摘要：

To investigate the factors determining the types of metacontrast masking function, masking functions were examined by varying either luminance or duration of mask stimulus (MS) under monoptic and dichoptic observations. Under dichoptic-variable luminance condition, U-shaped functions were obtained regardless of the MS luminance, but monotonic ones were found under monoptic with very high luminance. Under both observations with the variable duration condition, function changed from U-shaped to monotonic as the MS duration increased. Furthermore, when the test stimulus (TS) energy was equal to that of the MS, a long MS duration yielded a function close to monotonic one. It was suggested that types of metacontrast function might be determined by the MS duration and the duration ratio of TS to MS, not by the energy ratio.

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