The absence of a measurable “critical band” at low suprathreshold contrasts

Perceived spatial frequency shift after adaptation to compound gratings of two sinusoidals in phase or 180° out of phase

“…In this phenomenon, no phase effects were found, which was consistent with the results of Graham and Nachmias (1971), Graham et al (1978), Quick et al (1976) and Arend and Lange (1980), but inconsistent with the results of Sagi and Hochstein (1983). Sagi and Hochstein (1983) show that there are phase effects in discriminability of suprathreshold compound gratings which are composed of the fundamental and the third harmonic of relatively low spatial frequencies.…”

“…According to Graham and Nachmias (1971) and Graham, Robson, and Nachmias (1978), phase has no effect on the detection threshold of compound gratings. Quick, Hamerly, and Reichert (1976) and Arend and Lange (1980) have shown that, in suprathreshold conditions, contrast matches are insensitive to the relative phase of two widely separated components in compound gratings.…”

Spatial summation for complex bar patterns

“…Such a dependence makes it likely that the threshold is determined by the rtumurical rrwrg~ of the signal. Independent evidence for the (atter hypothesis has been presented by Quick et al ( 1976) and Mayhew and Frisby (1978). This hypothesis of power integration would imply incoherent summation and consequently we would predict that the stimulus structure is of minor importance for the summation effect.…”

“…not probability summation, because application of the convenient formalism due to Quick (1974) to our results leads to the expectation that the sensitivity should be propo~ional with a much higher power of the number of fields than is actually measured. Data from Quick et al (1976) and Mayhew and Frisby (1978) also point in this direction. They show that perceived contrast is proportional to the numerical energy of the signal.…”

“…If one regards the effects as the result of probability summation then a form of incoherent summation appears mandatory. Incoherent summation has been suggested by Quick et al (1976) on theoretical grounds. They also published experimental evidence that seems to favour the numerical energy (that is the incoherent sum) of the signal as the psychophysical variable corresponding to perceived contrast.…”