Sensitivity to contrast modulation: the spatial frequency dependence of second-order vision

Abstract

We consider the overall shape of the second-order modulation sensitivity function (MSF). Because second-order modulations of local contrast or orientation require a carrier signal, it is necessary to evaluate modulation sensitivity against a variety of carriers before reaching a general conclusion about second-order sensitivity. Here we present second-order sensitivity functions for new carrier types (low pass (1/f) noise, and high pass noise) and demonstrate that, when first-order artefacts have been accounted for, the shape of the resulting MSFs are similar to one another and to those for white and broad band noise. They are all low pass with a likely upper frequency limit in the range 10-20 c/deg, suggesting that detection of second-order stimuli is relatively insensitive to the structure of the carrier signal. This result contrasts strongly with that found for (first-order) luminance modulations of the same noise types. Here the noise acts as mask and each noise type masks most those frequencies that are dominant in its spectrum. Thus the shape of second-order MSFs are largely independent of the spectrum of their noise carrier, but first-order CSFs depend on the spectrum of an additive noise mask. This provides further evidence for the separation of first- and second-order vision and characterises second-order vision as a low pass mechanism.

The detection of the motion of contrast modulation: A parametric study

“…Furthermore, it also seems to be that any slight imbalance in the internal representation of the signal can have a strong effect on the resultant perception of direction and, in the present example, induce a powerful sense of reversal. It is worth noting that the window of visibility-that is, the spatiotemporal contrast sensitivity function-has also been measured for second-order modulation (Cropper, 1998;Schofield & Georgeson, 2003), although the second-order window of visibility is itself limited by the sensitivity to the first-order components of the pattern.…”

The Effect of White-Noise Mask Level on Sinewave Contrast Detection Thresholds and the Critical-Band-Masking Model

“…However, biological (De Valois, Albrecht, & Thorell, 1982;De Valois & De Valois, 1988) and psychophysical (Schofield & Georgeson, 2003;Solomon, 2000;Wilson, McFarlane, & Phillips, 1983) data suggest that visual filter bandwidth decreases as a function of spatial frequency tuning of the filter. These disagreements in the spatial vision literature about the variation of octave bandwidth with filter peak frequency make it necessary to disentangle the relationship between these two filter characteristics.…”

Texture Segregation and Texture Transparency

“…Hence, it has been proposed that non-linear transformation (e.g., rectification) of outputs from linear filters makes it possible to detect contrast-modulated gratings. Orientation and spatial frequency selectivity in the detection of contrast-modulated gratings were previously reported (Dakin & Mareschal, 2000;Nishida, Ledgeway, & Edwards, 1997;Prins & Mussap, 2000;Schofield & Georgeson, 2003;Sutter, Spering, & Chubb, 1995;Wenderoth, Clifford, & Wyatt, 2001).…”