therefore, individual variability can reflect decision making flexibility.

scholarly journals Does agricultural intensification cause tipping points in ecosystem services?

2021 ◽  
Author(s):  
Stephen C. L. Watson ◽  
Adrian C. Newton ◽  
Lucy E. Ridding ◽  
Paul M. Evans ◽  
Steven Brand ◽  
...  
Keyword(s):  
Ecosystem Services ◽  
Agricultural Intensification ◽  
Spatial Dynamics ◽  
Policy Option ◽  
List Type ◽  
Tipping Points ◽  
Software Models ◽  
Non Linear ◽  
Study Interval ◽  
The Impact

Abstract Context Agricultural intensification is being widely pursued as a policy option to improve food security and human development. Yet, there is a need to understand the impact of agricultural intensification on the provision of multiple ecosystem services, and to evaluate the possible occurrence of tipping points. Objectives To quantify and assess the long-term spatial dynamics of ecosystem service (ES) provision in a landscape undergoing agricultural intensification at four time points 1930, 1950, 1980 and 2015. Determine if thresholds or tipping points in ES provision may have occurred and if there are any detectable impacts on economic development and employment. Methods We used the InVEST suite of software models together with a time series of historical land cover maps and an Input–Output model to evaluate these dynamics over an 85-year period in the county of Dorset, southern England. Results Results indicated that trends in ES were often non-linear, highlighting the potential for abrupt changes in ES provision to occur in response to slight changes in underlying drivers. Despite the fluctuations in provision of different ES, overall economic activity increased almost linearly during the study interval, in line with the increase in agricultural productivity. Conclusions Such non-linear thresholds in ES will need to be avoided in the future by approaches aiming to deliver sustainable agricultural intensification. A number of positive feedback mechanisms are identified that suggest these thresholds could be considered as tipping points. However, further research into these feedbacks is required to fully determine the occurrence of tipping points in agricultural systems.

Time step selection for 6-noded non-linear joint element in elasto-viscoplasticity analyses

1990 ◽  
Vol 10 (1) ◽  
pp. 33-58 ◽  
Author(s):  
Koji Sekiguchi ◽  
R.Kerry Rowe ◽  
Kwan Yee Lo
Keyword(s):  
Time Step ◽  
Non Linear ◽  
Joint Element ◽  
Selection For ◽  
Step Selection

Effect of fitting sheep covers and injection of a mineral supplement on the brightness, clean colour and photostability of wool grown by grazing Merino sheep

2016 ◽  
Vol 56 (1) ◽  
pp. 18
Author(s):  
S. Hatcher ◽  
J. W. V. Preston
Keyword(s):  
Factorial Design ◽  
Genetic Resource ◽  
New South ◽  
Genetic Selection ◽  
Combined Effect ◽  
Mineral Supplement ◽  
Merino Sheep ◽  
Treatment Groups ◽  
South Wales ◽  
Selection For

Wethers sourced from a Merino genetic resource flock, selected on the basis of their measured wool clean colour at 2 years of age, were stratified on the basis of clean colour and allocated to one of four treatment groups in a 2 × 2 factorial design. The aim was to investigate the effect of coating the fleece and administration of a commercial mineral supplement on brightness, clean colour and photostability over a 12-month period when run on the Central Tablelands of New South Wales. Coating the fleece significantly improved both the brightness and clean colour of the fleece (P<0.001, by 4 and 0.5 T units, respectively), but had no effect on the photostability of the two traits. The mineral supplement had no significant impact on the colour or photostability traits and there was no evidence of an interaction between coating the fleece and the mineral supplement. Although the improvements in brightness and colour arising from coating the fleece complemented the predicted responses to genetic selection for these two traits, the combined effect would not be sufficient to replace the routine use of oxidative bleaching during processing.

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