Are you a visual “shader” or a “bolder”? Different visual routines create everyday hallucinations in “scaffolded attention”

The colors and lines that compose perceptual experience result from the interplay between visual processing pathways and the light that hits the retina. So it is striking that many individuals seem to also experience these visual properties even in the absence of explicit sensory cues-as in the phenomenon of "scaffolded attention." When observing a uniform grid of squares, people report perceiving the squares as grouped into shapes or patterns, where the squares sometimes appear brighter or colored (for "shaders"), or bolded or outlined (for "bolders"). With 100 observers, we used an interactive grid to characterize the prevalence and magnitude of these experiences. Results showed that people's experiences could be modulated by grid contrast, that is, 89% of hallucinators reporting "bolding" on a black grid, while only 36% on a white one. Thus, stimulus factors may influence what gets selected-the squares (for shaders) or the lines (for bolders)-as the raw material for "everyday hallucinations" in scaffolded attention.