Simultaneous Color Contrast Increments with Complexity and Identity of the Target Stimulus.

Simultaneous color contrast is a perceptual phenomenon in which a target stimulus appears to change its hue due to color induction from the surrounding background. In this study, we investigated whether this phenomenon is influenced by the structural complexity and identity of the stimuli used. In Experiment 1, we created two sets of stimuli varying in structural complexity and asked participants to perform a color-matching task on the achromatic target. Low-complexity targets consisted of simple squares, while high-complexity targets were stylized cars. The results showed that high-complexity stimuli triggered stronger color induction from the background and exhibited greater interindividual variation in perceived color saturation. Conversely, low-complexity stimuli were predominantly perceived as achromatic across all participants. In Experiment 2, we further explored whether these effects were influenced by differences in the stimuli's topology and identity. Topological factors were controlled by ensuring similar organizations of stimulus elements across conditions, while the role of stimulus identity was examined by including a condition in which the high-complexity stimuli from Experiment 1 were presented in a scrambled arrangement, preventing recognition. The results demonstrated that color contrast increased with the complexity of the stimuli but also highlighted the role of identity, as the condition where the car was recognizable elicited the strongest color induction. We conclude that simultaneous color contrast is strengthened by factors that pertain to both the complexity of the stimuli used and their identity.