Assimilative and non-assimilative color spreading in the watercolor configuration.

Eiji Kimura,Mikako Kuroki

doi:10.3389/fnhum.2014.00722

Abstract

A colored line flanking a darker contour will appear to spread its color onto an area enclosed by the line (watercolor effect). The watercolor effect has been characterized as an assimilative effect, but non-assimilative color spreading has also been demonstrated in the same spatial configuration; e.g., when a black inner contour (IC) is paired with a blue outer contour (OC), yellow color spreading can be observed. To elucidate visual mechanisms underlying these different color spreading effects, this study investigated the effects of luminance ratio between the double contours on the induced color by systematically manipulating the IC and the OC luminance (Experiment 1) as well as the background luminance (Experiment 2). The results showed that the luminance conditions suitable for assimilative and non-assimilative color spreading were nearly opposite. When the Weber contrast of the IC to the background luminance (IC contrast) was smaller in size than that of the OC (OC contrast), the induced color became similar to the IC color (assimilative spreading). In contrast, when the OC contrast was smaller than or equal to the IC contrast, the induced color became yellow (non-assimilative spreading). Extending these findings, Experiment 3 showed that bilateral color spreading, i.e., assimilative spreading on one side and non-assimilative spreading on the other side, can also be observed in the watercolor configuration. These results suggest that the assimilative and the non-assimilative spreading were mediated by different visual mechanisms. The properties of the assimilative spreading are consistent with the model proposed to account for neon color spreading (Grossberg and Mingolla, 1985) and extended for the watercolor effect (Pinna and Grossberg, 2005). However, the present results suggest that additional mechanisms are needed to account for the non-assimilative color spreading.

Highlights

A colored line running parallel and contiguous to a darker contour will appear to spread its color onto a white area enclosed by the line (Figure 1A)
The results showed that when the luminance ratio between the inner contour (IC) and the outer contour (OC) (IC/OC luminance ratio) was the largest, which is a condition suitable for assimilative color spreading (Pinna et al, 2001; Devinck et al, 2005), the cancelation setting was closest to the opposite direction to the IC color in all stimulus conditions
Previous studies showed that the spreading was very weak when the OC luminance was in EXPERIMENT 2 In Experiment 2, we investigated color spreading in the watercolor configuration by manipulating the background luminance while keeping the IC/OC luminance ratio constant

Summary

Introduction

A colored line running parallel and contiguous to a darker contour will appear to spread its color onto a white area enclosed by the line (Figure 1A). This phenomenon is called the watercolor effect (Pinna et al, 2001). The magnitude of color spreading increased with the luminance ratio of the IC to the OC (Devinck et al, 2005; Devinck and Knoblauch, 2012) Based on these findings, Devinck et al (2005) suggested that the watercolor effect is mediated by luminance-dependent color mechanisms

Methods

Results

Conclusion