Fig. 4.
Results with human subjects. (A) Normalized accuracy of detecting a single target, shown for each type of background. Results with isotropic background represent observers' intrinsic bias for certain target orientation (in this case, horizontal). Even after accounting for this bias (applying a binomial test with hypothetical probabilities of success being estimated from trials with isotropic background), target detection on oriented background exhibits strong orientation saliency effect. *P < 10−5, binomial test. (B) Results of trials with two targets having the same orientation. Again, a strong saliency effect is observed, in full correspondence to the archer fish results. *P < 10−4, binomial test. (C) Detection error rates in trials with a single target presentation, broken down by background type. By depicting the probability of subjects to wrongfully report that no bar was presented, this plot shows that the accuracy drops drastically when the background is oriented compared with the baseline with isotropic background. *P < 10−10, binomial test. (D) Detection error rates in trials with two targets of different orientations. Results denote subjects’ probability to incorrectly report a single bar. Note how the accuracy is significantly reduced when the background is oriented compared with the baseline with isotropic background. *P < 10−10, binomial test. Considered together, the results in all these panels suggest a strong saliency effect for the incongruent target compared with the congruent one.