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

Abstract

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.

Take a look at Figure 1. What do you see? At first glance, it's just a grid of squares. But many people report seeing more structured shapes and patterns beyond the squares themselves—vertical lines, block letters and digits, and so on (see Figure 1). This is the phenomenon of “scaffolded attention,” where the squares seem to serve as a scaffold for seeing various patterns. These shapes and patterns have been described as “everyday hallucinations,” in that they do not correspond to any object cues in the incoming sensory information. This phenomenon seems to be a general feature of attention—occurring also in time and audition—and it has been associated with other measures of attention, such as attentional breadth (for a review, see Ongchoco & Scholl, 2023).

Figure 1.

(a) A blank white grid and (b) sample patterns.

In vision and in space, about 40% of observers will experience this phenomenon spontaneously (i.e., they report seeing various patterns upon being shown the grid without being prompted), while 78% can experience this when asked to try (try to see an H on the grid!). (And if you still cannot experience this phenomenon, see Ongchoco and Scholl (2022) for potential correlates of these individual differences.)

Previous work on this phenomenon has largely focused on whether and what observers see. An equally important aspect of observers’ perceptual reports, though, is how they see the squares, where the squares are described as sometimes subtly brighter or darker (for “shaders”), or other times “traced” out (for “bolders”). (Consider your experience with Figure 1. Are you a “shader” or a “bolder”?) These reports seem to allude to misperceptions or distortions to what it is that people are seeing. But just what do people mean by “shading” or “bolding” (i.e., how much brighter are these squares, or how bold are the lines?), and what factors underlie these experiences?

We showed 100 observers from the University of British Columbia Human Subject Pool a blank grid (as shown in Figure 1) for 30 s. They were told to “clear their minds and simply stare at the grid.” Afterwards, they reported which of three options most closely matched their experience: (a) a grid where some of the squares were shaded; (b) a grid where some of the lines were bolded; or (c) a blank grid. Observers who reported shading or bolding were taken to an interactive grid slider to recreate their visual experience. For shading, the slider controlled the squares’ color (Figure 2a), from a white grid (RGB 255, 255, 255) to a light gray overlay (RGB 190, 190, 190). For bolding (Figure 2b), the slider controlled the line widths, from 1 to 5 px.

Figure 2.

(a) Darkest shade and (b) maximum thickness.

Results revealed that 47% of observers were “hallucinators” (in that they reported spontaneously seeing shapes on the grid), and of this number, 36% reported seeing bolding. The average reported shading corresponded to an RGB value of (242, 242, 242) (Figure 3a), and the average reported bolding was 2.47 px (Figure 3b).

Figure 3.

(a) Average shading and (b) average bolding.

To understand the split in shading versus bolding experiences, we returned to the elements of the grid. Scaffolded attention has often been described as attention grouping the squares, yet the grid is composed of both squares and lines. Might tendencies towards shading versus bolding be driven in part by whether the squares versus the lines are initially selected? If so, we might be able to induce one type of experience over the other (i.e., bolding over shading) by modulating what elements are selected (i.e., lines over squares) in the first place. To test this, we considered a case where a subtle change to the stimulus itself should lead to the selection of the lines (instead of the squares).

Now consider any patterns you might experience in Figure 4. How do you see them? (A quick note from the authors: Your experience of the black grid may depend on the contrast settings of the screen on which you are reading this!) Prior research has shown that the visual system does not process light and dark the same way (e.g., Figure 5) due to asymmetrical processing of ON and OFF retinal ganglion cells (Lu & Sperling, 2012) and intraocular light scattering (Zavagno, 1999). In Figure 4, the white lines against the black should thus be more likely to be selected.

Figure 4.

A blank black grid.

Figure 5.

Hemholtz's “Irradiation Illusion” (see Tolansky, 1965). The right white square will seem larger than the left black square, despite being of the same size.

We showed observers the black grid and asked the same questions as in the white grid case. For shading (Figure 6a), the slider controlled the squares’ color from a black grid (RGB 0, 0, 0) to a light gray overlay (RGB 100, 100, 100). For bolding (Figure 6b), the slider controlled the line widths, from 1 to 5 px.

Figure 6.

(a) Lightest shade and (b) maximum thickness.

This time, results revealed that 64% of observers were hallucinators, and of this number, 89% reported seeing bolding. Fisher's exact test confirmed that the proportions of shaders to bolders were reliably different between the white and black grids (p < .001)—such that reversing the grid's contrast biased experiences towards bolding over shading. The average reported shading corresponded to an RGB value of (32, 32, 32) (Figure 7a), and the average reported bolding was 3.60 px (Figure 7b).

Figure 7.

(a) Average shading and (b) average bolding.

This inquiry was inspired by people's anecdotal reports of scaffolded attention—and here, we present at least one factor that modulates their experiences. Many questions remain, including whether individual differences contribute to one experience over another, and whether such experiences involve broader tendencies in visual processing. We note that shading and bolding are strikingly reminiscent of Ullman's visual routines (1984)—“coloring” and “tracing,” respectively—which might provide a hint towards understanding the underlying visual processes that give rise to everyday hallucinations in scaffolded attention.