The present psychophysical experiments provide evidence for the existence of a variety of
detectors responding optimally to lines, edges or gratings. Their existence is revealed by …

The orientation selectivity of grating and line detectors is determined by subthreshold
summation; that is, the reduction in contrast threshold of a grating or line test stimulus due to …

Contrast thresholds for circular J 0 targets and rectilinear sine-wave gratings behave quite
differently as functions of spatial frequency; the ratio of the two thresholds varies as the first …

Results from three experiments using spatial forced-choice techniques show that an illusory
contour improves the detectability of a spatially superimposed, thin subthreshold line of …

It is now generally accepted that several mechanisms mediate contrast detection at
threshold. Many attempts to measure the bandwidths of these mechanisms using …

Forced-choice psychometric functions were determined for the detection of sinewave
gratings and contrast discrimination of near-threshold gratings at spatial frequencies of 0.5 …

The frequent current use in probability summation calculations of equations of the form. P=
1−(1− γ) exp [−(I/α) β] to represent the psychometric function for contrast detection is based …

The contrast thresholds for sine-wave profile gratings were measured as a function of both
the length of the bars and the number of bars of the grating. These factors were found to …

Simple reaction time measurements were made for a wide range of contrast values and
spatial frequencies of sinusoidal gratings. For every spatial frequency, reaction time …

Contrast sensitivity at different positions in the visual field has been measured at various
spatial frequencies using a patch of grating suitably vignetted to give a stimulus localized in …