Hallucinating visual structure: Individual differences in 'scaffolded attention'.

Our percepts usually derive their structure from particular cues in the incoming sensory information, but this is not so in the phenomenon of scaffolded attention - where shifting patterns of attention give rise to 'everyday hallucinations' of visual structure even in the absence of sensory cues. When looking at a piece of graph paper, for example, the squares are all identical - yet many people see a shifting array of structured patterns such as lines, crosses, or even block-letters - something that doesn't occur when staring at a blank page. We have informally noted that scaffolded attention is a widely but not universally shared phenomenon - with some people spontaneously experiencing such percepts (even without instruction), others seeing such 'phantom' structures only when actively trying to so, and still others never having such experiences at all. Accordingly, the present study assessed the prevalence of scaffolded attention - both as an ability, and a spontaneous phenomenon. These results were then correlated with several measures of imagery and attention, in an attempt to explain the nature and origin of such individual differences. 40% of observers experienced scaffolded attention spontaneously, and 78% did so when trying - and these differences were uniquely modulated by certain measures of attention (such as attentional breadth, as measured by the 'functional field of view'), but not by measures of the vividness or spontaneity of mental imagery. These results inspire an explanation for scaffolded attention based on spontaneous perceptual grouping.