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For orientation contrast, there is no specific adaptation angle, i.e., the network has developed in an environment of all possible angles. In this case, when the surround is of angle , the network response to a stimulus of angle is
in which and has the same meaning as for orientation adaptation. Again assuming the maximum likelihood, , the stimulus angle at which it is perceived as angle 0, is derived and shown in figure 5 (left). The solid line is the theoretical curve and the experimental data come from  and their estimated error is . The parameter obtained through fit is the strength of decorrelation feedback: .
We can derive the peak position , i.e., the surrounding angle at which the orientation contrast is most significant,
For , one immediately gets . This is in good agreement with experiments, most people experience the maximum effect of orientation contrast around this angle.
Our theory predicts that the peak position of the surround angle for orientation contrast should be constant since the orientation tuning width is roughly the same for different human observers and is not going to change much for different experimental setups. But the peak value of the perceived angle is not constant since the decorrelation feedback parameter is not necessarily same, indeed, it could be quite different for different human observers and different experimental setups.