Interocular suppression of a half-occluded region of stereoscopic images

We assessed the detectability d' of a monocular small gray dot target presented on a half-occluded region of stereoscopic three-dimensional background images by comparing it with that on a two-dimensional (2D) region. For our experiments we used a typical two-alternative temporal forced-choice procedure, in which the target was presented in one of two temporal intervals for approximately 67 ms, and observers selected the interval they believed to have contained the target by pressing the corresponding key. To vary target signal intensity, we changed the target contrast against the background. According to signal-detection theory, we converted the percent-correct data to detectability d' and found that the relationship between d' and the contrast of the target followed Legge's equation. We used Legge's equation to calculate the contrast threshold and found that the contrast threshold of the target on the half-occluded region was higher than that on the 2D region. This elevation of contrast threshold indicates that interocular suppression of the half-occluded region occurs more frequently than that of the 2D region. We also refer to the monocular performance of the human visual system.