Contrast sensitivity indicates processing level of visual illusions.

Abstract

A nearly linear contrast response function (CRF) is found in the lower level striate cortex whereas a steep, nonlinear increase at lower contrasts that gradually increases toward response saturation for higher contrasts is found in the higher level extrastriate cortex. This change of CRFs along the ventral cortical pathway indicates a shift from stimulus- and energy-dependent coding at lower levels to percept- and information-dependent coding at higher levels. The increase of nonlinearity at higher levels optimizes the extraction of perceptual information by amplifying responses to the ubiquitous low-contrast inputs in the environment. We used this difference of CRFs between lower and higher levels, particularly at lower contrasts (.0 to .30), as a tool to investigate examples of 2 lower level (simultaneous brightness and simultaneous tilt) and 2 higher level (Poggendorff and Ponzo) illusions. As predicted, the Poggendorff and Ponzo illusions yielded strong nonlinear increases in their CRFs compared to the more linear functions found for the simultaneous-brightness and simultaneous-tilt illusions. We conclude that the Poggendorff-Ponzo illusions rely more heavily on high-level, percept-dependent cortical processing than do the simultaneous-brightness-simultaneous-tilt illusions and, more generally, that differences between contrast-dependent changes may be a useful tool in determining the relative level of cortical processing of many other visual effects. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Can Contrast-Response Functions Indicate Visual Processing Levels?

“…Another implication is that the proposed approach supports applying our rationale to studying the comparative processing levels of many additional visual phenomena such as visual illusions. We [93] are currently applying it to investigations of the processing levels of simultaneous brightness induction, a version of the tilt illusion different from the one used by Pearson and Clifford, the Ponzo illusion, as well as the White effect [94]. Using our version of the simultaneous tilt illusion, we replicated Pearson and Clifford’s tilt-illusion results obtained when the inducer was visible (see Figure 3).…”

Gestalts at threshold could reveal Gestalts as predictions

“…Peak differences between striate and extra-striate CRFs were found around the time where striate cortex responses start to saturate (for more comprehensive figures, see also Brown et al, 2018). In this context, one can interpret the saturation of extra-striate activity in the CRF as the peak of information-driven/percept-driven processing (as opposed to energy-driven/stimulus-driven processing; e.g., 67 , 70 ). Here we propose to extrapolate over the methodological differences between our study and Hall et al 85 , and to interpret this result as indicating that (1) peak Gestaltness is observed when the visual system switches from stimulus- and energy-dependent processing to percept- and information-dependent processing and that (2) Gestalts differentially engage higher-order visual processing areas, even when dealing with “pure Gestalt” (i.e., the two-dot pure emergent feature stimuli).…”

“…This supports the well-established notion that, along the hierarchy of cortical visual processing, responses change from being dependent on stimulus energy (e.g., contrast, size) at low levels to being percept and information-dependent at higher-order areas (for other examples, see 67 – 69 . In the field of pure psychophysics, Brown et al 70 found that the changes in illusion magnitude as a function of stimulus contrast were linear for illusions that relied more strongly on low processing levels (e.g., simultaneous brightness and simultaneous tilt) and nonlinear for illusions that rely more strongly on contextual information and higher processing levels (e.g., the Ponzo and Poggendorff illusions).…”

Illusory size determines the perception of ambiguous apparent motion

“…But there is recent evidence that even simpler versions depend on higherlevel information. Brown, Breitmeyer, Hale, and Plummer (2018) measured the contrast response function (CRF) for the traditional simple Ponzo illusion, i.e., how the magnitude of the illusion changes as a function of the contrast of inducing stimuli (i.e., the converging lines). They found non-linear changes in the CRF for the Ponzo illusion, indicating a dependence on higher-level perceptual coding (e.g., perceived size and distance).…”