Scaffolded attention in time: 'Everyday hallucinations' of rhythmic patterns from regular auditory beats

A regular grid (e.g. on a piece of graph paper) is made up of squares which (by definition) have no structure. When people stare at such a grid, however, they may nevertheless 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. This is the phenomenon of scaffolded attention, and recent work has demonstrated that this involves the creation of bona fide object representations (e.g. that enjoy 'same-object advantages'). Is this an intrinsically visuospatial phenomenon, or might it rather reflect a much more general effect of perceiving structure from regular scaffolds, which could also occur in other dimensions or modalities? Here we show for the first time that there is also robust scaffolded attention in time: a regular series of tones (as might come from a metronome) has no structure beyond the 'beats' themselves, but people nevertheless hear a shifting array of structured rhythms - a phenomenon that doesn't occur when listening to silence. We demonstrate (in tests of temporal 'same-event advantages') that this (entirely internal) process gives rise to bona fide event representations. Thus the relationship between attention and events is bidirectional: event structure can guide attention, but attention can also create event structure in the first place. In this way we show how 'everyday hallucinations' of rhythmic patterns can arise in the absence of explicit sensory structure.