The puncta were identified based on having a fluorescence intensity that exceeded a threshold set by a blind observer to maximize discrimination of puncta from the background, and a diameter between 0.5 and 5 µm.
To control for a potential confound between physical similarity and gender, we used a Bayesian ideal observer and human discrimination data to construct a stimulus set in which pairs of different-gender faces were equally dissimilar as same-gender pairs.
Firstly, we wanted the perceptual judgment to target specifically the visibility of the motion stimulus (type I task: judging an external event [19]) rather than the confidence of the observer's own discrimination response (type II task: judging an internal event): Being confident of the response is not equivalent of being aware of the stimulus [20].
This approach exploits additivity of variance, whereby internal noise and external noise contribute independently to an observer's direction discrimination threshold.
Manchester City midfielder Toure, who suffered racist abuse at CSKA Moscow last season, was speaking as Fifa launched a system where match observers will monitor discrimination incidents.
In perceptual learning, observers improve their discrimination or detection performance in perceptual tasks through repeated practice or training [5], [6], [7], [8], [9], [10], [11], [12].
As proposed by Chung et al. (2002), who also found an upward shift in SF tuning for humans as compared to the ideal observer in a letter discrimination task, the SF tuning estimate for humans likely reflects both the diagnostic information in the stimulus as well as physiological properties of the visual system.
Norman et al. (2003), for example, found that their older observers' thresholds for speed discrimination were, on average, 58.7percentt higher than those of the younger observers.
It's not just that it might happen but that it happens very often," said the Sova Centre director, Alexander Verkhovsky, at a panel of Russian and foreign football observers last month to discuss discrimination in Russian football.
We found that as the size of the disparity increased, the magnitude of perceived depth increased, while the precision with which observers could make depth discrimination judgments decreased.
Observers performed four-choice discrimination of actions in three separate blocks of 200 trials.
