Blackwell K T
Environmental Research Institute of Michigan, Arlington, VA 22209, USA.
Vision Res. 1998 Jan;38(2):267-80. doi: 10.1016/s0042-6989(97)00130-2.
Models of the dipper effect seen in contrast discrimination experiments predict that small amounts of noise should facilitate detection of a subthreshold sinusoidal grating. Although facilitation of chromatic sine waves has been measured with chromatic or luminance noise, a facilitory effect of luminance sinusoidal gratings has not been measured, most likely because the stimulus characteristics were not tuned for revealing facilitation. The present study measures contrast detection thresholds (CDTs) of sinusoidal gratings in two-dimensional, static, band-limited white noise and low-pass and high-pass filtered noise using a two-interval forced-choice paradigm. The results show facilitation in near threshold white noise of middle frequency sinusoidal gratings, and facilitation in filtered noise of sinusoidal gratings whose frequency is far outside the pass band of the noise. Based on these results, a model of contrast detection thresholds is modified such that the facilitation is attributed to reduced observer uncertainty caused by small amounts of noise.
在对比度辨别实验中观察到的勺形效应模型预测，少量噪声应有助于检测阈下正弦光栅。虽然已用彩色或亮度噪声测量了彩色正弦波的促进作用，但尚未测量亮度正弦光栅的促进作用，这很可能是因为刺激特性未针对揭示促进作用进行调整。本研究使用双间隔强迫选择范式测量了二维、静态、带限白噪声以及低通和高通滤波噪声中正弦光栅的对比度检测阈值（CDT）。结果表明，中频正弦光栅在接近阈值的白噪声中存在促进作用，而频率远在噪声通带之外的正弦光栅在滤波噪声中存在促进作用。基于这些结果，对对比度检测阈值模型进行了修改，使得促进作用归因于少量噪声导致的观察者不确定性降低。
